Prior to the emergence of geotechnical engineering as an applied science, engineers, architects, and builders relied to a large extent on nearby edifices when selecting and designing a support system for a structure. Accepting that soil profiles and rock masses present in nature are seldom homogeneous, elastic and isotropic, the potential problems of this approach are obvious. And yet degrees of the above thinking still prevail!

Overcoming biased foundation directives can be demanding but also very rewarding for a geotechnical engineer, and GeoStructures is truly at the forefront of this endeavor. We have utilized innovative foundation systems on numerous projects with difficult subsurface conditions under opposition and local misconceptions.

It is our conviction that every project no matter how large or small can benefit from a thorough subsurface investigation due to its unique set of conditions and influencing geologic factors. We are experienced in the following aspects of site characterization.

• Test Borings and Test Pits.
• Standard Penetration Testing (SPT).
• Cone Penetrometer Testing (CPT).
• Seismic Cone Penetration Testing (SCPT).
• Undisturbed (Shelby) Tube Sampling of Soils.
• Rock Coring.
• Air Rotary (Percussion) Drilling.
• Direct Push or “Geoprobe” Sampling.
• Electromagnetic (EM), Seismic, Ground Penetrating Radar (GPR) & Microgravity Surveys.
• Fracture Tracing and Photogrammetry (Stereo Pairs of Aerial Photos).
• Geologic Mapping.
• Geotechnical Instrumentation.
• Hydrogeologic Studies: Piezometers and Monitoring Wells.
• Laboratory Testing Services.
• Rock Structure Measurements (Strike and Dip of Beds, Joints, Faults, etc.).

Our extensive expertise in soil-structure interaction, constitutive modeling and the geotechnical applications of the finite element method (FEM) enable us to better understand and optimize complex foundations, braced excavations, slopes and retaining systems, embankments, dams and pavements. Yet no amount of modeling and sophisticated analyses can account for missing key subsurface factors. Therefore, before accurately modeling any given project, we place significant emphasis on subsurface site characterization to identify its critical and unique subsurface factors. This is the main distinguishing feature of our work and what truly sets us apart. Our expertise in this area of practice includes:

• Site specific response spectra and soil dynamic analysis.
• Braced excavations.
• Pavement stress analysis and mechanistic design.
• Steady state seepage and transient flow analysis.
• Groundwater modeling and contaminant transport.
• Machine foundations.
• Lateral capacity of piles and caissons.
• Stress deformation behavior of foundation systems.
• Soft and hard ground tunneling.

Loma Prieta 1989 USGS Gilroy #1 Station	Ground Acceleration Spectrum

Depending on structure type, height, sensitivity to settlement, seismic zone, site conditions, and other factors, the cost of a foundation as a percentage of total project cost can vary dramatically. Our goal as geotechnical engineers is to develop technically sound support systems while minimizing costs. Optimum foundation designs do not naturally arise from equations or design charts; they are a product of outstanding engineering judgment developed through years of experience in the design and construction fields.

When multiple foundation types seem equally feasible, selecting the best system for the job can be challenging but also very rewarding. Responsible design optimization requires us to look beyond subsurface investigations and routine cost estimates. Our engineers are skilled at asking the right questions about site grading, construction sequencing, schedule, abilities of local construction forces, and other project-specific variables that could affect design or construction of a foundation.

Innovative yet practical solutions are integrated by GeoStructures into every foundation design and evaluation project. Our experience encompasses all types of support systems and load testing, including: shallow foundations; mat footings; driven, drilled, jetted, bored, auger cast, precast, and cast-in-place piles; and drilled piers or caissons. Our capabilities extend beyond standard services to soil-structure interaction modeling and comprehensive foundation design and inspection.

When it comes to rehabilitation and underpinning of existing foundations, our strength in finite element analysis enables us to accurately model the foundation behavior and establish the most reliable rehabilitation scheme. In coordination with the owner, engineer or architect, we often design the selected rehabilitation system, provide complete drawings and specifications, and monitor its implementation. This gives us significant advantages over proprietary contractors who may tend to utilize one system or another without due evaluation and cost comparison.

Construction monitoring and materials testing are the bridge between design and a safe, economical, high quality, completed project. GeoStructures provides QA/QC and construction-related services to owners, architects, engineers, design/build contractors, general contractors, developers, and state and federal highway and transportation agencies. All of our field personnel are experienced and certified engineers or engineering geologists. Our QA/QC services cover:

• Shallow Foundations.
• Subgrade Proofrolling.
• Fill Compaction Testing.
• Plate Load Testing of Subgrade.
• Asphalt and Rigid Pavements.
• Drilled Shafts (Caissons).
• Pile Driving and Load Testing (Static and Dynamic).
• Cast in Place Concrete.
• Masonry, Grout, Mortar and Reinforcement.
• Precast Concrete Connections.
• Structural Steel.
• Slab Flatness and Levelness (F-number).
• Vibration and Noise Monitoring.
• Subgrade Lime and Cement Stabilization.
• Geomembrane Liner Installation and Testing.

As long, narrow, nearly two-dimensional elements, highways and other transportation corridors traverse a variety of terrain, topography, geology, and cultural settings. Among public works projects, transportation-related infrastructure ones involve, perhaps, the greatest diversity of structures.

It is not uncommon for a single interstate segment measuring only a few miles to have bridges, tunnels, viaducts, overpasses, underpasses, deep cuts, high fill embankments, natural soil and rock slopes, steep reinforced slopes, earth retaining systems, shoring, and buried culverts in either rural or urban settings. In fact, most of the professional services we offer at GeoStructures can be covered under this category.

Our engineers possess the breadth of experience and qualifications to handle the many geotechnical and foundation related challenges posed by bridge and highway projects, and we have a proven record with PennDOT, DelDOT, NJDOT, SEPTA, and the Pennsylvania Turnpike Commission. Some of our most innovative engineering and design work have been incorporated into major transportation projects.

Without exception, today’s major highways incorporate some form of concrete (rigid) or asphalt (flexible) pavements. While Roman engineers are generally credited with the first true concrete more than 2,000 years ago, hot mix asphalt technology advanced gradually, with landmark innovations and widespread use occurring over the past 150 years or so. GeoStructures provides complete pavement-related services, including investigation, design, rehabilitation, and evaluation of both rigid and flexible pavements in accordance with AASHTO and state DOT standards. A list of our pavement-related services follows.

• California Bearing Ratio (CBR) and Resilient Modulus (M R) Testing.
• Clegg Impact Hammer (CIH) and Dynamic Cone Penetrometer (DCP) Testing .
• Condition Surveys and Assessment of Remaining Life.
• Coring, Test Borings, and Subgrade Sampling .
• Finite Element Analysis of Pavement Structures and Subgrade.
• Extraction Testing of Pavement Cores.
• Falling Weight Deflectometer (FWD) .
• Geotextiles, Geomebrances, Geogrid, and Steel Mesh Applications.
• Lime and Cement Stabilization of Subbase and Subgrade.
• Rehabilitation Alternatives and Life Cycle Cost Analysis.
• Reflective Cracking Mitigation.
• Laboratory and In-Situ Pavement Permeability Testing.
• Frost Behavior of Subbase and Subgrade Materials.
• Forensic Studies of Premature Pavement Failures.

According to the National Landslide Hazards Program (NLHP) administered by the USGS, landslides constitute a major geologic hazard because they are widespread and can be quite severe; they occur in all 50 states and U.S. territories and cause an average of $1 to 2 billion in damages each year. GeoStructures is experienced in the design, evaluation and rehabilitation of a full range of earth/rock slopes and retaining systems for transportation facilities, commercial sites, and residential developments. In addition to competency in traditional limit-equilibrium analysis, our strength in soil-structure interaction modeling and use of FEM enables us to gain a deeper understanding of complicated slopes and earth retaining systems.
In the area of retaining systems, our engineers were among the first in Pennsylvania (late 1980s) to design geogrid-reinforced retaining walls, structures commonly referred to today as mechanically stabilized earth (MSE) walls or segmental retaining walls (SRW). A summary of our capabilities in the design of slope and retaining systems follows.

• Geogrid-Reinforced Retaining Walls and Steep Slopes (1H:1V or steeper).
• Geosynthetic Erosion Control and Vegetative Mats.
• Mechanically Stabilized Earth (MSE) Walls .
• Sheet Pile Walls (Cantilever, Braced, or with Tie-Backs).
• Soil Nailing, Soil Anchors and Rock Anchors .
• Post and Panel Walls .
• Rock Cut Slopes .
• Concrete Retaining Walls (Gravity or Cantilever).
• Gabion and Boulder Retaining Walls.
• Coffer Dams.

Of the nearly 80,000 dams listed in the National Dam Inventory, about 10,000 are identified as high-hazard structures, which means their failure could result in loss of life, significant property damage, critical infrastructure disruption, or severe environmental damage. According to the American Society of Civil Engineers (ASCE) 2005 Report Card for America’s Infrastructure, more than 3,500 of the high-hazard dams are unsafe and a staggering $10.1 billion would be needed over the next 12 years to address all of the critical non-federal ones. The Dam Safety and Security Act enacted by Congress in 2002 fosters coordination among the Federal Emergency Management Agency (FEMA) and state dam safety programs. It mandates periodic inspection, maintenance, and monitoring of dams as well as Emergency Action Plans (EAPs) at all levels of government to deal with a potential catastrophe.

Our geotechnical engineers are qualified to inspect and evaluate dams under federal and state guidelines. In this capacity we have assisted owners with code compliance by performing computer-aided dam break and flood analyses, the results of which serve as the basis for an EAP. Past experience with the rehabilitation of earth and concrete dams has covered crest heightening, foundation design for new spillways and fish passageways, and enhanced downstream erosion protection. Most projects demand expertise in geotechnical instrumentation and interpretation of seepage, piping, drawdown, and stability conditions. Our ability to utilize the results of steady-state seepage (flow net analyses) as input to effective stress FEM is especially useful in this regard.

The design and inspection of liner systems for wastewater lagoons and ponds of all types require expertise in geosynthetic materials, drainage problems, and other geotechnical issues. Some factors considered by GeoStructures on past projects to select the optimal liner are end use, geologic setting, water level fluctuations, reactive chemical effluent, uplift, vegetation, and the risk of karst-related dropouts. Regardless of type, however, attention to detail is critical, with anchor trenches, field seaming, curtain drains, and pipe penetrations playing major roles in long-term performance. QA/QC during construction must address the following items.

• Subgrade Preparation.
• Control of Blasting Operations to Prevent Heave.
• Conformance Testing of Geosynthetics (Field and Laboratory).
• Field Seaming .
• Nondestructive and Destructive Seam Testing.
• Patching and Repair of Damaged Sections .
• As-Built Panel Layout .
• Placement and Compaction of Soil Cover.

Legends of disappearing streams and underground lakes and rivers are common in karst regions, where sinkholes seem to appear overnight to swallow a building or close a commuter roadway. Sinkholes are a natural consequence of soil loss into underlying bedrock solution openings that have formed over eons of time. Erosion domes are the most dramatic and potentially damaging. These features form in cohesive soils and progress upward like “bubbles” through incremental roof collapse until they reach the ground surface. Roof collapse occurs when the width of an underground opening exceeds the ability of the overlying material to arch across it. This process is similar to that of mine subsidence. With water as the accelerator of roof collapse, it follows that areas of focused infiltration such as recently cleared construction sites, drainage channels, and unlined stormwater basins are especially vulnerable to sinkholes.

Chemical decomposition of carbonate rocks such as limestone and dolomite is a natural process. Corrosive agents include rainwater made slightly acidic by dissolved carbon dioxide or groundwater containing dissolved hydrogen sulfide gas from the breakdown of organics. Contrary to popular belief, normal fluctuations in pH—natural or artificial—have virtually no effect on this process over the lifespan of a structure even though some building codes reflect this misconception. In humid climates of the eastern United States fracture surface denudation is only 1 to 1-½ in. per 1,000 years. At this rate, it would take at least 100,000 years to form a 12-ft wide slot in the rock and millions of years to create extensive underground caverns!

Building with confidence in karst demands detailed subsurface investigations to identify incipient sinkholes and characterize a site’s unique hydrogeologic factors. Universal tools of intrusive investigation include borings, percussion probes, and test pits. Recognizing that high angle discontinuities are more vulnerable to large openings, geologic mapping of rock exposures on or near a job site for weathering and fracturing can provide insight into the alignment of underground slots in the bedrock. In the absence of visible outcrops and as a complement to geologic mapping, aerial photo stereo pairs can be obtained for many sites. Such photos are examined for fracture traces—recognizable as lineaments of dark ground caused by deep weathering, increased moisture and dense vegetation. Geophysical tools may also be applied to obtain 2-D profiles of the ground and rock between discrete borings. Effective techniques include microgravity, electromagnetic (EM), DC resistivity, and seismic refraction surveys.

Methods of sinkhole repair and ground stabilization vary depending on structural importance, working constraints, soil type, depth to rock, and depthto groundwater. GeoStructures has utilized and refined a cost-effective, shallow bridging remediation technique. In this approach, raveled soils are replaced with a reinforced plug of geosynthetics, riprap, and stone. Deep, high-risk features hampered by shallow groundwater or tight working conditions may require compaction grouting, which is the injection of low slump grout into the ground and rock under high pressure to fill voids and compact raveled soils. Both types of repairs have been successful on numerous private as well as PennDOT and Pennsylvania Turnpike projects.

Depending on structure type, height, sensitivity to settlement, seismic zone, site conditions, and other factors, the cost of a foundation as a percentage of total project cost can vary dramatically. Our goal as geotechnical engineers is to develop technically sound support systems while minimizing costs. Optimum foundation designs do not naturally arise from equations or design charts; they are a product of outstanding engineering judgment developed through years of experience in the design and construction fields.

When multiple foundation types seem equally feasible, selecting the best system for the job can be challenging but also very rewarding. Responsible design optimization requires us to look beyond subsurface investigations and routine cost estimates. Our engineers are skilled at asking the right questions about site grading, construction sequencing, schedule, abilities of local construction forces, and other project-specific variables that could affect design or construction of a foundation.

Innovative yet practical solutions are integrated by GeoStructures into every foundation design and evaluation project. Our experience encompasses all types of support systems and load testing, including: shallow foundations; mat footings; driven, drilled, jetted, bored, auger cast, precast, and cast-in-place piles; and drilled piers or caissons. Our capabilities extend beyond standard services to soil-structure interaction modeling and comprehensive foundation design and inspection.

When it comes to rehabilitation and underpinning of existing foundations, our strength in finite element analysis enables us to accurately model the foundation behavior and establish the most reliable rehabilitation scheme. In coordination with the owner, engineer or architect, we often design the selected rehabilitation system, provide complete drawings and specifications, and monitor its implementation. This gives us significant advantages over proprietary contractors who may tend to utilize one system or another without due evaluation and cost comparison.

Deep room-and-pillar mines have been active in Pennsylvania’s coalfields since the late 1700s. Sinking of the ground surface above the mines occurs as long troughs or local circular potholes. Troughs are caused by the crushing failure of coal pillars or the punching of coal pillars into the underclay (fireclay) of a mine floor. Potholes form when a mine roof collapses and the overburden is less than about 50 ft. Similar to dome sinkholes in karst regions, potholes usually occur suddenly and can cause severe structural damage.

Factors controlling mine subsidence include height of the mined-out coal bed, pillar size, width between pillars, overburden thickness, and rock strength. According to the Ohio Division of Geological Survey, the potential area of subsidence extends beyond the extraction area along a 35° angle of projection, called the angle of draw. The deeper the mine, the larger the area potentially affected by mine subsidence at the surface.

Site investigations and risk assessments start with research of historic mine maps kept in the Department of the Interior’s Office of Surface Mining (OSM). This is followed by a program of deep test borings, geologic mapping, and geophysics to further delineate subsurface openings. Examples of geophysical techniques are borehole tomography and cross-hole seismic surveys. Detailed subsurface investigations enable different levels of risk to be assigned based on various controlling parameters, such as the ratio of overburden to void height. An added comfort level can be gained by using FEM to model underground stresses and deformations due to surface loads and site-specific subsurface factors.

Commonly employed methods for stabilizing the ground above old mines involve compaction grouting—a technique similar to that used to repair karst-related sinkholes. Low slump concrete mixes may be initially injected as a barrier in advance of using less expensive, high slump and low strength cement and fly ash as production grout. The grout fills mine openings in the area of the collapse and also builds columns from the floor of the mine to the ground surface.

Scarce available open land in densely developed metropolitan areas and the inherent challenges posed by undocumented fills, demolition debris or soft floodplain deposits are a few of the driving forces behind recent innovations in soil improvement. With the advent of new technologies, sites ignored in the past can now be developed using economical shallow foundations and conventional slab on grade instead of costly pile or caisson foundations and structural ground floor slabs. Detailed subsurface investigations are critical to the selection and proper use of any soil improvement technology.
Options for large-scale, in-place densification of granular soils include intensive proofrolling, dynamic compaction, and other densification/compaction techniques. Post-construction settlement of soft, saturated silt and clay deposits, on the other hand, can be mitigated through preloading. For marginal sites, a combination of methods may be the best approach. Lightweight fills can also be used to actually offset structural loads and essentially “float” a building. GeoStructures has extensive experience in the design, testing and monitoring of the following soil improvement methods:

• Intensive Proofrolling to Deeply Propagate Compaction Energy.
• Ballast-Stabilized Footing Excavations.
• Compaction and Low Mobility Grouting.
• Deep Dynamic Compaction.
• Vibro-Compaction and Vibro-Replacement.
• Preloading and Sand or Wick Drains.
• Cellular Concrete or Geofoam.
• Lightweight Fill.

Prior to the emergence of geotechnical engineering as an applied science, engineers, architects, and builders relied to a large extent on nearby edifices when selecting and designing a support system for a structure. Accepting that soil profiles and rock masses present in nature are seldom homogeneous, elastic and isotropic, the potential problems of this approach are obvious. And yet degrees of the above thinking still prevail!

Overcoming biased foundation directives can be demanding but also very rewarding for a geotechnical engineer, and GeoStructures is truly at the forefront of this endeavor. We have utilized innovative foundation systems on numerous projects with difficult subsurface conditions under opposition and local misconceptions.

It is our conviction that every project no matter how large or small can benefit from a thorough subsurface investigation due to its unique set of conditions and influencing geologic factors. We are experienced in the following aspects of site characterization.

• Test Borings and Test Pits.
• Standard Penetration Testing (SPT).
• Cone Penetrometer Testing (CPT).
• Seismic Cone Penetration Testing (SCPT).
• Undisturbed (Shelby) Tube Sampling of Soils.
• Rock Coring.
• Air Rotary (Percussion) Drilling.
• Direct Push or “Geoprobe” Sampling.
• Electromagnetic (EM), Seismic, Ground Penetrating Radar (GPR) & Microgravity Surveys.
• Fracture Tracing and Photogrammetry (Stereo Pairs of Aerial Photos).
• Geologic Mapping.
• Geotechnical Instrumentation.
• Hydrogeologic Studies: Piezometers and Monitoring Wells.
• Laboratory Testing Services.
• Rock Structure Measurements (Strike and Dip of Beds, Joints, Faults, etc.).

Our extensive expertise in soil-structure interaction, constitutive modeling and the geotechnical applications of the finite element method (FEM) enable us to better understand and optimize complex foundations, braced excavations, slopes and retaining systems, embankments, dams and pavements. Yet no amount of modeling and sophisticated analyses can account for missing key subsurface factors. Therefore, before accurately modeling any given project, we place significant emphasis on subsurface site characterization to identify its critical and unique subsurface factors. This is the main distinguishing feature of our work and what truly sets us apart. Our expertise in this area of practice includes:

• Site specific response spectra and soil dynamic analysis.
• Braced excavations.
• Pavement stress analysis and mechanistic design.
• Steady state seepage and transient flow analysis.
• Groundwater modeling and contaminant transport.
• Machine foundations.
• Lateral capacity of piles and caissons.
• Stress deformation behavior of foundation systems.
• Soft and hard ground tunneling.

Loma Prieta 1989 USGS Gilroy #1 Station	Ground Acceleration Spectrum

Depending on structure type, height, sensitivity to settlement, seismic zone, site conditions, and other factors, the cost of a foundation as a percentage of total project cost can vary dramatically. Our goal as geotechnical engineers is to develop technically sound support systems while minimizing costs. Optimum foundation designs do not naturally arise from equations or design charts; they are a product of outstanding engineering judgment developed through years of experience in the design and construction fields.

When multiple foundation types seem equally feasible, selecting the best system for the job can be challenging but also very rewarding. Responsible design optimization requires us to look beyond subsurface investigations and routine cost estimates. Our engineers are skilled at asking the right questions about site grading, construction sequencing, schedule, abilities of local construction forces, and other project-specific variables that could affect design or construction of a foundation.

Innovative yet practical solutions are integrated by GeoStructures into every foundation design and evaluation project. Our experience encompasses all types of support systems and load testing, including: shallow foundations; mat footings; driven, drilled, jetted, bored, auger cast, precast, and cast-in-place piles; and drilled piers or caissons. Our capabilities extend beyond standard services to soil-structure interaction modeling and comprehensive foundation design and inspection.

When it comes to rehabilitation and underpinning of existing foundations, our strength in finite element analysis enables us to accurately model the foundation behavior and establish the most reliable rehabilitation scheme. In coordination with the owner, engineer or architect, we often design the selected rehabilitation system, provide complete drawings and specifications, and monitor its implementation. This gives us significant advantages over proprietary contractors who may tend to utilize one system or another without due evaluation and cost comparison.

Construction monitoring and materials testing are the bridge between design and a safe, economical, high quality, completed project. GeoStructures provides QA/QC and construction-related services to owners, architects, engineers, design/build contractors, general contractors, developers, and state and federal highway and transportation agencies. All of our field personnel are experienced and certified engineers or engineering geologists. Our QA/QC services cover:

• Shallow Foundations.
• Subgrade Proofrolling.
• Fill Compaction Testing.
• Plate Load Testing of Subgrade.
• Asphalt and Rigid Pavements.
• Drilled Shafts (Caissons).
• Pile Driving and Load Testing (Static and Dynamic).
• Cast in Place Concrete.
• Masonry, Grout, Mortar and Reinforcement.
• Precast Concrete Connections.
• Structural Steel.
• Slab Flatness and Levelness (F-number).
• Vibration and Noise Monitoring.
• Subgrade Lime and Cement Stabilization.
• Geomembrane Liner Installation and Testing.

As long, narrow, nearly two-dimensional elements, highways and other transportation corridors traverse a variety of terrain, topography, geology, and cultural settings. Among public works projects, transportation-related infrastructure ones involve, perhaps, the greatest diversity of structures.

It is not uncommon for a single interstate segment measuring only a few miles to have bridges, tunnels, viaducts, overpasses, underpasses, deep cuts, high fill embankments, natural soil and rock slopes, steep reinforced slopes, earth retaining systems, shoring, and buried culverts in either rural or urban settings. In fact, most of the professional services we offer at GeoStructures can be covered under this category.

Our engineers possess the breadth of experience and qualifications to handle the many geotechnical and foundation related challenges posed by bridge and highway projects, and we have a proven record with PennDOT, DelDOT, NJDOT, SEPTA, and the Pennsylvania Turnpike Commission. Some of our most innovative engineering and design work have been incorporated into major transportation projects.

Without exception, today’s major highways incorporate some form of concrete (rigid) or asphalt (flexible) pavements. While Roman engineers are generally credited with the first true concrete more than 2,000 years ago, hot mix asphalt technology advanced gradually, with landmark innovations and widespread use occurring over the past 150 years or so. GeoStructures provides complete pavement-related services, including investigation, design, rehabilitation, and evaluation of both rigid and flexible pavements in accordance with AASHTO and state DOT standards. A list of our pavement-related services follows.

• California Bearing Ratio (CBR) and Resilient Modulus (M R) Testing.
• Clegg Impact Hammer (CIH) and Dynamic Cone Penetrometer (DCP) Testing .
• Condition Surveys and Assessment of Remaining Life.
• Coring, Test Borings, and Subgrade Sampling .
• Finite Element Analysis of Pavement Structures and Subgrade.
• Extraction Testing of Pavement Cores.
• Falling Weight Deflectometer (FWD) .
• Geotextiles, Geomebrances, Geogrid, and Steel Mesh Applications.
• Lime and Cement Stabilization of Subbase and Subgrade.
• Rehabilitation Alternatives and Life Cycle Cost Analysis.
• Reflective Cracking Mitigation.
• Laboratory and In-Situ Pavement Permeability Testing.
• Frost Behavior of Subbase and Subgrade Materials.
• Forensic Studies of Premature Pavement Failures.

According to the National Landslide Hazards Program (NLHP) administered by the USGS, landslides constitute a major geologic hazard because they are widespread and can be quite severe; they occur in all 50 states and U.S. territories and cause an average of $1 to 2 billion in damages each year. GeoStructures is experienced in the design, evaluation and rehabilitation of a full range of earth/rock slopes and retaining systems for transportation facilities, commercial sites, and residential developments. In addition to competency in traditional limit-equilibrium analysis, our strength in soil-structure interaction modeling and use of FEM enables us to gain a deeper understanding of complicated slopes and earth retaining systems.
In the area of retaining systems, our engineers were among the first in Pennsylvania (late 1980s) to design geogrid-reinforced retaining walls, structures commonly referred to today as mechanically stabilized earth (MSE) walls or segmental retaining walls (SRW). A summary of our capabilities in the design of slope and retaining systems follows.

• Geogrid-Reinforced Retaining Walls and Steep Slopes (1H:1V or steeper).
• Geosynthetic Erosion Control and Vegetative Mats.
• Mechanically Stabilized Earth (MSE) Walls .
• Sheet Pile Walls (Cantilever, Braced, or with Tie-Backs).
• Soil Nailing, Soil Anchors and Rock Anchors .
• Post and Panel Walls .
• Rock Cut Slopes .
• Concrete Retaining Walls (Gravity or Cantilever).
• Gabion and Boulder Retaining Walls.
• Coffer Dams.

Of the nearly 80,000 dams listed in the National Dam Inventory, about 10,000 are identified as high-hazard structures, which means their failure could result in loss of life, significant property damage, critical infrastructure disruption, or severe environmental damage. According to the American Society of Civil Engineers (ASCE) 2005 Report Card for America’s Infrastructure, more than 3,500 of the high-hazard dams are unsafe and a staggering $10.1 billion would be needed over the next 12 years to address all of the critical non-federal ones. The Dam Safety and Security Act enacted by Congress in 2002 fosters coordination among the Federal Emergency Management Agency (FEMA) and state dam safety programs. It mandates periodic inspection, maintenance, and monitoring of dams as well as Emergency Action Plans (EAPs) at all levels of government to deal with a potential catastrophe.

Our geotechnical engineers are qualified to inspect and evaluate dams under federal and state guidelines. In this capacity we have assisted owners with code compliance by performing computer-aided dam break and flood analyses, the results of which serve as the basis for an EAP. Past experience with the rehabilitation of earth and concrete dams has covered crest heightening, foundation design for new spillways and fish passageways, and enhanced downstream erosion protection. Most projects demand expertise in geotechnical instrumentation and interpretation of seepage, piping, drawdown, and stability conditions. Our ability to utilize the results of steady-state seepage (flow net analyses) as input to effective stress FEM is especially useful in this regard.

The design and inspection of liner systems for wastewater lagoons and ponds of all types require expertise in geosynthetic materials, drainage problems, and other geotechnical issues. Some factors considered by GeoStructures on past projects to select the optimal liner are end use, geologic setting, water level fluctuations, reactive chemical effluent, uplift, vegetation, and the risk of karst-related dropouts. Regardless of type, however, attention to detail is critical, with anchor trenches, field seaming, curtain drains, and pipe penetrations playing major roles in long-term performance. QA/QC during construction must address the following items.

• Subgrade Preparation.
• Control of Blasting Operations to Prevent Heave.
• Conformance Testing of Geosynthetics (Field and Laboratory).
• Field Seaming .
• Nondestructive and Destructive Seam Testing.
• Patching and Repair of Damaged Sections .
• As-Built Panel Layout .
• Placement and Compaction of Soil Cover.

Legends of disappearing streams and underground lakes and rivers are common in karst regions, where sinkholes seem to appear overnight to swallow a building or close a commuter roadway. Sinkholes are a natural consequence of soil loss into underlying bedrock solution openings that have formed over eons of time. Erosion domes are the most dramatic and potentially damaging. These features form in cohesive soils and progress upward like “bubbles” through incremental roof collapse until they reach the ground surface. Roof collapse occurs when the width of an underground opening exceeds the ability of the overlying material to arch across it. This process is similar to that of mine subsidence. With water as the accelerator of roof collapse, it follows that areas of focused infiltration such as recently cleared construction sites, drainage channels, and unlined stormwater basins are especially vulnerable to sinkholes.

Chemical decomposition of carbonate rocks such as limestone and dolomite is a natural process. Corrosive agents include rainwater made slightly acidic by dissolved carbon dioxide or groundwater containing dissolved hydrogen sulfide gas from the breakdown of organics. Contrary to popular belief, normal fluctuations in pH—natural or artificial—have virtually no effect on this process over the lifespan of a structure even though some building codes reflect this misconception. In humid climates of the eastern United States fracture surface denudation is only 1 to 1-½ in. per 1,000 years. At this rate, it would take at least 100,000 years to form a 12-ft wide slot in the rock and millions of years to create extensive underground caverns!

Building with confidence in karst demands detailed subsurface investigations to identify incipient sinkholes and characterize a site’s unique hydrogeologic factors. Universal tools of intrusive investigation include borings, percussion probes, and test pits. Recognizing that high angle discontinuities are more vulnerable to large openings, geologic mapping of rock exposures on or near a job site for weathering and fracturing can provide insight into the alignment of underground slots in the bedrock. In the absence of visible outcrops and as a complement to geologic mapping, aerial photo stereo pairs can be obtained for many sites. Such photos are examined for fracture traces—recognizable as lineaments of dark ground caused by deep weathering, increased moisture and dense vegetation. Geophysical tools may also be applied to obtain 2-D profiles of the ground and rock between discrete borings. Effective techniques include microgravity, electromagnetic (EM), DC resistivity, and seismic refraction surveys.

Methods of sinkhole repair and ground stabilization vary depending on structural importance, working constraints, soil type, depth to rock, and depthto groundwater. GeoStructures has utilized and refined a cost-effective, shallow bridging remediation technique. In this approach, raveled soils are replaced with a reinforced plug of geosynthetics, riprap, and stone. Deep, high-risk features hampered by shallow groundwater or tight working conditions may require compaction grouting, which is the injection of low slump grout into the ground and rock under high pressure to fill voids and compact raveled soils. Both types of repairs have been successful on numerous private as well as PennDOT and Pennsylvania Turnpike projects.

Depending on structure type, height, sensitivity to settlement, seismic zone, site conditions, and other factors, the cost of a foundation as a percentage of total project cost can vary dramatically. Our goal as geotechnical engineers is to develop technically sound support systems while minimizing costs. Optimum foundation designs do not naturally arise from equations or design charts; they are a product of outstanding engineering judgment developed through years of experience in the design and construction fields.

When multiple foundation types seem equally feasible, selecting the best system for the job can be challenging but also very rewarding. Responsible design optimization requires us to look beyond subsurface investigations and routine cost estimates. Our engineers are skilled at asking the right questions about site grading, construction sequencing, schedule, abilities of local construction forces, and other project-specific variables that could affect design or construction of a foundation.

Innovative yet practical solutions are integrated by GeoStructures into every foundation design and evaluation project. Our experience encompasses all types of support systems and load testing, including: shallow foundations; mat footings; driven, drilled, jetted, bored, auger cast, precast, and cast-in-place piles; and drilled piers or caissons. Our capabilities extend beyond standard services to soil-structure interaction modeling and comprehensive foundation design and inspection.

When it comes to rehabilitation and underpinning of existing foundations, our strength in finite element analysis enables us to accurately model the foundation behavior and establish the most reliable rehabilitation scheme. In coordination with the owner, engineer or architect, we often design the selected rehabilitation system, provide complete drawings and specifications, and monitor its implementation. This gives us significant advantages over proprietary contractors who may tend to utilize one system or another without due evaluation and cost comparison.

Deep room-and-pillar mines have been active in Pennsylvania’s coalfields since the late 1700s. Sinking of the ground surface above the mines occurs as long troughs or local circular potholes. Troughs are caused by the crushing failure of coal pillars or the punching of coal pillars into the underclay (fireclay) of a mine floor. Potholes form when a mine roof collapses and the overburden is less than about 50 ft. Similar to dome sinkholes in karst regions, potholes usually occur suddenly and can cause severe structural damage.

Factors controlling mine subsidence include height of the mined-out coal bed, pillar size, width between pillars, overburden thickness, and rock strength. According to the Ohio Division of Geological Survey, the potential area of subsidence extends beyond the extraction area along a 35° angle of projection, called the angle of draw. The deeper the mine, the larger the area potentially affected by mine subsidence at the surface.

Site investigations and risk assessments start with research of historic mine maps kept in the Department of the Interior’s Office of Surface Mining (OSM). This is followed by a program of deep test borings, geologic mapping, and geophysics to further delineate subsurface openings. Examples of geophysical techniques are borehole tomography and cross-hole seismic surveys. Detailed subsurface investigations enable different levels of risk to be assigned based on various controlling parameters, such as the ratio of overburden to void height. An added comfort level can be gained by using FEM to model underground stresses and deformations due to surface loads and site-specific subsurface factors.

Commonly employed methods for stabilizing the ground above old mines involve compaction grouting—a technique similar to that used to repair karst-related sinkholes. Low slump concrete mixes may be initially injected as a barrier in advance of using less expensive, high slump and low strength cement and fly ash as production grout. The grout fills mine openings in the area of the collapse and also builds columns from the floor of the mine to the ground surface.

Scarce available open land in densely developed metropolitan areas and the inherent challenges posed by undocumented fills, demolition debris or soft floodplain deposits are a few of the driving forces behind recent innovations in soil improvement. With the advent of new technologies, sites ignored in the past can now be developed using economical shallow foundations and conventional slab on grade instead of costly pile or caisson foundations and structural ground floor slabs. Detailed subsurface investigations are critical to the selection and proper use of any soil improvement technology.
Options for large-scale, in-place densification of granular soils include intensive proofrolling, dynamic compaction, and other densification/compaction techniques. Post-construction settlement of soft, saturated silt and clay deposits, on the other hand, can be mitigated through preloading. For marginal sites, a combination of methods may be the best approach. Lightweight fills can also be used to actually offset structural loads and essentially “float” a building. GeoStructures has extensive experience in the design, testing and monitoring of the following soil improvement methods:

• Intensive Proofrolling to Deeply Propagate Compaction Energy.
• Ballast-Stabilized Footing Excavations.
• Compaction and Low Mobility Grouting.
• Deep Dynamic Compaction.
• Vibro-Compaction and Vibro-Replacement.
• Preloading and Sand or Wick Drains.
• Cellular Concrete or Geofoam.
• Lightweight Fill.

The oldest known use of lime as an agent of chemical subgrade stabilization was by the ancient Romans when building the Appian Way in 312 B.C. On modern highway projects, lime has been traditionally utilized as a construction expedience to safeguard clayey subgrade against potential softening due to rain. Such an approach, however, does not account for any of the strengthening effects in design. Our engineers were the first in Pennsylvania to overcome this shortcoming and incorporate the benefits of lime and cement stabilization into the pavement design of a major section of the Pennsylvania Turnpike.

Lime improves the strength of clay by hydration, flocculation and cementation. The first and second mechanisms occur almost immediately upon introducing the lime, while the third is a prolonged effect. Our in-house expertise in lime and cement stabilization covers all aspects of the work from determining the mixture design proportion and assessing the strength gain with time to field implementation and testing. Highlights of key components follow:

• Lime Material Property Testing and Evaluations.
• Laboratory Soil-Lime Mix Design.
• Modulus and Strength Property Characterization.
• Pavement Design Using Lime Stabilized Subbase and Subgrade.
• Construction Specifications.
• Mixing Uniformity and Thickness.
• Mellowing Requirements.
• Roller Types and Energy Ratings.
• Compaction Testing.
• Dynamic Cone Penetrometer (DCP) Testing.
• Clegg Impact Hammer Testing.
• Undisturbed or Field Molding of Stabilized Subgrade.
• Laboratory Curing of Field Samples.
• Unconfined Compressive Strength and Resilient Modulus Testing.

Prior to the emergence of geotechnical engineering as an applied science, engineers, architects, and builders relied to a large extent on nearby edifices when selecting and designing a support system for a structure. Accepting that soil profiles and rock masses present in nature are seldom homogeneous, elastic and isotropic, the potential problems of this approach are obvious. And yet degrees of the above thinking still prevail!

Overcoming biased foundation directives can be demanding but also very rewarding for a geotechnical engineer, and GeoStructures is truly at the forefront of this endeavor. We have utilized innovative foundation systems on numerous projects with difficult subsurface conditions under opposition and local misconceptions.

It is our conviction that every project no matter how large or small can benefit from a thorough subsurface investigation due to its unique set of conditions and influencing geologic factors. We are experienced in the following aspects of site characterization.

• Test Borings and Test Pits.
• Standard Penetration Testing (SPT).
• Cone Penetrometer Testing (CPT).
• Seismic Cone Penetration Testing (SCPT).
• Undisturbed (Shelby) Tube Sampling of Soils.
• Rock Coring.
• Air Rotary (Percussion) Drilling.
• Direct Push or “Geoprobe” Sampling.
• Electromagnetic (EM), Seismic, Ground Penetrating Radar (GPR) & Microgravity Surveys.
• Fracture Tracing and Photogrammetry (Stereo Pairs of Aerial Photos).
• Geologic Mapping.
• Geotechnical Instrumentation.
• Hydrogeologic Studies: Piezometers and Monitoring Wells.
• Laboratory Testing Services.
• Rock Structure Measurements (Strike and Dip of Beds, Joints, Faults, etc.).

Our extensive expertise in soil-structure interaction, constitutive modeling and the geotechnical applications of the finite element method (FEM) enable us to better understand and optimize complex foundations, braced excavations, slopes and retaining systems, embankments, dams and pavements. Yet no amount of modeling and sophisticated analyses can account for missing key subsurface factors. Therefore, before accurately modeling any given project, we place significant emphasis on subsurface site characterization to identify its critical and unique subsurface factors. This is the main distinguishing feature of our work and what truly sets us apart. Our expertise in this area of practice includes:

• Site specific response spectra and soil dynamic analysis.
• Braced excavations.
• Pavement stress analysis and mechanistic design.
• Steady state seepage and transient flow analysis.
• Groundwater modeling and contaminant transport.
• Machine foundations.
• Lateral capacity of piles and caissons.
• Stress deformation behavior of foundation systems.
• Soft and hard ground tunneling.

Loma Prieta 1989 USGS Gilroy #1 Station	Ground Acceleration Spectrum

Depending on structure type, height, sensitivity to settlement, seismic zone, site conditions, and other factors, the cost of a foundation as a percentage of total project cost can vary dramatically. Our goal as geotechnical engineers is to develop technically sound support systems while minimizing costs. Optimum foundation designs do not naturally arise from equations or design charts; they are a product of outstanding engineering judgment developed through years of experience in the design and construction fields.

When multiple foundation types seem equally feasible, selecting the best system for the job can be challenging but also very rewarding. Responsible design optimization requires us to look beyond subsurface investigations and routine cost estimates. Our engineers are skilled at asking the right questions about site grading, construction sequencing, schedule, abilities of local construction forces, and other project-specific variables that could affect design or construction of a foundation.

Innovative yet practical solutions are integrated by GeoStructures into every foundation design and evaluation project. Our experience encompasses all types of support systems and load testing, including: shallow foundations; mat footings; driven, drilled, jetted, bored, auger cast, precast, and cast-in-place piles; and drilled piers or caissons. Our capabilities extend beyond standard services to soil-structure interaction modeling and comprehensive foundation design and inspection.

When it comes to rehabilitation and underpinning of existing foundations, our strength in finite element analysis enables us to accurately model the foundation behavior and establish the most reliable rehabilitation scheme. In coordination with the owner, engineer or architect, we often design the selected rehabilitation system, provide complete drawings and specifications, and monitor its implementation. This gives us significant advantages over proprietary contractors who may tend to utilize one system or another without due evaluation and cost comparison.

Construction monitoring and materials testing are the bridge between design and a safe, economical, high quality, completed project. GeoStructures provides QA/QC and construction-related services to owners, architects, engineers, design/build contractors, general contractors, developers, and state and federal highway and transportation agencies. All of our field personnel are experienced and certified engineers or engineering geologists. Our QA/QC services cover:

• Shallow Foundations.
• Subgrade Proofrolling.
• Fill Compaction Testing.
• Plate Load Testing of Subgrade.
• Asphalt and Rigid Pavements.
• Drilled Shafts (Caissons).
• Pile Driving and Load Testing (Static and Dynamic).
• Cast in Place Concrete.
• Masonry, Grout, Mortar and Reinforcement.
• Precast Concrete Connections.
• Structural Steel.
• Slab Flatness and Levelness (F-number).
• Vibration and Noise Monitoring.
• Subgrade Lime and Cement Stabilization.
• Geomembrane Liner Installation and Testing.

As long, narrow, nearly two-dimensional elements, highways and other transportation corridors traverse a variety of terrain, topography, geology, and cultural settings. Among public works projects, transportation-related infrastructure ones involve, perhaps, the greatest diversity of structures.

It is not uncommon for a single interstate segment measuring only a few miles to have bridges, tunnels, viaducts, overpasses, underpasses, deep cuts, high fill embankments, natural soil and rock slopes, steep reinforced slopes, earth retaining systems, shoring, and buried culverts in either rural or urban settings. In fact, most of the professional services we offer at GeoStructures can be covered under this category.

Our engineers possess the breadth of experience and qualifications to handle the many geotechnical and foundation related challenges posed by bridge and highway projects, and we have a proven record with PennDOT, DelDOT, NJDOT, SEPTA, and the Pennsylvania Turnpike Commission. Some of our most innovative engineering and design work have been incorporated into major transportation projects.

Without exception, today’s major highways incorporate some form of concrete (rigid) or asphalt (flexible) pavements. While Roman engineers are generally credited with the first true concrete more than 2,000 years ago, hot mix asphalt technology advanced gradually, with landmark innovations and widespread use occurring over the past 150 years or so. GeoStructures provides complete pavement-related services, including investigation, design, rehabilitation, and evaluation of both rigid and flexible pavements in accordance with AASHTO and state DOT standards. A list of our pavement-related services follows.

• California Bearing Ratio (CBR) and Resilient Modulus (M R) Testing.
• Clegg Impact Hammer (CIH) and Dynamic Cone Penetrometer (DCP) Testing .
• Condition Surveys and Assessment of Remaining Life.
• Coring, Test Borings, and Subgrade Sampling .
• Finite Element Analysis of Pavement Structures and Subgrade.
• Extraction Testing of Pavement Cores.
• Falling Weight Deflectometer (FWD) .
• Geotextiles, Geomebrances, Geogrid, and Steel Mesh Applications.
• Lime and Cement Stabilization of Subbase and Subgrade.
• Rehabilitation Alternatives and Life Cycle Cost Analysis.
• Reflective Cracking Mitigation.
• Laboratory and In-Situ Pavement Permeability Testing.
• Frost Behavior of Subbase and Subgrade Materials.
• Forensic Studies of Premature Pavement Failures.

According to the National Landslide Hazards Program (NLHP) administered by the USGS, landslides constitute a major geologic hazard because they are widespread and can be quite severe; they occur in all 50 states and U.S. territories and cause an average of $1 to 2 billion in damages each year. GeoStructures is experienced in the design, evaluation and rehabilitation of a full range of earth/rock slopes and retaining systems for transportation facilities, commercial sites, and residential developments. In addition to competency in traditional limit-equilibrium analysis, our strength in soil-structure interaction modeling and use of FEM enables us to gain a deeper understanding of complicated slopes and earth retaining systems.
In the area of retaining systems, our engineers were among the first in Pennsylvania (late 1980s) to design geogrid-reinforced retaining walls, structures commonly referred to today as mechanically stabilized earth (MSE) walls or segmental retaining walls (SRW). A summary of our capabilities in the design of slope and retaining systems follows.

• Geogrid-Reinforced Retaining Walls and Steep Slopes (1H:1V or steeper).
• Geosynthetic Erosion Control and Vegetative Mats.
• Mechanically Stabilized Earth (MSE) Walls .
• Sheet Pile Walls (Cantilever, Braced, or with Tie-Backs).
• Soil Nailing, Soil Anchors and Rock Anchors .
• Post and Panel Walls .
• Rock Cut Slopes .
• Concrete Retaining Walls (Gravity or Cantilever).
• Gabion and Boulder Retaining Walls.
• Coffer Dams.

Of the nearly 80,000 dams listed in the National Dam Inventory, about 10,000 are identified as high-hazard structures, which means their failure could result in loss of life, significant property damage, critical infrastructure disruption, or severe environmental damage. According to the American Society of Civil Engineers (ASCE) 2005 Report Card for America’s Infrastructure, more than 3,500 of the high-hazard dams are unsafe and a staggering $10.1 billion would be needed over the next 12 years to address all of the critical non-federal ones. The Dam Safety and Security Act enacted by Congress in 2002 fosters coordination among the Federal Emergency Management Agency (FEMA) and state dam safety programs. It mandates periodic inspection, maintenance, and monitoring of dams as well as Emergency Action Plans (EAPs) at all levels of government to deal with a potential catastrophe.

Our geotechnical engineers are qualified to inspect and evaluate dams under federal and state guidelines. In this capacity we have assisted owners with code compliance by performing computer-aided dam break and flood analyses, the results of which serve as the basis for an EAP. Past experience with the rehabilitation of earth and concrete dams has covered crest heightening, foundation design for new spillways and fish passageways, and enhanced downstream erosion protection. Most projects demand expertise in geotechnical instrumentation and interpretation of seepage, piping, drawdown, and stability conditions. Our ability to utilize the results of steady-state seepage (flow net analyses) as input to effective stress FEM is especially useful in this regard.

GeoStructures is actively involved in research and advancement of the state-of the-art and state-of-practice geotechnical engineering technology through: participation in TRB and ASCE technical committees; publication of innovative work; and peer reviews of journal and conference research papers. Our engineers have also played key roles including that of principal investigator for small business innovative research (SBIR) projects to investigate the potential use of waste byproducts for structural fill in highway applications. In addition, our chief engineer serves as an adjunct professor of geotechnical engineering at Drexel University where he teaches an advanced graduate level course on constitutive modeling in geomechanics, as well as development and updating of the course material.

Prior to the emergence of geotechnical engineering as an applied science, engineers, architects, and builders relied to a large extent on nearby edifices when selecting and designing a support system for a structure. Accepting that soil profiles and rock masses present in nature are seldom homogeneous, elastic and isotropic, the potential problems of this approach are obvious. And yet degrees of the above thinking still prevail!

Overcoming biased foundation directives can be demanding but also very rewarding for a geotechnical engineer, and GeoStructures is truly at the forefront of this endeavor. We have utilized innovative foundation systems on numerous projects with difficult subsurface conditions under opposition and local misconceptions.

It is our conviction that every project no matter how large or small can benefit from a thorough subsurface investigation due to its unique set of conditions and influencing geologic factors. We are experienced in the following aspects of site characterization.

• Test Borings and Test Pits.
• Standard Penetration Testing (SPT).
• Cone Penetrometer Testing (CPT).
• Seismic Cone Penetration Testing (SCPT).
• Undisturbed (Shelby) Tube Sampling of Soils.
• Rock Coring.
• Air Rotary (Percussion) Drilling.
• Direct Push or “Geoprobe” Sampling.
• Electromagnetic (EM), Seismic, Ground Penetrating Radar (GPR) & Microgravity Surveys.
• Fracture Tracing and Photogrammetry (Stereo Pairs of Aerial Photos).
• Geologic Mapping.
• Geotechnical Instrumentation.
• Hydrogeologic Studies: Piezometers and Monitoring Wells.
• Laboratory Testing Services.
• Rock Structure Measurements (Strike and Dip of Beds, Joints, Faults, etc.).

Our extensive expertise in soil-structure interaction, constitutive modeling and the geotechnical applications of the finite element method (FEM) enable us to better understand and optimize complex foundations, braced excavations, slopes and retaining systems, embankments, dams and pavements. Yet no amount of modeling and sophisticated analyses can account for missing key subsurface factors. Therefore, before accurately modeling any given project, we place significant emphasis on subsurface site characterization to identify its critical and unique subsurface factors. This is the main distinguishing feature of our work and what truly sets us apart. Our expertise in this area of practice includes:

• Site specific response spectra and soil dynamic analysis.
• Braced excavations.
• Pavement stress analysis and mechanistic design.
• Steady state seepage and transient flow analysis.
• Groundwater modeling and contaminant transport.
• Machine foundations.
• Lateral capacity of piles and caissons.
• Stress deformation behavior of foundation systems.
• Soft and hard ground tunneling.

Loma Prieta 1989 USGS Gilroy #1 Station	Ground Acceleration Spectrum

Depending on structure type, height, sensitivity to settlement, seismic zone, site conditions, and other factors, the cost of a foundation as a percentage of total project cost can vary dramatically. Our goal as geotechnical engineers is to develop technically sound support systems while minimizing costs. Optimum foundation designs do not naturally arise from equations or design charts; they are a product of outstanding engineering judgment developed through years of experience in the design and construction fields.

When multiple foundation types seem equally feasible, selecting the best system for the job can be challenging but also very rewarding. Responsible design optimization requires us to look beyond subsurface investigations and routine cost estimates. Our engineers are skilled at asking the right questions about site grading, construction sequencing, schedule, abilities of local construction forces, and other project-specific variables that could affect design or construction of a foundation.

Innovative yet practical solutions are integrated by GeoStructures into every foundation design and evaluation project. Our experience encompasses all types of support systems and load testing, including: shallow foundations; mat footings; driven, drilled, jetted, bored, auger cast, precast, and cast-in-place piles; and drilled piers or caissons. Our capabilities extend beyond standard services to soil-structure interaction modeling and comprehensive foundation design and inspection.

When it comes to rehabilitation and underpinning of existing foundations, our strength in finite element analysis enables us to accurately model the foundation behavior and establish the most reliable rehabilitation scheme. In coordination with the owner, engineer or architect, we often design the selected rehabilitation system, provide complete drawings and specifications, and monitor its implementation. This gives us significant advantages over proprietary contractors who may tend to utilize one system or another without due evaluation and cost comparison.

Construction monitoring and materials testing are the bridge between design and a safe, economical, high quality, completed project. GeoStructures provides QA/QC and construction-related services to owners, architects, engineers, design/build contractors, general contractors, developers, and state and federal highway and transportation agencies. All of our field personnel are experienced and certified engineers or engineering geologists. Our QA/QC services cover:

• Shallow Foundations.
• Subgrade Proofrolling.
• Fill Compaction Testing.
• Plate Load Testing of Subgrade.
• Asphalt and Rigid Pavements.
• Drilled Shafts (Caissons).
• Pile Driving and Load Testing (Static and Dynamic).
• Cast in Place Concrete.
• Masonry, Grout, Mortar and Reinforcement.
• Precast Concrete Connections.
• Structural Steel.
• Slab Flatness and Levelness (F-number).
• Vibration and Noise Monitoring.
• Subgrade Lime and Cement Stabilization.
• Geomembrane Liner Installation and Testing.

As long, narrow, nearly two-dimensional elements, highways and other transportation corridors traverse a variety of terrain, topography, geology, and cultural settings. Among public works projects, transportation-related infrastructure ones involve, perhaps, the greatest diversity of structures.

It is not uncommon for a single interstate segment measuring only a few miles to have bridges, tunnels, viaducts, overpasses, underpasses, deep cuts, high fill embankments, natural soil and rock slopes, steep reinforced slopes, earth retaining systems, shoring, and buried culverts in either rural or urban settings. In fact, most of the professional services we offer at GeoStructures can be covered under this category.

Our engineers possess the breadth of experience and qualifications to handle the many geotechnical and foundation related challenges posed by bridge and highway projects, and we have a proven record with PennDOT, DelDOT, NJDOT, SEPTA, and the Pennsylvania Turnpike Commission. Some of our most innovative engineering and design work have been incorporated into major transportation projects.

Without exception, today’s major highways incorporate some form of concrete (rigid) or asphalt (flexible) pavements. While Roman engineers are generally credited with the first true concrete more than 2,000 years ago, hot mix asphalt technology advanced gradually, with landmark innovations and widespread use occurring over the past 150 years or so. GeoStructures provides complete pavement-related services, including investigation, design, rehabilitation, and evaluation of both rigid and flexible pavements in accordance with AASHTO and state DOT standards. A list of our pavement-related services follows.

• California Bearing Ratio (CBR) and Resilient Modulus (M R) Testing.
• Clegg Impact Hammer (CIH) and Dynamic Cone Penetrometer (DCP) Testing .
• Condition Surveys and Assessment of Remaining Life.
• Coring, Test Borings, and Subgrade Sampling .
• Finite Element Analysis of Pavement Structures and Subgrade.
• Extraction Testing of Pavement Cores.
• Falling Weight Deflectometer (FWD) .
• Geotextiles, Geomebrances, Geogrid, and Steel Mesh Applications.
• Lime and Cement Stabilization of Subbase and Subgrade.
• Rehabilitation Alternatives and Life Cycle Cost Analysis.
• Reflective Cracking Mitigation.
• Laboratory and In-Situ Pavement Permeability Testing.
• Frost Behavior of Subbase and Subgrade Materials.
• Forensic Studies of Premature Pavement Failures.