IFCEE 2018: Recent Developments in Geotechnical Engineering Practice

Progress on the $750M lock project on the Monongahela River was derailed by discovery of large anomalies in the 6.5–7-ft diameter drilled shafts of the new river wall foundation. The anomalies were located 45 to 50’ below the top of the wall at the critical shaft-to-wall interface, and ranged in thickness from several inches to 2-plus feet. A specialty team, comprised of representatives from the contractor, the government, and structural design consultants, was formed to evaluate the extent of the problem and the impact on the new lock wall. With no standard method in place, the government took the lead to develop acceptance criteria for the repairs while the contractor took the lead to identify the repair means and methods. The government developed a detailed quality control plan to capture and document all of the repair data and to approve each shaft repair in a timely manner. This paper provides an overview of the anomalies encountered and the need for repairs; discusses the details of the repair plan; and provides details on the unique quality control measures employed to verify the repairs. By developing and adhering to a detailed quality control plan, the structural integrity of all of the shafts was successfully restored.

A seven-story concrete-framed office building and a three-story concrete-framed parking garage were built on the footprint of several abandoned coal mines. The mines were excavated using the room-and-pillar method, initially leaving pillars of coal in place to support the mine roof. During retreat mining, some of the pillars were removed and replaced by temporary support measures. Based on these ground conditions permanently cased drilled shafts were chosen to support both structures. The drilled shafts were founded in the bedrock below the underground voids and coal seams at the mine levels and are cased with a permanent liner through the voids and overburden soils. BAUER Foundations Corp. (BFC) performed probe drilling at each of the drilled shaft locations in order to confirm the existence and location of the void. Following this operation, BFC installed 126 drilled shafts with diameters of 36, 42, and 54 in. and depths up to 80 ft. BFC successfully managed the excavation of the unweathered sandstone above and below the mine levels. Based on the encountered conditions of the rocks above the mine, BFC changed the initially planned method and used only a temporary starter casing and drilled the remainder of the rock above the mine level without additional support. Subsequently, the liner was seated and sealed into the bedrock and the shaft was drilled to final depth. The vast majority of the shafts were dry, so that it was possible to pour the concrete using the free-fall method. The paper focuses on the description of the experiences made as well as on the lessons learned during both the probe drilling, drilling through hard sandstone, voids and collapse zones, and concreting of the drilled shafts.

A case history is presented of drilled shaft foundations found to have anomalous concrete and, in some cases, structural deficiencies. The process that was implemented in response to the anomalies and deficiencies provides an illustrative example of how post-installation problems can be addressed effectively in order to ensure that foundation design criteria are satisfied. The project involved drilled shafts for the goethals bridge replacement (GBR), a dual-span cable-stayed bridge crossing the Arthur Kill between Elizabeth, NJ and Staten Island, NY supported on over 200 rock-socketed drilled shaft foundations. The drilled shafts that are the subject of this paper are located in a section of the Eastbound bridge starting at the west abutment (NJ side) and including the next four piers east of the abutment. All of the subject shafts are 4.5-ft diameter with permanent casing to rock and 4-ft diameter rock sockets. Following construction, cross-hole sonic logging (CSL), and tomography (CT) identified anomalous readings in 16 of the 23 shafts. All of the anomalies were located in the rock-socketed portion of the shafts near the tip. Based on the severity of the anomalies and evaluation of geotechnical and structural demands, two of the anomalous shafts were accepted without additional investigation. The remaining 14 shafts were investigated by concrete coring. Based on the coring results and further analyses, seven additional shafts were accepted without further action. The remaining seven shafts were repaired by using hydro-demolition to remove defective concrete followed by replacement with grout. This paper describes the process used to characterize and evaluate the nature of potential defects in each shaft and how that formed a basis for decisions on whether each shaft was accepted, selected for further investigation, or designated for repair. The repair process, including quality control, and quality assurance procedures, is presented in detail. Lessons learned and their application to future projects are presented.

The case history discusses development of a 14 story, 675,000-square-foot (62,700 square meter) building supported by over 350 hollow-stem, cast-in-place friction piles with an average depth of 90 ft (27 m) at a former Navy Yard dry dock. The chosen pile type was the result of a value-engineering effort proposed by the contractor and replaced traditional caisson piles originally proposed during design. Hollow-stem, cast-in-place piles are well suited for conditions where soil is easily displaced because the pile type tends to have an increased production rate. However, difficulties during construction can quickly arise in more challenging ground conditions. In this paper, the difficult subsurface conditions and below-grade obstructions are explained, as well as the pile installation method and modifications resulting from challenges that arose while constructing and testing the piles. We provide details about the comprehensive axial compression load-test program. Finally, we provide lessons learned and recommendations for future use of hollow-stem, cast-in-place piles under complex site, and subsurface conditions.

The project discussed in this paper consisted of replacing two 12-span interstate bridges with two 4-span bridges in an area with complex subsurface conditions. A preliminary geotechnical investigation encountered a thick cobble/boulder layer in two of three widely-spaced borings at depths as shallow as 20 ft below grade. Driven piles and drilled shafts were initially evaluated as foundation alternatives. A subsequent geotechnical investigation encountered the relatively shallow cobble/boulder layer in all borings at depths from 20 to 30 ft below grade. Driven piles were evaluated as a cost savings alternative, and preliminary geotechnical analyses determined the allowable lateral and uplift capacities could be borderline or even insufficient if piles were to refuse on the boulder layer. Because of the extensive foundations required for the two bridges, and the potential cost savings if piles could be utilized, a pile testing program was performed during design to determine the axial, lateral, and uplift capacity of shallow piles. Five test piles were driven to refusal on the cobble/boulder layer at two bent locations, including H-piles and pipe piles. A shape accel array (SAA) full-depth inclinometer was installed in one of the pipe piles to determine the full-depth movement of the pile during lateral loading. Based on the test results, it was determined that shallow pipe piles could be utilized as the foundation type. More precise soil properties were backcalculated from the pile testing program which allowed the geotechnical and structural engineers to optimize the pile layout and depth during design. The total number of piles driven during construction was 372. Prior to construction, the total estimated pile length for the two structures was 13,020 lineal feet, and actual pile length used was 13,170 lineal feet, or within 1% of estimated. Only four welds were required on the 372 piles and no construction delays were encountered during pile driving. Estimated cost savings of using piles versus drilled shafts for this project was $2M to $3M.

PND Engineers, Inc. (PND) has performed extensive testing on their trademarked SPIN FIN^™ piles over the last 30 years to better understand and utilize these piles. SPIN FIN piles are most commonly used to provide geotechnical resistance due to large tensile and compressive forces, but are unique due to the disturbance of the soil during the driving process. The ultimate tensile capacity is derived from the pile’s skin friction and uplift capacity of the finned portion of the pile. This paper highlights two projects in which the authors performed high strain dynamic testing (HST) on SPIN FIN piles. The HST testing provided estimates of the ultimate tensile capacity with a high degree of accuracy, including one project with restrikes in soft marine sediments to determine the soil “setup.” The purpose of this paper is to present background on the project geotechnical conditions, SPIN FIN pile design challenges, construction pile driving data collection, and signal matching of reduced data.

Modern deep foundation designers regularly use the wave equation and high strain dynamic testing (HST) during installation. Since the mid-1900s, many projects have used and continue to rely solely on the wave equation to confirm driven pile capacity. The added benefit from HST is the ability to not only assess for pile capacity and pile integrity, but also to monitor the energy transfer from the hammer to the pile. The transfer of energy is a fundamental input to the wave equation. The energy transfer is important during pile installation, though many times it is not fully recognized how much the input varies or to what extent it influences the results. This paper performs a desktop study and then highlights several driven pile projects in which HST measurements indicated lower energy transfer from the impact hammer than what would have been predicted by the wave equation. The energy transfer data is compared to projects that hypothetically only performed the wave equation with no confirmation of energy transfer to evaluate the resulting factors of safety.

The project consists of a high-rise building supported on driven piles. Design objectives included determining the highest maximum long-term capacity which could be reasonably obtained from a drivability perspective, using readily available equipment. A pre-production test program was performed on 16-in. -diameter (406-mm-diameter) ASTM 252, Grade 3 (45 ksi and 310 MPa) steel pipe piles, having a wall thickness of 0.50 in. (13 mm). Based on evidenced capacities, including long-term set-up, a maximum allowable pile load of 600 kips (2,670 kN) was used on the project. The cost-effectiveness of the test program was evaluated by comparing the cost of a design using 600-kip allowable load piles to alternative designs using the same pile section, but assuming that various lesser testing scenarios had been performed, warranting higher safety factors. Six complete alternative foundation designs were performed for these lower allowable pile loads. Costs associated with the piles (based on production-pile driving behavior), concrete caps and mat, and construction-control methods were estimated for the redesigns. Foundation costs were evaluated for piles designed both with and without the benefit of capacity contribution from set-up. Cost differences among the various construction-control methods were determined in terms of total cost, and support cost. Pile-driving schedule impacts associated with the six alternative allowable loads were also estimated. Additional savings that resulted from applying test-program results to production piles which were damaged or terminated short were quantified.

The Bonner bridge replacement project is a 2.7 mi bridge over the Oregon Inlet on the Outer Banks of North Carolina. The new bridge will replace the existing Bonner bridge built in 1963. The existing bridge has experienced multiple storm, scour, and ship impact events which have resulted in numerous bridge closures and underpinning of some foundation piles. The new bridge foundations consist of three pile types: 36-in. square precast, pre-stressed concrete with a 21-in. diameter void, 54-in. diameter cylinder piles, and 20-in. square precast, pre-stressed concrete. This paper will describe the methods selected for production pile installation and the successes/problems encountered with the planned methods. Results from the static load testing and PDA testing results will also be discussed in detail.

Pile driving in soft clays can cause lateral displacements due to undrained soil deformation that can affect adjacent structures. This paper describes observations, measurements, and analysis of lateral soil movements manifested during a large pile driving project using “displacement” piles in soft clays in East Baton Rouge, LA. The piles were driven in close proximity to a newly constructed, pile-supported, concrete cantilever retaining wall along the edge of the property. During the initial phase of the pile driving, lateral movements of up to 28 cm (11 in.) and outward rotations of up to 0.8° were measured in the retaining wall. Due to concerns about potential additional lateral soil movement, the subsequent phase of pile driving was monitored with vibration monitoring equipment, piezometers, and inclinometers in the ground between the pile driving and the retaining wall. The authors analyzed the raw monitoring data and compared them with predictions of lateral movements and pore pressures using cavity expansion theory. The measured data and analysis presented in this paper show that lateral movements of the pile-supported retaining wall were caused primarily by pile driving and that pile driving, even at distances greater than 50 times the pile diameter, can have a measurable cumulative effect on lateral soil movements and should not be summarily discounted.

Replacement foundation installations for three of the six bridge locations along the Saw Mill River Parkway included under a New York State Department of Transportation (NYSDOT) design/build contract presented significant challenges for the project team. At two of the locations, the existing columns supporting the traffic deck were founded in the middle of a river directly beneath historic stone arched bridges carrying local traffic. During a storm event, tree limbs and other debris would catch against the columns, forming dam structures sufficient to cause local community flooding. Micropiles were selected to replace the river bearing columns and abutments and also to provide lateral restraint for support of the above roadway and embankment. Design and installation of the micropiles at these locations demanded an innovative approach to technical challenges. This paper will discuss the solutions to the challenges presented at all three locations, the technical success of which was a direct result of close collaboration and cooperation by all members of the design/build team throughout the work.

Micropiles can be used as energy collectors simultaneously when functioning as load bearing structures. This possibility has become more popular recently as Finland has set the regulation for all the new public buildings to meet the zero energy level by 2020. The focus in this study is on energy micropiles which provide thermal energy to be stored to undisturbed soil under the building. The soil works as an energy storage medium. In this study, energy simulations were carried out during the planning process. The energy simulations specified the amount and period of the heating and cooling energy consumptions in the buildings. According to the energy simulation steel micropiles can be used efficiently for storing energy and as a source of energy in Finnish conditions. At the commercial building temperatures used in simulation was not found to have significant geotechnical influences. However, no long term modelling of the current energy utilization technique has been carried out. Hence it is essential to model the long term thermal behavior of clay for economic, geotechnical, and environmental reasons.

The paper describes the design principles, adopted technologies, and performance controls related to two main geotechnical engineering solutions provided within the scope of the Galataport project, in Istanbul, Turkey. The first scheme is the one applied to the new quay of Salıpazarı, which is a combination of retaining structure and ground improvement, formed by a combi-wall, a reinforced concrete diaphragm wall and a soil improvement by deep soil mixing (Turbojet). The second is an innovative solution employed for the deep basement excavation in Karaköy, formed by a combination of seepage control, ground improvement, and load bearing elements, executed with double-fluid jet grouting, pseudo-elliptical jet grouting, and permanent micropiles, respectively. The paper highlights the importance of employing cutting-edge technologies within the foundation engineering field and state-of-the-art electronic control devices, in parallel with the essential human expertise, in order to obtain the desired results in this high profile project.

When a developer in New York city faces zoning constraints, often few options are available to maximize a building’s footprint. Developers know, however, that historical zoning codes that had been applied to an existing building in can be applied to new construction if part of the existing building is retained. In addition to being able to use an old zoning code, developers face few, if any, imposed zoning constraints on new multilevel deep cellars. Because of these zoning allowances, retaining parts of a building and “going deep” have become a preferred option to maximize space. But the work may be difficult. This paper discusses partial demolition of a 10-story building and construction of a 38-story addition with excavation and support on hard bedrock for two new below-grade subcellars extending 32 ft (9.7 m) below an existing cellar. The paper will also detail how three components of construction—demolition bracing in conjunction with reusing parts of the existing building, underpinning and excavation support, and the cellar slabs of the new building—were used to support the excavation and allow for lot-line construction of the new below-grade levels and support of adjacent buildings and a subway tunnel. Excavation of the hard bedrock required in-depth knowledge of its geophysical conditions. Borehole geophysical logging before construction and geologic mapping during construction were performed to obtain and correlate data on the elevation and quality of the bedrock, and on the discontinuities within the rock for designing the underpinning and excavation support.

It is common knowledge among geotechnical engineers and contractors that most of the uncertainty in the design, price, and schedule of sheeting, shoring, and underpinning projects lies in the ground conditions. Delays and additional costs can accrue quickly when the conditions underground change or if they are ill-defined. Common challenges include soft, loose or wet ground, rock, ground water and dewatering, adjacent construction, undercutting, unapproved modifications, system stiffness/deflection, and cantilevering. Combine any of these with insufficient investigations and poor communication and the project is heading for trouble. As these common challenges are not new, it is troubling that many engineers do not recognize, understand, or communicate these issues to owners and developers. Failing to learn from old lessons will only lead to more problems. Challenges encountered on sheeting, shoring, and underpinning projects around the National Capital Region are highlighted and presented through a collection of case histories.

Construction of a new emergency vent plant is required as part of the metropolitan transit authority (MTA) New York city transit (NYCT) ongoing upgrade of the subway ventilation system. Secant piles installed to top of bedrock at 30.5–36.6-m (100–120-ft) below ground surface had originally been suggested for both excavation support and groundwater control. However, given the presence of dense, bouldery glacial till from approximately 7.6-m (25-ft) below ground surface, which would make drilling to full depth extremely difficult and costly, alternative methods of groundwater control below the structural requirement of the support of excavation were designed and implemented. As a result, a support of excavation (SOE) and groundwater control system consisting of secant piles installed to the minimum required depth for a stable excavation and a permeation grout curtain wall from the bottom of the secant piles down to the bedrock was implemented. This paper discusses the design and construction of alternative SOE methods implemented by the project team, including an in-depth review of the grouting approach selected.

In order to remodel an existing beach resort on the Gulf of Mexico, an existing three story structure, founded on stepped tapered piles, was to be replaced by a 10-story building with service rooms on a daylight basement level, conference rooms on the next levels, and up-scale hotel rooms on the upper levels. The new building was founded on augered-cast-in-place (ACIP) piles. The pile caps and the basement required excavations between 9 and 15 ft (3–5 m) below ground surface. BAUER Foundations Corp. (BFC) successfully used cutter soil mixing (CSM) to install the support of excavation walls. This technique allowed for the adjustment of the wall alignment during execution in order to avoid existing and new piles and other underground obstructions. Nearly 1,600 – 16-in. (400 mm diameter) ACIP piles were installed to an average depth of 71.5 ft (22 m) below the ground surface (BGS) by BFC to support the new hotel structure. Initial grout overages in piles were excessively high and ground stability issues were encountered in some pile locations. By identifying specific areas of concern BFC was able to modify the approach to ACIP installation, effectively mitigating the ongoing risks, and successfully completed the project.

Mechanically stabilized earth (MSE) walls are the most popular type of fill earth retaining structure in the U.S., and arguably in the world. Despite their popularity, public and private owners who have a large number of walls among their infrastructure assets are facing a dilemma. For decades, bridges, pavements, and buildings have been the primary asset groups on the receiving end of available resources (maintenance and preservation tactics in the forms of time and money). This has left many owners and agencies with a large inventory of aging retaining walls that received little to no attention since original construction. As some owners experience their first serviceability issues on a wall or select number of walls, there has been a growing level of attention drawn to the current condition and remaining service life of their retaining structure inventory. Implementation of a well-planned, cost effective, and efficient asset management program, tailored to permanent retaining walls will be a vital tool to address aging infrastructure. This paper addresses the planning and implementation components of an asset management program for permanent MSE structures. Although the paper specifically focuses on MSE walls, many aspects and factors of the program also apply to other types of cut and fill retaining structures.

During the 1998 El Niño rains, a landslide damaged a 1.5:1 (horizontal to vertical ratio) fill slope approximately 34 m (110-ft) in height that was graded around 1960. The slope was built in an urban neighborhood using low strength compacted fill derived mostly from the local diatomaceous bedrock. The slope had previously experienced several deep failures, which had been locally repaired by removal and recompaction, only to fail again. By 2003, the landslide had moved significantly and there were significant concerns about the safety of neighboring homes. This article describes: (1) the design and implementation of a long term repair to stabilize the landslide using a buttress, two rows of drilled shafts, and tiebacks; (2) the conventional slope stability and numerical modeling analyses used to determine the critical mode of failure for design; (3) the implementation of the landslide stabilization; and most importantly (4) how combining different structural elements resulted in an unanticipated critical failure mode.

This case study describes failure of an interstate connecting-ramp embankment during construction and investigates performance of the prefabricated vertical drains (PVDs) installed to accelerate consolidation of the weak embankment foundation soils. The weak, fine-grained foundation soil experienced less drainage, and thus less consolidation and strength gain, than expected via the PVDs because of an overestimate of the design horizontal coefficient of consolidation. The inverse analyses show the failure was caused by lower than expected shear strength of the foundation soils and an over estimate of the compacted embankment shear strength. As a result, recommendations to estimate horizontal consolidation properties for PVD design and embankment shear strength parameters or future projects are presented.

A medium and a high plasticity clay were selected to construct temporary embankments (one each on two sides of a river) to support a critical load during construction. Due to schedule, cost, and material availability issues, the embankments in the river were to be constructed out of fine-grained clayey soils, rather than a more conventional construction method using granular and rockfill materials. This paper will not discuss the construction aspects specifically, but will focus on the original clay berm design and the following quality control measures to ensure fit for purpose design. The design was carried out by an experienced subcontractor with local knowledge of clay berm construction and material properties. This paper presents the testing performed before construction to predict compacted strengths and perform magnitude and rate of consolidation. Post construction data are then used to compare the predicted and observed results.

The Chagrin River Valley in Northeastern Ohio follows a generally North-South alignment passing through Portage, Geauga, Eastern Cuyahoga, and Western Lake Counties to its termination at Lake Erie. Steep bluffs of Devonian age rock capped with up to tens of feet of till overburden are exposed in many parts of the river valley. The riverbed generally consists of shale. Overburden consists of silty and clayey Pleistocene age till, and lacustrine sediment. The river and its tributaries have carved an extensive network of ravines into the overburden. Slopes in the till tend to be very steep and those in the lacustrine are relatively gentle with many 25% slopes actively failing. A slope failure in the early 1990s risked damage to a large privately-owned structure. The cost of remedial measures was much greater than what most communities and owners could manage. This prompted that community to enact a slope protective ordinance. Other towns and villages quickly followed suit. The stated purpose and justification for these ordinances is to protect public safety, property, and the environment. Various methods are used to define protected areas which are essentially “no build zones” on parcels with steep slopes. As this case study illustrates, sloping sites are too varied and conditions that control slope stability are too complex to be addressed by including a few generic requirements in municipal ordinances. Such ordinances understandably avoid codifying minimum factors of safety, what is required to properly evaluate any sloping site, or dictating what is required for a proper geotechnical evaluation. Whether these ordinances are successful in achieving their goal depends on enforcement and the skill and experience of those tasked with complying with the provisions of the ordinances.

In 2011, Omaha, NE, which is located along the Missouri River, experienced a substantial flood event. Two years later, in the spring of 2013, after the river reached a 5-year low, the riverbank adjacent to the Missouri River wastewater treatment plant (MRWWTP) experienced substantial movement due to slope failure. To protect existing and planned infrastructure at the MRWWTP, CH2M designed a stabilization program, with panels of dry-method deep soil mixing, for 1,730 linear feet of the western bank of the Missouri River. Supplementary soil explorations prior to the start of production discovered unexpected conditions in the form of subsurface obstructions. Soil mixing operations further uncovered the extent of the unknown obstructions. Modification of the installation procedures was required to remove substantial obstructions and advance soil mix panels to the design depths. An unanticipated slide event also occurred during soil mixing installation, in an area that was largely completed, allowing for observation of the successful performance of the ground improvement design and installation.

The City of Austin, TX retained Geosyntec to stabilize approximately 300 linear feet (90 m) of eroding stream bank along lower buttermilk creek to protect a threatened multi-family structure and to rehabilitate and restore riparian habitat along adjacent portions of the stream channel. An innovative creek bank stabilization system was designed and constructed on an expedited schedule to protect the threatened infrastructure. Geosyntec designed a drilled soldier pile and concrete lagging retaining wall for creek bank stabilization, which was combined with limestone block facing and geogrid-reinforced vegetated soil slopes to retain a natural aesthetic. The project team used a variety of analysis methods to optimize the stabilization system design, which needed to be structurally robust, completed in an expedited time frame, within a limited drainage easement, and without adversely affecting the 100-year floodplain. This case history summarizes the project background and design goals/constraints; the geotechnical design of the drilled soldier pile and lagging wall, stacked limestone block wall, and reinforced slopes; the construction of the bank stabilization system; and an overview of project accomplishments and lessons learned.

Rapid drawdown is an important condition controlling the design of the upstream slope in embankment dams and levees. This paper presents the upstream slope failure at San Luis Dam as a case study for performing effective stress drawdown stability analyses. In effective stress analyses, stress-dependent drained shear strengths were used for the fine-grained core and slopewash materials. The seepage-induced pore-water pressures were estimated in the slopewash and fine-grained core by first calibrating the saturated and unsaturated hydraulic parameters with piezometers installed after the slide. The shear-induced pore-water pressures due to the changes in total stress were estimated from Skempton’s A coefficient. The stability analysis methodology incorporates stress-dependent drained shear strength envelopes and shear-induced pore-water pressures to determine the factor of safety (FS). The FS determined at various reservoir levels and slopewash shear strengths are used to provide recommendations for calibrating unsaturated soil properties, integrating seepage-induced, and shear-induced pore-water pressures in stability analyses, and use of commercial software for drawdown stability analyses.

After a newly-completed condominium development was turned over to the homeowners’ association (HOA), an independent engineer identified rock slopes with potential failure scenarios near the rear of the condominium buildings. The HOA’s attorney asked GZA GeoEnvironmental, Inc. (GZA) to conduct a preliminary rock slope evaluation to assess hazards and mitigation measures. Field mapping of bedrock features was conducted using a compass and a laser-scanning survey of the rock slope, and the results were used to evaluate potential instability and rockfall risk. Field mapping was completed either on foot, from a ladder, or by ropes-access. Through our evaluation, it was concluded that rockfall had a high potential to enter backyards and/or impact buildings. The HOA and their attorney elected to address the instability and rockfall concerns and contracted with GZA to design a slope stabilization system. Plans and specifications were developed for mitigation including rock dowels, wire mesh, and spiral rope net. The attorney and HOA then retained GZA to provide bid support, as well as full-time construction administration to ensure that the remediation was constructed in accordance with the plans and specifications.

This paper presents a case study of a tunnel foundation modification design in an area of mild squeezing conditions. During the excavation of the Klokova double tube rock tunnel in Western Greece with a length of almost 3,000 m, a folded flysch zone of about 50 m length was unexpectedly encountered among the hard limestone rock mass. Due to the fast construction pace, two tunnel segments were constructed in the flysch zone using an open final lining cross section designed to provide sufficient support to the limestone. Such an open type section was considered inappropriate to support the soft flysch formation due to the development of a small plastic zone around the tunnel and mild squeezing conditions. As a result, the construction of a horizontal foundation slab connected to the existing footing of the tunnel lining was proposed that would transform the open cross section to a closed section in order to efficiently support the flysch mass pressures. Further to the foundation slab construction, the displacement restraint of the overall foundation was accomplished via micro piles and passive steel anchors under the slab and the original foundation respectively.

This paper presents a case study of staged construction and slope failure of embankments built in swamplands. A roadway embankment was constructed incorporating wick drains and surcharge in a staged sequence to accelerate the construction and maintain slope stability. During the staged embankment construction, initial crack development was observed but subsequently stabilized with the removal and regarding of the fill. However, after a placing a subsequent fill lift, a second more significant occurrence of cracking and slope movement developed, which eventually extended and grew wider as a sign of slope failure. The case was analyzed using limit equilibrium models. The computed settlements, excess pore pressures, and displacement were compared with field measurements and indicated that the wick drains may have stopped effective functioning after being locally kinked or severely bent after the initial slope displacement. This did not provide the required pore pressure dissipation. Analysis results show good agreement between the measured and the computed behaviors with the wick-drain kinking effect and proof that wick drain kinking should be an important consideration during staged fill placement.

Boston is notorious for challenging soils. The highly organic peat and variable fill soils littered throughout the city commonly result in risk of unfavorable settlements of buildings if supported on shallow foundations or the need for expensive deep foundation solutions. However, due to advancements in ground improvement, aggregate piers, and rigid inclusions are rapidly becoming a preferred foundation solution at such challenging sites. This paper discusses one such site, for which both rigid inclusions and aggregate piers were used to reinforce urban fill and organic soils for support of a 5-story parking garage and the surrounding mixed-use structures. The paper walks through the ground improvement solution, the innovative quality control program used during construction, and the results of the load testing program. Ultimately, the rigid inclusion elements exceeded the performance requirements for the project and provided suitable support and settlement control for the proposed structure. This project is of particular importance because it demonstrates that the QC method used for rigid inclusion installation is a key consideration in verifying the element quality and capacity.

Prefabricated vertical drains (PVDs) used for embankment construction over saturated soft cohesive soil deposits accelerate consolidation and reduce construction time by reducing the drainage path from tens of meters to 1–2 m. The current design methodologies assume undrained conditions in the cohesive soil deposit even after PVD’s are installed. This assumption is appropriate if the deposits are sufficiently thick such that excess pore pressures generated during construction do not dissipate before the next lift of soil is placed. However, for most cohesive soil deposits the drainage capability is significantly improved immediately after the installation of PVDs and the assumption of undrained conditions for design is overly conservative. This design assumption may render an embankment construction unfeasible unless ground improvement techniques are used to significantly enhance the foundation strength. This paper presents a hybrid drained-undrained (HDU) model for construction of embankments over soft soils that accounts for the improved soil drainage conditions after installation of PVDs and incorporates the drained shear strength of foundation soils as a function of the embankment construction time. A field case study is presented where the use of HDU model to analyze PVD installation helped construction of a mile long MSE berm in soft soil deposit without need for additional foundation improvement, thereby providing significant cost savings for the project.

Between 2000 and 2008, numerous multi-unit apartment buildings were constructed as part of an apartment complex in Missoula, MT. The wood frame structures were supported on spread footing foundations with slab-on-grade floor systems. Portions of the site transected Moose Canyon gully, which had been filled with undocumented material throughout the previous three decades. Several buildings constructed across the poorly backfilled gully experienced differential settlements of between 8.1 and 23.9 cm (3.2 and 9.4 in.) after construction, while other buildings in the development outside of the gully limits experienced no appreciable settlement. After a construction defect lawsuit was settled, compaction grouting was selected to remediate the foundation soils due to the limited demolition work required, the effectiveness of the technique, and its cost effectiveness. Compaction grouting was used to improve the undocumented, fine-grained fill to depths ranging from 1.8 to 13.7 m (6–45 ft) and create stiff inclusions within the variable fill at approximately 2.4 m (8 ft) on center. The building was releveled to a serviceable condition by using compaction grouting and targeted lifting methods. Compaction grouting successfully raised the structure to a maximum differential elevation of approximately 5.1 cm (2 in.). The compaction grouting approach, lifting methods, field observations, lessons learned, and building performance are discussed herein.

Geotextile tubes are used in dewatering applications over many decades for a variety of slurries, sediments, and wastes. With the increased use of geotextile tubes dewatering in recent years, the desire to maximize both the dewatering rate and retention lead to the use of chemical coagulants and flocculants, which has become a standard practice in geotextile dewatering projects. A variety of small-scale, medium-scale, pilot-scale test methods, and models are used to predict geotextile tube dewatering performance in field. In addition, analytical models have been developed using pilot-scale test and pressurized 2-dimensional dewatering test (P2DT) to predict the dewatering behavior in field and in the lab. These analytical models can be used to predict the dewatering behavior under alternative conditions, including the changes in pumping rates, solids concentration of the slurry, number of dewatering cycles, dewatering duration, final solids concentration of filter cake, and in cumulative volume of slurry. Analyzing the alternative dewatering scenarios using analytical models prior to full-scale implementation, without conducting many dewatering performance tests, is a great benefit in terms of time and money. This study focuses on a geotextile dewatering project of a glue industry settling pond, and the material had different geotechnical properties from the traditional dredged sediment. Multiple lab and field tests were conducted in this study and analytical model was used to evaluate the dewatering performance of geotextile demonstration tests (GDT) in the field. It was found that GDT results were close to the P2DT results and the analytical model successfully predicted GDT results.

In 2013, the Texas Department of Transportation (TxDOT) awarded the Loop 1604 Western extension design build project in San Antonio, TX. This project included testing for the design new pavement and improvement of existing pavement. Various non-destructive and destructive tests were performed during design, such as, falling weight deflectometer (FWD), pavement cores, laboratory resilient modulus, dynamic cone penetrometer (DCP), and other necessary laboratory tests. Green and sustainable innovations such as re-usage of existing aggregate base or retained/rehabilitate pavement sections were also explored. This provided savings on overall project cost and schedule. This paper will focus on the various testing procedures used on the project, challenges during design and during construction, quality control and ssurance (QA/QC), sustainable pavement design alternatives used and lessons learned during the process. The paper also presents the importance of team work and partnering with contractors.

This case study addresses the advancements of women geotechnical engineering faculty in the U.S. over the past 30 years. In 1989, there were just eight women geotechnical faculty in the U.S. Today, we estimate that there are more than 80. Since 1989, there have been various efforts to increase the number and visibility of women geotechnical faculty, including NSF-funded workshops in 1989, 2003, and 2017; listservs and technical committees designed to connect women faculty and/or professionals; and networking efforts to develop and maintain connections between men and women geotechnical faculty for the purpose of enhancing the potential for collaboration between academia and industry. We discuss the various efforts, their successes and failures, and the lessons learned from these efforts.

This paper is an update of a 2010 snapshot in time of the personal backgrounds, educational training, and professional ranking of America’s research-active geotechnical faculty members. Important questions are raised not only as to issues of age, gender, and nationality, but as to where the professoriate in geotechnical engineering is coming from, what level of experience they are bringing to their positions, their professional standing, and to what extent these items have changed over the past 7 years. The results of this paper raise several important insights as to the retention and progression of women and minorities in the ranks of the professorate. Collectively these show an uneven set of advancements for the geotechnical profession and offers some possible reasons for this.

In areas where hydrocarbons are present near the ground surface (e.g., Southern California and Alberta, Canada), tar sands can significantly affect the geotechnical design of building excavations and foundations. In urban areas such as in central Los Angeles, tar sands create geotechnical challenges for large civil projects, including skyscrapers and subway systems. Although tar sands are found throughout the world, the geotechnical literature on the subject is relatively sparse, and mostly deals with their mining, waste disposal, and environmental aspects. This paper describes a case history of the design and construction of the new academy museum of motion pictures in central Los Angeles. This project is located in the Los Angeles County museum of art campus, adjacent to the famous La Brea Tar Pits. This case history describes the challenges associated with designing foundations in tar sands and a full-scale deep foundation load testing program to interpret tar sand strength, and develop skin friction and end bearing values for augercast piles. Our study found axial capacities that were greater than anticipated using conventional methods, which allowed us to reduce the number of required piles, and realize substantial savings in the foundation cost. We believe the approach described in this case history may be used by other practitioners to better characterize tar sand geotechnical properties and optimize their foundations and shoring designs.

This paper describes the shallow foundation design and construction for the new single span heel trunnion bascule bridge over “The Gut” in South Bristol, ME. The Gut Bridge carries Highway 129 over “The Gut”, a small channel separating Rutherford Island from the mainland. The channel is subject to a twice daily tidal variation of nearly 10 ft (3.048 m). The Gut Bridge is one of the most frequently opened bridges in the country due to the very low vertical clearance between the bridge structure and mean high water. The proposed structure consists of a single leaf bascule span with two slot bascule pits, new abutments, and wing walls supported on shallow foundations. The paper also describes how the unique constraints and subterranean conditions of the project site led to the selection of a spread foundation to support the bridge.