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By Dimitrios Polantzas P. E., Collin E. Sweeney E. I. T., Franklin M. Grynkiewicz P. E., Leili Javidanian P. E.

In the latest AASHTO design specifications, the Load and Resistance Factor Design (LRFD) method is prescribed for the design of retaining walls. However, inconsistencies arise when LRFD is used for retaining wall design versus the traditional Allowable Stress Design (ASD). Required toe embedment and wall loading demand vary greatly when the two design approaches are compared, all else being equal. This is due to application of linear load factors to properties that vary non-linearly in the design. These inherent inconsistencies are further intensified when introducing factors such as layered soil profiles, different wall types, groundwater elevation, and surcharge requirements. When applied correctly, these two design approaches, in theory, should lead the designer to the same result with little discrepancy, as they do with steel structure design. However, the use of the current AASHTO LRFD method for various geostructural retaining wall designs yields contradictory results that suggest existing retaining walls that have been successfully designed and constructed are unstable. Fundamentally, LRFD should be built on reliability-based calibrations; the successful past performance of existing retaining structures designed using ASD suggests that the LRFD approach requires considerable modification. The authors of this paper recommend that the current LRFD load factors be reviewed and revised based on more comprehensive wall performance data and wall type such that the difference between retaining structures designed using LRFD and those designed using ASD is eliminated.

Oct 1, 2022

By Pete Howell, Patrick Granitzki, Alicia Plinio, Janitha Batagoda

The New York City Housing Authority (NYCHA) Red Hook Houses was subjected to damage during Superstorm Sandy. As a result, the NYCHA has an ongoing project known as Restoration Associated with Sandy Recovery Program to improve the resistance against future storms. The specific project included 28 residential buildings and several service buildings within the Red Hook Development. The subsurface conditions within the eastern portion of the site included existing fill material underlain by varying stratums of very loose, loose and medium dense silty sands followed by very soft to medium stiff clay or dense silty sands. The western portion of the site included existing fill material, very loose to medium dense silty sands and organic clayey silts underlain by very soft to medium stiff sandy silts. Based on the geotechnical report, a conventional driven steel pile system was specified containing two pile depths. As part of the project bidding, an alternative pile type was recommended and analyzed to provide quicker installation, reduce vibrations, reduce noise, and provide relatively large cost savings. Due to relatively high lateral loading, an innovative double steel casing drilled displacement piles was proposed as the alternative pile option. Field testing proved the piles capable of the required project capacities and the use of drilled displacement piles as the best alternative for the project and accepted by the NYCHA.

Oct 1, 2022

By Sudhir Kumar Das

"The exorbitant price of the land in the metropolis has restricted the horizontal expansion and compelled the owners, the developers and the engineers to opt for vertical expansion. This has resulted in the construction of high rises by extending floors of the existing buildings and developing the new ones for which deep excavation is a must. The multistoried buildings up to a certain height can be founded on shallow depth if the soil beneath can withstand the load. If not, the soil can be stabilized by the latest improvement technology to change the properties of soil to cater the desired load of the superstructures. By such practice the cost and time of completion of the substructures can be reduced in comparison to the substructures needed for deep excavation.The necessity of deep excavation cannot be ignored to create housings, underground parking lots and the other public amenities for the urban migrants in the metropolis.Although most of the metropolis have underground mapping the developers, before starting excavation should be hundred percent sure about the alignment and depth of the utilities so that the excavators do not snap the same to bring cut in water supply, power lines, telephone lines etc, resulting in hue and cry in the neighborhoods of the metropolis due to no availability of the essential services The building/structures coming on the influence zones of the deep excavation should be monitored in all sequences of excavations. In case of building underground corridors for rail or road through open deep excavation under a traffic road the developers, before commencing excavation should shift/divert the dry and wet utilities coming on the way of excavation to suitable locations. The surface traffic need to be diverted either temporarily to an adjacent alternative road or allowed to pass over a decking built over the trench of excavation for the affected length of construction. The soil support system is necessary longitudinally on the two sides covering the width of trench for building corridors. In case of building substructures of flyovers built at different plots along the alignment of the flyover or a multistoried complex built at an isolated plot, the soil support system would be necessary on all the sides covering the plot of construction.The material of construction of soil support depends on the depth, type of soil and the type of permanent structure to be developed. Probable geo-hazards inviting casualties in the deep excavation projects occur due to caving of soil, leakage of wet utilities, seepage through honey comb concrete surfaces, failure of pump used for dewatering etc. A detailed comprehensive planning, management and determination of the project authority is essential for marginalizing the casualties. These prevent unforeseen expenditure in mitigation and help to control the time and the cost over run of overall project. The engineer at site should be more a professional manager than an engineer at site. He should be conversant with the safety and environment rules and regulations applicable to deep underground projects."

Jan 1, 2015

By Heman Manchanda, Jyoti Agarwal

Several infrastructure projects are under construction in India; many of them involves construction of deep foundations like reinforced concrete and steel piles to support super structures. As most of the piles being constructed in India are reinforced concrete bored piles, there are always uncertainties relating to the quality of construction, and in this case non-destructive methods to ascertain quality of piles becomes very crucial to success of any project. Non-destructive pile testing is becoming more and more popular with growing technologies wherein geophysical techniques and wave propagation theories are being used for pile quality and length analysis. Low-strain pulse echo method and cross-hole sonic logging testing are two pile integrity testing techniques being currently practiced in India which are cost effective and provides reliable near accurate results if analyzed properly. Paper presents current practices being adopted in India for conducting these two tests, highlighting the critical site considerations and analysis techniques. The paper also discusses various execution and interpretation challenges faced by practicing engineers and recommends a way forward.

Sep 1, 2022

By Venkatesh S. V J, Shubha M, Srilakshmi G

Choosing for the best option of pile foundations to overcome large lateral and uplift loads for the foundations in transmission line towers/offshore environment is still being a concern to achieve the required capacities but also by considering the suitability aspect in the environment. The objective of this paper is to review the methods that have been done for knowing the uplift resistance and lateral resistance of pedestal piles. Investigations by different methods such as experimental studies, numerical and analytical studies have been done by various researchers in order to evaluate the response of a belled pile. These methods are discussed in this paper and the comparison with straight shaft pile based upon the test and analysis. The results indicated that the uplift resistance and lateral resistance were significantly increased with the adoption of belled piles than straight shaft piles.

Sep 1, 2022

By M. Hesham El Naggar, Mehdi Heidari

"Equivalent fixed-base cantilever model is a common approach for performance base seismic design of bridge structures supported by extended pile-shaft. In this method, global displacement ductility factor is related to local curvature ductility demand by assuming a concentrated plastic hinge at location of maximum bending moment. Equivalent plastic hinge length is one of the key parameters that should be assumed accurately in kinematic expression of the cantilever model. Although, some expressions have proposed to estimate the length of the in-ground plastic hinge; however, these relations yield differing results. In this paper, a general expression is derived based on the concept of distributed plasticity to predict the plastic region of yielded piles in clay and sand. A length modification factor is defined to relate the equivalent length of plastic hinge to the real plastic zone. Then, results from nonlinear pushover analyses are used to propose an equation for the modification factor as a function of displacement ductility factor.IntroductionDuring severe earthquake events, development of the plastic hinge in pile foundation below ground level is inevitable for bridge structures supported on extended pile-shafts. A common approach for seismic design of the yielding pile-shafts is to replace the pile-soil system by an equivalent fixed-base cantilever assuming the equivalent system has the same global response as that of the pile-shaft (Budek et al. 2000; Chai 2002). In this method, plastic curvature is concentrated at the center of the equivalent plastic hinge below ground surface. Prior knowledge of plastic-hinge length is essential for proper assessment of assess plastic displacement at the top of the pile-shaft. Unfortunately, existing recommendations for estimating plastichinge length are largely incomplete and/or inadequate.During the last two decades, several relationships have proposed for evaluating the equivalent plastic hinge length, Lp, based on experimental and numerical studies. Budek et al. (2000) conducted numerical modeling to calculate the plastic-hinge length of piles embedded in cohesionless soil. They found that the plastichinge length varies linearly with both soil stiffness and aboveground height, e. Chai and Hutchinson (2002) conducted full-scale experimental tests on reinforced concrete piles in sand. They reported that Lp depends primarily on the aboveground height of the pile, neither sensitive to the soil stiffness nor to the value of displacement ductility factor. They stated that the equivalent plastic hinge length is relatively independent of the displacement ductility factor and is not very sensitive to the change in soil density. On the contrary, Goel (2014) and Liu et al. (2016) conducted nonlinear numerical analyses which revealed that Lp changes with the displacement ductility factor and even suggested that using different values of Lp for different seismic design levels is essential for a reliable estimation of the ductility capacity."

Jan 1, 2017

By James L. Christensen, Gregory Sanchez, Michael P. Walker

The Fogg Museum expansion project required excavation and construction in a congested urban area in Cambridge, Massachusetts. A soldier pile tremie concrete (SPTC) wall provided the support of excavation and now serves as the permanent basement wall of the new expansion of the museum. The existing Fogg museum had a single basement level. The new expansion has a two-level basement for new exhibit space and an amphitheater. The east side of the site is about 20 feet above the basement level of the existing Fogg structure which resulted in a significant unbalanced load that needed to be resolved without damaging the original Fogg structure. The SPTC wall was supported with a combination of tiebacks and internal bracing. The final depth of the excavation was about 40 feet below street level. Strict movement control was imposed because the existing museum contained an Italian Renaissance-style courtyard. The southeast corner of the SPTC wall had to accommodate underpinning of an historic concrete ramp which was ultimately incorporated into the expansion. Challenges during construction included excavating the SPTC wall panels up to 12 feet into argillite bedrock which had occasional diabase dikes and sills. The following topics are discussed in more detail after a general project.

Jan 1, 2015

By Scott D. Neely, Donald R. Clark

"An existing landslide located at the southeast corner of the Telluride Regional Airport has been in an active state of failure for several years. The presence of the landslide has represented an on-going liability for the Airport, the Federal Aviation Administration and the Colorado Department of Transportation. A catastrophic failure of this landslide occurring in a manner similar to that which occurred at the Airport in 1987 has posed an on-going threat to closing Colorado State Highway 145 south and below the slide area. The existing landslide has been characterized as a series of multiple failed block areas located downhill of the airport runway that have occurred in severely weathered Mancos Shale.A total of 12 alternatives were evaluated to mitigate the landslide, including the preferred alternatives of either partial or total landslide removal. However, prior development has left essentially no place on the airport property that would allow for the disposal of the landslide debris for either the total or partial removal alternatives, and the closest off-site disposal area was approximately 40 miles from the site. As a result, in-situ stabilization of the landslide, including a primary system of isolated tie-back anchor plates with strand anchors, and a secondary system of high strength steel mesh and intermediate anchors was selected for the ultimate design of the project to stabilize the landslide in place.For design purposes, geotechnical characterization of the slide area was accomplished through geological mapping, conventional borehole exploration and geophysics using multiple electrical resistivity. The paper discusses the design process utilized and the unique challenges faced one-third of the way through construction when discovery of a survey error required redesign of the entire landslide mass stabilization system using the prefabricated anchors that had already been delivered to the project.INTRODUCTIONTelluride Colorado is located at the toe of the Colorado Rocky Mountains on the western slope. The Telluride Regional Airport is located on Deep Creek Mesa about 5 miles west of the town of Telluride.The landslide is located at the southeast corner of the airport just below an abandoned portion of the quarry access road on a south facing slope. The quarry access road is located below the elevation of the runway and outside the elk fence that surrounds the air traffic area of the airport property. Since the reconstruction of the runway, the access road to the quarry and the construction access road for the reconstruction of the airport runway and safety area were rerouted to stable ground north of the previous access road location and off of the head scarp of the landslide."

Jan 1, 2015

By Dipl. -Ing. (FH) Thomas Schmitt, Dr. Melvin England

Foundations in Geneva are difficult and expensive due a large overlayer of clay and silt above competent bearing material in the moraine. Common foundation schemes use deep barrettes or bored piles, first passing large, weak layers of soil before finally reaching acceptable, solid moraine with reasonable values of skin friction and end bearing resistance, thus requiring further deep penetration for the necessary length for load transfer in the moraine. Depths of more than 60 m (200 ft) in Geneva are common in this region. At the Onyx-Project Geneva Implenia Foundation Company also encountered these circumstances. Despite usual solutions Implenia referred to an old and well known, but still intelligent and in today’s words smart, efficient and economical solution. Using small shafts, passing the large layers of clay and silt, ending with the pile toe in the underlaying moraine with a belled or underreamed base was the technic adopted to save drilling time, reduce spoil and concrete, so finally reducing the CO2 footprint. Piles with enlarged base (“belled” or “underreamed”) are reported at the beginning of the 20th century, for example at Chicago, which has a quite similar geotechnical structure as Geneva with the need of deep foundations. The first pile base enlargements were built in hand-dug caissons with wood lagging and steel ring bracing. In the 50s and 60s piling works were more and more mechanized, driven by the development of more powerful cranes and specialized drill rigs. Additionally the first tools for mechanized base enlargement were invented around that period. This report describes the project situation at Geneva, the drilling and enlargement technique of the pile base, the verification of the design values with an in-situ bi-directional load test and the smart execution by reduction of CO2 and costs.

May 1, 2022

By Ganesh Deepak K., Anjana R. K., Dr. Kumar Pitchumani N., Rajasekharam R. M. V. M. S. S.

The Phase 2 of Chennai Metro is being introduced in the city to ease the dependence on the existing transportation systems. Phase 2 is a combination of underground and elevated metro stretches comprising of three corridors. The current study focusses on the underground stretch of Corridor 3 which has a total of 29 underground stations. Construction of the underground cut and cover stations results in ground movements, which in turn impact the structures adjacent to the excavations. The greenfield ground settlement can be evaluated with the help of empirical approach or an approach requiring finite element modelling (FEM). The paper compares empirical and FEM approaches with regards to ground conditions in Chennai. Further, with the predicted ground settlements, building damage assessment is performed. The damage category of a building is defined based on the estimated tensile strains. This paper also compares the building damage assessment with empirical method and finite element modelling.

Nov 1, 2022

By A. V. Rose

A redevelopment in the City of London has been constructed with a piled foundation system that is believed to be the first of its kind. The purpose of the research is to explore this novel foundation method, which involves the installation of closely spaced piles in a perimeter arrangement with a body of soil enclosed in the centre. Both centrifuge modelling and numerical modelling techniques are used.

Jan 1, 2011

By George Piscsalko

Quality control of drilled shafts and ACIP piles is greatly dependent upon the practices of the site personnel. In many applications it is difficult to properly inspect the shaft prior to concreting, such as when the shaft is drilled under slurry. In other cases, such as ACIP piles, it is impossible to inspect the shaft in any manner prior to concreting. There are numerous methods currently available to assess the integrity of drilled shafts and ACIP piles. Each method has its advantages and limitations. This paper will compare the various available methods as well as introduce a new method for assessing integrity in drilled shafts and ACIP piles. This new method, known as Thermal Integrity Profiling, determines the integrity over 100% of the shaft both inside and outside the reinforcing cage by measuring the hydration temperature of the concrete along the length of the shaft. These temperature measurements can be made by either passing a thermal probe through a standard Cross Hole access tube typically 12 to 48 hours after concrete placement, or from embedding thermal wires within the shaft prior to concrete placement and monitoring them with unattended data collectors for 12 to 48 hours after concrete placement. This Thermal Integrity Profile method will be described in detail and several case histories will be presented. Additional testing methods which will be compared include low strain Pile Integrity Testing, and Cross Hole Sonic Logging. Advantages and limitations for each method will be discussed.

By Lance Rasband, Richard Hanke, John Starcevich

"The 17.4 meter (57 ft) diameter tunnel boring machine (TBM), the world’s largest at the time of her launch in 2012, locally referred to as “Bertha,” is stuck. Incapacitated due to mechanical failure approximately 36 meters (120 ft) beneath downtown Seattle, situated precariously between the deteriorating Alaskan Way Viaduct and the failing Seattle Seawall. Accessing Bertha with a vertical shaft provides the best approach to address all facets needed for repairs and will allow the full removal of Bertha’s cutter head and related inner workings. Limited area above the tunnel alignment and the physical restrictions of existing infrastructure, create significant challenges for the design of an otherwise symmetrical shaft, requiring special attention to design and layout. Consequently, the access/recovery shaft design required a combination of 3m, 2.5m, 2.2m, 1.5m and 1m diameter unreinforced drilled secant piles coupled with various ground improvement techniques and dewatering, to fully satisfy the shoring design requirements. This paper will describe the shaft installation procedures, equipment used and pitfalls encountered while undertaking access shaft construction of this magnitude.INTRODUCTIONTunneling on Seattle’s SR99 tunnel project began in July of 2013. After slowly mining through a 4.5 m (14.76 ft) thick fiber-reinforced concrete headwall and the first of three stabilized “safe havens,” Bertha would proceed along the proposed alignment through 122 meters (400 ft) of jet grout improved soil at a rate of slightly over 1.6 m (5.25 ft) per day. Once past the improved area, it was planned that “Bertha” – would be moving at a rate of about 11 m (36 ft) per day. By the end of October 2013, Bertha had mined roughly 131 m, (430 ft) averaging 1.4 m (4.6 ft) per day and had begun mining within native soils. By December 2013, tunneling had reached the 244 m mark and Bertha was averaging 3.6 m (11.8 ft) per day, achieving as much as 12.8 m (42 ft) of progress on given days. Unfortunately, on December 6th, 2013, Bertha began to stumble and all progress quickly came to a halt.It was initially reported that an obstruction had stopped Bertha in her tracks. The preliminary investigation involved installation of 10 deep dewatering wells to reduce the hydrostatic pressure around the TBM, and allow visual inspection of the cutter head from within the TBM, and also to investigate for the presence of obstructions at the face of the cutter head. During this inspection, fragments of steel pipe were discovered entangled in the cutter head. The fragments were apparently from an abandoned 254 mm (10 in.) diameter monitoring well casing, previously installed by WSDOT to monitor ground water conditions for the design and planning of this tunnel project. After the steel was removed from the cutter head and cleared from Bertha’s path, tunneling resumed. It was then discovered that Bertha was only able to generate a slow crawl."

Jan 1, 2016

By Suthan Pooranampillai

This paper presents a case study of the use of single axis cement deep soil mixing (CDSM) to deal with static settlement and seismic stability of the foundation soils under a reinforced soil slope (RSS) embankment up to 50 feet high. As part of the widening of Interstate 5 (I-5) to allow High Occupancy Vehicle (HOV) lanes in Tacoma, Washington, a new approach and span over the Puyallup River will be constructed. During the soils investigation and design phase of the project, low plasticity silts (ML) inter-bedded with silty sand layers and organic silt where identified as being potentially liquefiable. CDSM was selected to address the embankment foundation concerns and allow for future trenchless installation of utility lines beneath the embankment. The presence of a confined, artesian aquifer within the design depth of the CDSM led to the installation of a depressurization system to avoid an upward gradient through the wet soil-cement. In addition to addressing the design approach, the paper discusses the challenges associated with quality assurance of CDSM within the time constraints of an ongoing project. The limited recovery rate of conventional triple tube coring in the soil-cement and double tube wet sampling led to the use of sonic coring to provide a near continuous core of the soil-cement.

By Jeremy Butkovich

Dynamic soil-structure interaction (DSSI) analyses are becoming more common in bridge designs, especially in seismically active areas. Because of its proximity to two active fault zones, the Evergreen Point west approach bridge replacement will be base isolated, and will be designed using DSSI. The project team completed two independent bridge designs to satisfy peer review requirements. The designs required substantial characterization of the soil dynamic behavior using both laboratory and in-situ testing. The analyses made use of earthquake time histories spectrally matched to conditional mean spectra. This led to reduced, and more realistic seismic demands on the structure, compared to conventional uniform hazard spectrum matching. The bridge analyses suggest that the preliminary bridge design is relatively conservative. This will allow the design team to potentially reduce shaft/column diameters and reinforcement. The design team estimates that the dynamic analysis design could represent a net savings of around $60 to $90 million compared to a conventional design.

By George Piscsalko

"Quality control of drilled shafts and ACIP piles is greatly dependent upon the practices of the site personnel. In many applications it is difficult to properly inspect the shaft prior to concreting, such as when the shaft is drilled under slurry. In other cases, such as ACIP piles, it is impossible to inspect the shaft in any manner prior to concreting. There are numerous methods currently available to assess the integrity of drilled shafts and ACIP piles. Each method has its advantages and limitations. This paper will compare the various available methods as well as introduce a new method for assessing integrity in drilled shafts and ACIP piles. This new method, known as Thermal Integrity Profiling, determines the integrity over 100% of the shaft both inside and outside the reinforcing cage by measuring the hydration temperature of the concrete along the length of the shaft. These temperature measurements can be made by either passing a thermal probe through a standard Cross Hole access tube typically 12 to 48 hours after concrete placement, or from embedding thermal wires within the shaft prior to concrete placement and monitoring them with unattended data collectors for 12 to 48 hours after concrete placement. This Thermal Integrity Profile method will be described in detail and several case histories will be presented. Additional testing methods which will be compared include low strain Pile Integrity Testing, and Cross Hole Sonic Logging. Advantages and limitations for each method will be discussed.IntroductionDrilled shafts and Augered Cast-in-Place (ACIP) piles have been increasingly used over the past several years due to several reasons including the reduced noise and vibration, speed of installation for ACIP piles, and the large axial and lateral capacities which are attainable for very large drilled shafts. ACIP piles are drilled and cast without any visual inspection. Drilled shafts can be cast in a dry hole which allows for inspection of the hole prior to casting, but the casting process is very difficult to nearly impossible to inspect with any accuracy. Drilled shafts are frequently cast under slurry as a means to stabilize the surrounding soils during the construction process. When casting a drilled shaft under slurry, it is very difficult to accurately inspect the hole prior to casting and it is equally difficult to inspect the shaft during the casting process. Many of the above mentioned processes are blind to inspection and therefore the chances increase for having defects present in the completed elements."

Jan 1, 2017

By H. Hayashi, M. Yamaki, H. Hashimoto, T. Yamanashi

"In an experiment on a trial embankment, the deformation mode of the improved ground at the toe of the embankment was compared with the deformation mode of the unimproved ground. This comparison showed that the behavior exhibited by the improved ground was the same as that exhibited by the unimproved ground, despite the low improvement rate (ap = 10%) of the ground improvement. Thus, the improved ground and the unimproved ground were found to be functioning as composite ground. Further, the strain that developed in the geo-textile used for the crushed-stone mat was considerably less than the strain specified by the design strength. As a result, it was found that a crushed-stone mat can serve as a mattress.OVERVIEW OF THE TEST CONSTRUCTIONLow Improvement-Rate Soil in Combination with Crushed-Stone MatIn Hokkaido, approximately 2,000 km2 of the land is peat land, an area almost as large as Tokyo. Such land accounts for 6% of Hokkaido’s plains and 2.4% of its total land area. The peat layer is normally 3 to 5 m thick and underlain by a layer of soft, cohesive soil whose thickness may exceed 20 m. In such a ground, consolidation using cement may generate differential settlement between improved soil as a result of embankment construction or lateral deformation caused by the slipping of unimproved ground. Therefore, the improvement ratio (ap) is designed to be at least 50% by the Manual for Construction on Soft Peaty Ground (CERI, 2011 [1]). Consolidation of ground with a low improvement ratio in combination with crushed stone-mat installation is a measure for soft ground (Figure 1). In this method, soil with a lower Improvement ratio than that of conventional improved soil (e.g., ap=10%) is placed beneath the entire embankment and a “crush stone mat”, a layer of crushed stone (t=0.5 m) enclosed by geo-textile, is then placed between the embankment and the soil."

Jan 1, 2015

By Arjan Jovani, Arjan Beqiraj, Përparim Alikaj, Altin Karriqi

"Koman dam is one of most important high dams in Drin River Cascade. Safety of these dam is very important not only in power production but also in social and environmental aspects connected with vital activity of local people living in downstream of Drini River and in economic development of the country. In December 2014, during the rehabilitation works on some protection measures at the downstream dam toe, a considerable amount of water leakage emerged from the dam toe. This was noticed even before, but its amount and physical-chemical properties were not evaluated. In order to study the origin and flow direction of this water leakage, KESH sh.a. (Albanian Power Corporation) realized Geophysical and Hydro chemical surveys, turbidity and flow measurements and respective analyses of them. Geophysical survey consist in Apparent Resistivity surveys and Self Potential survey. The survey was done in 3 lines using Resistivity “Real Section” technique. Results are plotted in Sections and plan maps of resistivity and SP parameter. There are defined possible leakage areas and the main flow directions are defined. Also, there is done a hydro chemical analyse. Nine water samples were taken from the different places as Komani lake, service galleries of dam, dam toe and two karst springs which were analysed for both physical-chemical parameters and isotopic composition of O-18 and D. The attained analytical data found that water from the dam toe leakages shows the same chemical signature and isotopic composition of O-18 and D as the water from the lake, thus confirming the hydraulic connection between them.Also, There is done the analyse of water leakage turbidity and amount of this leakage"

Jan 1, 2016

By Dominic Parmantier, Karen Dawson, Suthan Pooranampillai, Seungcheol Shin

"This paper presents a case study of the use of single axis cement deep soil mixing (CDSM) to deal with static settlement and seismic stability of the foundation soils under a reinforced soil slope (RSS) embankment up to 50 feet high. As part of the widening of Interstate 5 (I-5) to allow High Occupancy Vehicle (HOV) lanes in Tacoma, Washington, a new approach and span over the Puyallup River will be constructed. During the soils investigation and design phase of the project, low plasticity silts (ML) inter-bedded with silty sand layers and organic silt where identified as being potentially liquefiable. CDSM was selected to address the embankment foundation concerns and allow for future trenchless installation of utility lines beneath the embankment. The presence of a confined, artesian aquifer within the design depth of the CDSM led to the installation of a depressurization system to avoid an upward gradient through the wet soil-cement. In addition to addressing the design approach, the paper discusses the challenges associated with quality assurance of CDSM within the time constraints of an ongoing project. The limited recovery rate of conventional triple tube coring in the soil-cement and double tube wet sampling led to the use of sonic coring to provide a near continuous core of the soil-cement.IntroductionCement deep soil mixing (CDSM) was used as a replacement for stone column ground improvement in a corridor which the owner, the Washington State Department of Transportation (WSDOT) wanted to reserve for future trenchless crossings beneath reinforced soil embankments within a freeway interchange. The work was part of HOV improvements to I-5 in Tacoma, Washington. The CDSM construction occurred in late 2010 and early 2011.Approximately 14,500 cubic yards of soil cement columns were placed by CDSM. The soil cement improved ground supports permanent geosynthetic reinforced slopes up to 50 feet high. The ground improvement was designed primarily to provide global stability of the reinforced slopes during seismic loading, but it was also utilized to reduce the time and total amount of settlement following construction of the embankments.This paper presents a discussion of the design approach and challenges associated with quality assurance of a relatively small volume of CDSM within the time constraints of an ongoing project. The challenges associated with attempts at collecting cores of the cured soil-cement mix cured by triple tube coring and pushing a double tube into the wet mix and allowing it to cure insitu are discussed, along with the eventual adoption of sonic coring combined with reliance on laboratory testing of wet mix samples collected daily."

Jan 1, 2017

By Greg Nutson, Jeremy Butkovich, Bill Perkins, Hollie Ellis, Paul Bott

"Dynamic soil-structure interaction (DSSI) analyses are becoming more common in bridge designs, especially in seismically active areas. Because of its proximity to two active fault zones, the Evergreen Point west approach bridge replacement will be base isolated, and will be designed using DSSI. The project team completed two independent bridge designs to satisfy peer review requirements. The designs required substantial characterization of the soil dynamic behavior using both laboratory and in-situ testing. The analyses made use of earthquake time histories spectrally matched to conditional mean spectra. This led to reduced, and more realistic seismic demands on the structure, compared to conventional uniform hazard spectrum matching. The bridge analyses suggest that the preliminary bridge design is relatively conservative. This will allow the design team to potentially reduce shaft/column diameters and reinforcement. The design team estimates that the dynamic analysis design could represent a net savings of around $60 to $90 million compared to a conventional design.INTRODUCTIONThe Evergreen Point Bridge conveys State Route (SR) 520 2.6 miles (4.2 kilometers [km]) from Seattle to Medina across Lake Washington. The bridge is located in a seismically active area, and the Washington State Department of Transportation (WSDOT) has determined that the western half of the 1960s-era bridge (the “west approach”) is vulnerable to earthquake damage. WSDOT has begun preliminary design to replace the west approach bridge.The west approach extends about 6,100 feet (1,900 meters [m]) east from Seattle’s Montlake neighborhood, over Union Bay and Foster Island, then into Lake Washington proper (Figure 1). Approximately 5,600 feet (1,700 m) of the replacement bridge would be constructed over water. Subsurface conditions along the bridge alignment consist of 5 to 80 feet (2 to 24 m) of very soft peat and clay, over very dense/hard sand and clay. Multiple pile supported columns support the existing bridge. The new bridge would be supported by 8- to 10- foot-diameter (2.4 to 3.0 m) drilled shafts that extend about 50 feet (15 m) into the underlying very dense/hard soil. To reduce seismic demands on the bridge superstructure, WSDOT has decided to incorporate a base-isolation system into the bridge design."

Jan 1, 2017