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By Andrew Cushing

This paper presents the design and construction of the foundation for a major high-rise real estate development on the west side of Manhattan. Arup was retained by Underpinning and Foundation Skanska to design a secant pile wall as excavation support for a proposed two-level basement of a new 23-story residential building located at 100 11th Avenue and West 19th Street. The secant pile wall will also act as the permanent basement retaining wall for the new building. The site is bounded on two sides by existing structures and is underlain by a thick deposit of very soft organic silt and clay. Therefore, the potential for ground movements and their impact on an adjacent structure bearing on shallow footings were of the utmost concern. This paper addresses the design and construction considerations associated with this secant wall, as well as installation details. Measured wall movements are also used to assess the validity of the pre-construction soil strength and stiffness design parameters.

Jan 1, 2008

By K. Rainer Massarsch, Bengt H. Fellenius

"Abstract Vibrations generated during the driving of piles or sheet piles can affect buildings or installations in the ground. However, observed building damage is not always caused directly by dynamic effects, but can also be related to foundation conditions. The importance of geotechnical conditions is usually not taken into consideration in most vibration standards. This paper describes how building foundations, and in particular mixed foundation types, are especially sensitive to ground vibrations. A method is presented for assessing the risk of settlement due to vibrations in granular soils. Also, a simple concept is proposed for estimating settlements in the vicinity of driven piles.1. INTRODUCTIONUnder unfavorable conditions, the installation of piles or sheet piles can cause damage to buildings or other structures on the ground. Frequently, such damage is attributed to vibrations of the building itself. In many countries, national or international standards are used to assess the risk of vibration damage to buildings. As such standards are often prepared by engineers with little or no geotechnical knowledge, the effects of ground conditions on vibration propagation and damage to building foundations are generally not recognized, and damage criteria based solely on the dynamic response of buildings neglect the importance of damage mechanisms governed by geotechnical conditions. One potentially important damage mechanism is differential settlement below buildings, especially when these are founded on loose granular soils. When seeking guidance in the literature, little or no information can be found regarding methods to assess permissible levels of ground vibrations with respect to risk for settlement.This paper focuses on building damage that can be attributed to foundation conditions. In the case of ground vibrations due to pile and sheet pile driving, differential settlements are of particular importance as the ground vibrations attenuate relatively rapidly from the source. Consequently, settlement below part of the building, which is located close to the vibration source, can be significantly larger than at a distance further away.Piles are often a cost-effective foundation solution for buildings on loose and compressible soil, frequently located in urbanized areas. Sheet piles are commonly used as support for deep excavations. While impact driving is most commonly used to install piles, vibrators are frequently used for driving (and extraction) of sheet piles. It is important to recognize the fundamental differences between impact and vibratory driving. During impact driving, the pile is subjected to stress waves of short duration. The driving process creates vibrations, which radiate from the shaft and/or the toe of the pile into the soil. The larger the intensity of the stress wave, the larger the dynamic force and the intensity of ground vibrations. In addition to the vibration intensity, which often is expressed in terms of particle velocity, also the vibration frequency is important. When the dominant frequencies of the generated vibrations harmonize with the resonance frequency of buildings or building elements, the risk of building damage increases."

Jan 1, 2014

By David S. Yang

The construction of Oakland Airport Roadway Project for the airport expansion requires stabilization of subsurface soils for the construction of three grade separation structures at two roadway interchanges and the intersection of a roadway and taxiway serving the airport. Loose sandy fills and soft Bay Mud were improved by Cement Deep Soil Mixing (CDSM) for the construction of a soil-cement foundation under the MSE (Mechanically Stabilized Earth) walls of a roadway overcrossing and a soil-cement gravity retaining wall to maintain stability of a roadway undercrossing during and after a major earthquake. CDSM was also used to construct two cutoff walls for groundwater control. A test section was carried out prior to full production to verify that the CDSM equipment, installation procedures, and mix designs could produce the soil-cement with required strength, uniformity, and permeability to meet the design intent. Additional test sections were performed for the confirmation or modification of the mix design and installation procedure to cope with the complex subsurface conditions resulting from the historical development of the site. The test section revealed that the CDSM cutoff walls, retaining wall, and foundation improvements could be constructed to satisfy the design requirements and that the intermittent test sections alleviate the impact of the varying subsurface conditions. Based on the data obtained from the test sections, one CDSM cutoff wall was completed in July 2000. Full production of the CDSM retaining wall, cutoff wall, and foundation began in March 2001 and is expected to be complete in November 2001.

Jan 1, 2001

By Timothy C. Siegel

Given that piles are composed of different materials and installed using a variety of methods, ASTM D 1143/D 1143M-07 Standard Test Methods for Deep Foundations Under Static Axial Compression is justifiably general so that it has as many applications as reasonably possible. There are aspects of the test setup, the test procedures, and data interpretation for instrumented piles (some of which are specific to augered cast-in-place piles) that are either not discussed in detail in this ASTM standard or are not addressed at all. Specifically, the use of variable time hold times can obscure the shape of the conventional load-deflection curve, as well as, influence the interpretation of the ultimate pile capacity. Unload-reload cycles induce additional non-uniform internal axial loads within the pile which complicate interpretation of the strain gage data and increase the potential for errors. Attempts to maintain a constant top load during the hold period can lead to operational difficulties in taking measurements and are technically unnecessary. Residual load has been shown to develop in cast-in-place piles and can significantly influence the axial load distribution as interpreted from strain gage data. The stiffness of cast-in-place piles has been observed to vary with the measured strain, and a constant modulus, as provided by correlation with the unconfined compressive strength of the grout, may lead to a significantly different interpretation of the axial load distribution.

Jan 1, 2010

By Rudolph P. Frizzi

Quality control is essential for augered cast-in-place (ACIP) piles (also known as continuous flight auger (CFA) piles outside the United States) and drilled displacement (DD) piles since the pile is constructed below the ground surface out of the direct sight of the personnel constructing and inspecting the pile. ACIP piles are being successfully constructed to support high-rise structures, hospitals, arenas and stadiums, mass transit systems, and power and industrial facilities. The use of DD pile technology is also gaining ground in the United States, typically utilizing proprietary systems such as Omega (currently utilized by Richard Goettle Inc., and LG Barcus and Sons, Inc.), Berkel, and DeWal (currently utilized by Morris-Shea). Different types of ACIP/DD pile installation equipment are shown in Figures 1 and 2. ACIP piles are installed into granular and cohesive soils, and soft rock to lengths currently approaching 130 ft (39.5 m), with diameters up to 24 to 36 inches (610 to 915 mm), and sustaining design loads approaching 900 kips (4000 kN). Current DD pile installation equipment in the United States is capable of installing up to 79-ft-long (24 m) piles with diameters ranging from 12 to 18 inches (305 mm to 460 mm).

Jan 1, 2004

By Willie M. NeSmith

In the Metropolitan Atlanta Area today, augered, cast-in-place (ACIP) piles will be considered on most projects where deep foundation support is required. ACIP piles were first used in Atlanta in the late 1960s, and application began to blossom in the mid-1980s. Current design practice for ACIP piles is addressed in another paper in this conference. This paper describes the evolution of the ACIP industry in Atlanta, and details the use of ACIP piles on major projects in the Atlanta area.

Jan 1, 2003

By Stefan Swartling, Rudy Lyon, Donald A. Bruce

"Since their first production application in Sweden in 1995, water-powered, down-thehole hammers (WDTH) have been used throughout the world in many different drilling applications, total lines, over 25 million lineal meters of drill hole. This paper reviews the history and principles of down-the-hole drilling (DTH) in general with both air and water, before focusing on the details of WDTH hammers. A summary of the numerous and considerable advantages of WDTH drilling is provided, with particular emphasis on their superior productivity, smaller deviation, applicability in sensitive/urban conditions, environmental protection and much reduced energy requirements.HISTORICAL PERSPECTIVE ON PRODUCTION DRILLING METHODSAir-flushed drilling with top hammers began in the mining industry in Sweden in 1873, while down-the-hole (DTH) drills, again with air flush (and activation) became operational in 1950. During that same time interval, Simon Ingersoll had patented the first steam-powered, top hammer rock drill to provide higher productivity in blast hole drilling. It is well known that water, as an activating, flushing and cooling medium, has many significant advantages over the use of air. However, it was not until 1973 that top hammer systems (either air or hydraulically activated) for larger rigs were adapted to the use of water flush, typically via “under the head” swivels.The concept of a water-powered, down-the-hammer (WDTH) had been explored prior to G. Drill acquiring the original patent from Atlas Copco in 1988. LKAB, a huge underground mining company owned by the Swedish Government and providing about 90% of the European Union’s iron ore, purchased G. Drill in 1991 and encouraged the commercial development of the WDTH. The first full-scale WDTH production works were carried out for LKAB in 1995, since when over 25 million lineal meters of drilling have been recorded in both underground and surface applications.In 2001, G-Drill was renamed Wassara, which today still holds the worldwide patents for WDTH technology. Regarding North American usage, the first significant application was by Advanced Construction Techniques (ACT) Ltd. during the test grouting program conducted for the U.S. Army Corps of Engineers at McCook Reservoir, Chicago, in 2002. Since then, WDTH has become the tool of choice for specialty drilling and grouting contractors on dams and other major structures throughout the U.S."

Jan 1, 2015

By E. Ulrich Klotz

It is difficult to predict accurately the capacity of driven piles in sand. In practice, this uncer­tainty either leads to conservative designs if the capacity is under-predicted, or worse, if the capacity is over-predicted, it can lead to severe foundation problems. One significant possible cause of the problem is that currently available semi-empirical design methods do not capture the fundamental mechanisms that govern the load capacity of driven piles in sands. As part of a recent research project at City University centrifuge tests on a driven model pile in sands have been undertaken. A fully instrumented model pile was constructed and pushed into samples of quartz and carbonate sand thus covering a wide range of mineralogies. Tri-axial tests were used to determine the fundamental patterns of behavior of the sands. This allowed a general framework to be established, in which the in situ stress:volume relationship is shown to govern the capacity of the pile. The paper sets out with a brief introduction of the experimental techniques used in the study. The results of the pile tests are discussed in detail with particular attention given to distribution of the radial stresses along the pile shaft. Existing design methods for piles in sand are then discussed in the light of the new understanding gained from the research, highlighting their deficiencies and suggesting an improved approach.

Jan 1, 2002

By Lucien Weber

In the Shanghai area, the soil conditions are such that bearing piles have become an essential foundation part of the new highrise buildings. In order to reduce the settlements under the high working loads of about 2300 kN/pile, the Chinese building authorities require the pile tip to penetrate into the compact sand layer, situated at approx. 60-70 m depth. No H-piles have yet been tested under these conditions in Shanghai. This paper describes the driving of 8 H-bearing piles with 4 different shapes and with lengths varying from 45 to 75 m. Dynamic measurements are performed during driving and after a wait time of approx. 40 hours in order to assess the change in bearing capacity in function of time and in order to get an idea about the resistance distribution along the piles by using a stress wave analysis program (CAPWAP). One pile is equipped with channels between the flanges for executing verticality measurements with an inclinometer. However, this test has not yet been performed. One month after driving, two piles of 75 m length are statically loaded both in vertical and in horizontal directions.

Jan 1, 1987

By Nabil F. Ismael, Khalid Farraj

"The axial load transfer along large diameter bored piles in very dense silty sand was examined by field tests. Two instrumented piles 1.2 m diameter and with embedded length of 18 m and 25 m were load tested in axial compression to failure in connection with the construction of a big tower building in Kuwait City, Kuwait. Instrumentation included vibrating wire strain gages at various levels, displacement transducers and extensometers. The purpose being to measure the axial load distribution, skin friction, and base resistance at various load levels. In addition the settlement of the piles and the elastic compression were monitored. The ultimate pile capacity, side friction, and base resistance were determined and correlated with the Standard Penetration Resistance values as determined from the boreholes. Most of the load was transferred as side friction and the pile settlements at the maximum loads ranged from 1.6% to 2.2% of the pile diameter.INTRODUCTIONLarge diameter bored piles are used with increasing frequency for heavy structures in Kuwait and the Gulf region in calcareous sand. The behavior of short piles ranging in depth from 8 m to 15 m was examined by field test (Ismael 2012). However, larger diameter and deeper piles are being used more frequently, including the project described in this paper which included piles with 1.2 m diameter and 18 m to 25 m depth. The design of these piles requires knowledge of the skin friction and point resistance in these soils. While field tests on driven piles are available (Ismael 1989, Ismael 1999), field test data on long large diameter piles installed through very dense sands or silty sands are very limited at present. The results of two load tests carried out recently on instrumented bored piles at one site in downtown Kuwait City have become available. In these tests the failure load was extrapolated from the test results. It is important to examine and analyze the test results for the benefit of the geotechnical research and design engineers."

Jan 1, 2017

By Abolfazl Eslami, Fatemeh Rostami, Sara Heidarie Golafzani, Mohammad Arabameri

Collapsible loess is classified as problematic soil found in most continents. The loess immediately collapses under stresses induced by axial compressive loading or the soil weight when exposed to moisture. In Iran, vast areas of the Golestan province are covered with aeolian loess deposits. This paper investigates whether the simultaneous effect of inundation and pre-loading in helical pile installation are operative and effective in improvement of Golestan loess. The effect of installation conditions on loess collapsibility is studied via two main approaches, i.e., field investigations and physical modelling. The experimental studies include installation of eight single helix piles in the Amirkabir University of Technology Frustum Confining Vessel, i.e., FCV-AUT. Also, four single helix piles with embedment depth of 3 m and diameter of 250 mm were installed in Golestan province and full-scale pile static loading tests were performed. The results indicated that the simultaneous application of crowd loading and water pressure during installation of helical piles results in better soil shear strength parameters. Moreover, high crowd stresses or low crowd stresses accompanied by water pressure during pile installation brings about similar load-displacement behavior of model piles installed in FCV-AUT and full-scale helical piles.

Oct 1, 2022

By S. Narasimha Rao

Significant amounts of lateral load may act on pile foundations supporting structures such as transmission line towers, tall structures, bridge abutments, offshore platforms, quay wails, harbour structures and anchorages for water front structures. There were several theoretical and experimental studies conducted on laterally loaded piles in clays to determine ultimate lateral capacity and deflections under working loads. Under a lateral load, a pile deflects in the direction of load application and the soil in front of the pile offers resistance to this movement. The ultimate lateral resistance of a pile can be estimated considering the statics of the pile for a known distribution of soil resistance with depth. In this paper, considering the contributions from both lateral shear drag and frontal passive earth pressure, a method has been proposed to estimate the ultimate lateral capacity of rigid piles in clays. The lateral shear drag has been estimated in terms of adhesion and shape factor. A few load tests were conducted on model piles subjected to lateral loading and these experimental values are used in verifying the proposed method. The reported results obtained from both model tests and field tests were used in support of the predictions made. In all the cases, there is a good agreement between the predicted and measured capacities.

Jan 1, 1996

By Arash Maghsoudloo, Asli Can

"Abstract This paper presents a ground improvement implementation case under a raft foundation of a local hospital. The selected ground improvement method is Wet Soil Mixing (WSM) technique. Soil mixing is increasingly applied to environmental applications and ground stabilization in geotechnical projects. In this technique, weak soil is mixed with cementitious slurry to improve the characteristics of the soil. The investigated case is one of the pioneering WSM ground improvement technique implementation cases in Turkey. The soil profile is mainly consisted of low plasticity clay. The effect of ground improvement is verified by a series of laboratory tests and four in-situ pile loading tests. The results of in-situ pile load tests on constructed soilcrete columns showed an acceptable factor of safety for the bearing capacity of the WSM columns. Measured bearing capacities in all four tested columns were nearly 20% higher than calculated values. In addition, a set of samples are obtained from the constructed columns and unconfined compression tests have been conducted. The laboratory test results indicate that the selected cementitious slurry has a sufficient efficiency to form the stabilizing columns.IntroductionIn the construction industry, stabilization of the soft ground by lime or cement stabilization is a widely used technique. In ground improvement systems deep mixing method (DMM) results in the same stabilization in deep portions of the soft soil profile by mixing cementitious slurry by means of mechanical augers. The pioneering cases of modern deep mixing application can be traced back to the year 1970 that was used for the stabilization of marine soils below the water level for the construction of harbor structures (Terashi et al., 1979). Nowadays, DMM is shown to be a proper and efficient method for the foundation of the structures and embankments on land. Some recent studies also reported that reasonable settlement reduction range in the stabilized soils under the foundation of structures (Archeewa et al., 2011). In addition to reduction of the structural settlement under service loads, deep mixing methods are also utilized when there is a concern with contaminated soil and groundwater or groundwater control (Andromalos and Bahner, 2003).Although, the DMM is shown to be a successful method in numerous studies for improvement of a wide range of soil types such as organics, fine-grained, and coarse grained material, it has some limitations (Archeewa et al. 2011, Jameson et al. 2010, Jelisic and Leppanen 2004, Lambrechts and Roy 1997, Meyersohn 2007, Miki and Nozu 2004, Olsson et al. 2008, O’Rourke and McGinn 2004, Stewart et al. 2004, Yang et al. 2011). High soil density and stiffness could damage deep mixing rigs. Engineering properties of the soilcrete columns changes based on the soil type, water content and other factors such as organic content of the available soil profile, so properties of the generated soilcrete should be verified by a set of rigorous testing procedures (Puppala et al. 2004).Based on the general classifications presented in the ground improvement literature, deep soil mixing method is divided into two main types of dry or wet mixing methods. In the dry and mixing methods compressed air and water are utilized as the binder transporter medium respectively (Moseley and Krisch, 2004). In addition, DMM methods can be categorized based on the employed mixing methods during the construction. In this study, the main aim is to present and elaborate on the selected method is known as Wet Speed Soil Mixing (WSSM)."

Jan 1, 2014

By Subrata Ray

A large no of power stations are being set up in Chandrapur area having coal deposits. Several industries are also coning up in this area. The subsurface is geologically formed under Gondwana system and consists of shale strata at depths ranging from 8 to 12 m. The stress deformation characteristics of shale exhibits wide variation because of it's geological origin. In view of this, a study was conducted on bored cast in-situ piles installed for a Switch yard project to evaluate load settlement characteristics of three test piles to understand the probable engineering behaviour of the material at the tip and the sides. An approach is developed to simulate the load settlement behaviour as observed in the field, theoretically. This is based on the concept of load transfer. The fit is obtained by varying the parameters, thus may be considered as iterative in nature. The theoretical curves closely matched the observed curves. The results of this study are presented in this paper.

Jan 1, 1996

By Aly M. Mohammad

The design of large diameter drilled shafts in weathered rock has always presented a challenge to the foundation engineers. Degree of weathering and load transfer mechanism through the rock are essential elements required for the design. From the Contractor's perspective specifying the right equipment and estimating the rate of drilling in the weathered rock are key elements for successful construction. The Delaware River Tramway Project has provided an opportunity to address the design and construction of drilled shafts in weathered rock. The Tramway, supported by twin 300-foot towers, will shuttle eight-person gondolas across the Delaware River in about four minutes. Each tower, founded on four high capacity drilled shafts, is designed to resist large axial and lateral loads. At the New Jersey tower, each 7-foot diameter shaft extends 145 feet deep and terminates in weathered Mica Schist. The shafts are situated in the Delaware River where the mud line is approximately 20 feet below Mean Low Water. Below the mud line, there exists a very soft, 20-foot thick layer of organic silt, followed by a 40-foot thick dense sand stratum. Below these sand and silt strata, a 70-foot thick layer of weathered Mica Schist underlies the entire site. Both skin friction and end bearing in the weathered rock stratum were utilized in the analysis to compute the axial capacity. AASHTO and the PennDOT design methodologies were utilized independently during design of the drilled shafts to verify the design. The drilling of large diameter drilled shafts embedded into weathered rock and situated in a marine environment provided a unique challenge in the construction. A permanent steel casing was installed for a specified depth and proper equipment was used to drill and keep the shaft open through the weathered rock. In addition, a 5000 kip Osterberg load test was performed on one shaft to verify design assumptions and confirm the shaft capacity. The results of the test were utilized to establish load transfer characteristics within the weathered rock and to develop foundation design parameters to be used for the remaining shafts.

Jan 1, 2003

By Daniel W. Mageau, Larry W. Applegate, Aaron K. McCain

"An innovative method of ground freezing was successfully tested to create a “dry” excavation condition for a new building foundation at a site in downtown, Miami, Florida. The subsurface conditions in Miami generally consist of very porous, weak limestone and sand with groundwater near the surface. Water flow through these materials can be very high. Dewatering is extremely restricted in Miami so deep below-grade structures are rare and expensive. A new, innovative method to allow deep excavations in dry conditions without dewatering involves the creation of a thick, temporary, frozen soil plug below the planned excavation depth across the entire site to cut off vertical groundwater flow during construction. Frozen soil is impermeable and very strong and has long been used for temporary structural and water-tight shored walls. Using the same proven principals, frozen soil plugs are very effective at cutting off water from the bottom of the excavation as well as resisting upward buoyant forces. This new freezing method can be used for fairly deep excavations in new building construction supported on deep foundations. The building piles act as temporary anchors for the frozen plug to resist very high upward buoyant pressures until the permanent structural slab is completed.IntroductionUnlike other Cities, below grade basements are rare in Miami. The few basement foundations constructed have utilized a cumbersome and expensive method of excavation and shoring involving underwater excavation, tremie slabs, and commercial divers. The key issue for underground construction in this area of the country is the vertical flow of groundwater through the base of the excavation. To deal with this issue in the past, the contractor first installed all of the building piles and the perimeter shoring walls. Then, interior sheet pile walls are installed to create small manageable excavation pits. Each pit is then excavated through standing water “in-the-blind” and around the buildings support piles. The final excavation, interior struts, and inspection is performed by commercial divers. Finally a thick foundation tremie slab is poured under water. This method could be successful but proved to be time consuming and expensive. In addition, some building piles were occasionally damaged during the under-water construction process."

Jan 1, 2015

By Z. C. Chen

Based on the analysis of load test data of long floating piles in soft soil regions, the expressions of load-transfer function of pile shaft and tip for soft soils are presented in this paper, and the data of cone penetration test are suggested to use for calculating the parameters of load-transfer functions. For the loads of pile within the range of the working load of pile, the estimated pile stiffness by the suggested method in this paper are in satisfactory agreement with the results of load tests. The current Vijayvergiya's method and Satowa's method also are used to calculate pile stiffness in soft soil for comparison.

Jan 1, 2010

By Mohammed Sakr

The use of helical piles for permanent foundation applications has become a practical and feasible alternative to the traditional cast-in-place concrete or driven steel piles. Research and development, installation equipment and manufacturing improvements in the helical piling industry have led to this trend. Moreover helical piles are typically smaller in size and weigh less than traditional piles, and require relatively smaller equipment and therefore it is a cost effective option. The latter is a very attractive feature for foundations installed in remote sites across Alaska. This paper presents full-scale pile load test results of helical piles and driven steel pipe piles installed in a site located in Anchorage, Alaska. Four full-scale pile load tests were carried out including two axial compression and two uplift load tests. Both helical piles and driven steel pipe piles were installed and tested at the same site under similar conditions to provide a direct comparison. The results of the full-scale load tests indicate the superior performance of helical piles compared to driven steel pipe piles. This paper describes the pile installation and test setup, presents the test data, and discusses the results.

Jan 1, 2009

By A. Daouadji, P. Cazes, S. Grange, L. Briançon, R. Milane

Construction in congested urban areas is often accompanied by geotechnical problems due to high loads and the impact caused by nearby buildings. For this reason, it is important to understand the behavior of the soil and the structure without forgetting the essential role of the interaction between them. Experiments, instrumentation and numerical modeling are the main methods used to study this behavior. To this end, pressure cell, strain gages, vibrating wire extensometers and optical fiber sensors are installed on the reinforcement steel of pile and raft foundations to monitor stresses and induced deformation in these elements during and after construction. A fiberglass rod extensometer is placed in the soil to help measuring the displacement due to excess loading, knowing that the pile foundations are embedded in the Rhône’s alluviums and reach the molasse, a particular and challenging soil with properties that are not yet well understood. The objective of this paper is to present the geotechnical instrumentation program carried out for the tower Silex2 in Lyon, France, and to describe the types of sensors used and their installation on site. INTRODUCTION The complexity of geotechnical structures like dams, bridges or high-rise buildings requires a sound understanding of the behavior of the soil, the structure itself and the interface. Therefore, a geotechnical instrumentation program can be essential in many ways. During the site investigation stage, it can help determine the initial conditions experienced by the soil in the field by measuring parameters such as the compressibility index or the permeability. During the construction stage, real time measurements can protect the structure from premature failure, help validate and optimize the design if needed. In addition, sensors measuring pore-water pressure, loads, deformations and settlements allow for monitoring the performance of the structure. This is called the observational method. Finally, during the operating phase, instrumentation aims to study the long-term behavior of the structure (Nicholson et al., 1999).

Jan 1, 2019

By Zia Zafir

"Levees in the central valley of California are primarily for flood control purposes and thus are subjected to infrequent hydraulic loading. The primary concern for these levees is their instability due to through and under seepage. Primary seepage control measures are seepage cutoff walls and/or seepage berms. The cutoff walls primarily consist of soil-bentonite (SB) slurry walls. The seepage berm could be a drainage blanket to allow the seepage with controlled exit gradient or an impervious layer to provide enough cover to protect any adverse effects of seepage in terms of sand boils. Although, Sacramento is an area of moderate seismic activity, levees protecting urban areas require assessment for the potential instability due to liquefaction and associated vertical and lateral deformations. In certain cases, the seismic deformations of the levee may not compromise the stability of the levees, but they may cause damage to the seepage control measures. Depending on the nature and extent of the damage, the mitigation measures may require limited or full replacement of the seepage control measures. This paper will provide a systematic assessment of these different types of seepage control measures under vertical and lateral deformations due to liquefaction and lateral spreading under seismic loadings.INTRODUCTIONThere are two broad categories of levees in Central California: levees that are subjected to continuous hydraulic loading such as delta levees and are called frequently loaded levees (FLL) and flood control levees that are subjected to seasonal or infrequent hydraulic loading, called infrequently loaded levees (ILL). This paper will focus on the seismic response of ILL. The probability of ILL experiencing an earthquake at the time of the design flood is very low. Therefore, consequences of seismic failure of flood control levees are only significant in terms of response time required to restore the level of flood protection provided by the levee before the next flood season. An example for this restoration is the restoration of the Pajaro River levees in Santa Cruz, California after the 1989 Loma Prieta Earthquake. Nevertheless, failure of flood control levees due to a seismic event could result in loss of the entire levee and/or loss of freeboard. In addition, some of the seismic failure of ILL levees may result in loss of seepage control measures such as the soil-bentonite wall.The State of California State approved Senate Bill (SB) 5 in 2007 that mandates for 200-year flood protection to be the minimum level of protection for urban and urbanizing areas in Central California (Sacramento-San Joaquin Valley) by the year 2025. This legislation also requires that urban and urbanizing areas protected by Federal project levees cannot use adequate progress as a condition to approve development after 2025. SB 5 requires that the urban level of flood protection be consistent with criteria used or developed by DWR (Government Code § 65007(k)). To avoid delaying urgently needed flood protection, Urban Levee Design Criteria (ULDC, 2012) was developed."

Jan 1, 2016