Search Documents

By Rich A. Lamb, Paul J. Axtell, Michael K. Muchard

"Since 2010, the Minnesota Department of Transportation (MnDOT) has performed eight full-scale compressive load tests on large-diameter pipe piles at four different project locations across the state. All of the piles were 42-in diameter, open-ended pipes driven to practical refusal on sedimentary bedrock with D125-32 diesel hammers from three separate manufacturers. The rapid load test method in general accordance with ASTM D7383-10 (Statnamic method) was used along with high-strain dynamic testing and subsequent signal matching. Results of these tests indicate that the axial nominal resistance of these piles in compression is not controlled by geotechnical considerations when driven with an appropriately sized hammer and installation criterion. Rather, the predominantly elastic load-deflection behavior of the piles under compressive load suggests the axial nominal compressive resistance is controlled by the structural capacity of the pile. In all instances, the rapid load tests indicated a nominal resistance exceeding that produced by high-strain dynamic tests due to insufficient hammer energy to fully mobilize resistance. In all cases, the hammers used were able to easily install the piles through the soil overburden. Mobilizing a larger hammer simply to demonstrate high-strain dynamic resistance is not economical or practical. This paper presents the subsurface conditions at each location, the ensuing test results, and the ramifications for future projects in Minnesota utilizing large-diameter open-ended pipe piles.INTRODUCTIONThe Minnesota Department of Transportation (MnDOT) has recently performed eight full-scale compressive load tests on large-diameter pipe piles at four different project locations across the state. The four project locations described in this paper where pile load testing was performed are shown in Figure 1 and exist in the southeastern portion of Minnesota. The projects are all major bridges crossing the Mississippi River in three instances and the St. Croix River just above the Mississippi River in the other instance. The first project is the TH 61 Mississippi River crossing in Hasting, MN where two load tests were conducted. The second is the TH 36 St. Croix River crossing in Stillwater, MN where two load tests were performed. The third project is the I-90 Mississippi River crossing in Dresbach, MN where three load tests were conducted. The final project is the TH 43 Mississippi River crossing in Winona, MN where one load test was performed."

Jan 1, 2017

By Michael G. Batten, Brian D. Keaney

]The Virginia Department of Transportation (VDOT) and the harbors on the James River routinely use precast concrete piles founded in the Yorktown formation to support bridges and other coastal structures. However, axial pile resistances for large diameter piles in this area have been historically overestimated on past projects. This may be due to a common assumption that very large unit end bearing resistance will be developed for a large diameter displacement pile that is driven a significant depth. This assumption is integrated in the Nordlund (1963; 1979) method which is commonly used to estimate axial pile resistance for bridge foundations. A static and dynamic pile load testing program was implemented as part of the Hampton Roads Bridge and Tunnel Expansion project in Norfolk, VA in the James River. A primary objective of this program was to calibrate an axial resistance calculation method against the measured load test results. A method developed by Eslami and Fellenius (1997) that uses CPTu data directly was effective at calibrating to the measured load test results, and allowed for clearer interpretation of the unit resistance values than indirect, semi-empirical methods that require interpretation of soil friction angle and undrained shear strength.

Sep 8, 2021

By Akhila Manne, Prasad P. V S R

Storage tanks are heavily loaded thin-shelled structures that exert large loads on and require large foundations to support them. They are generally very sensitive to foundation settlements as it may hinder the performance of tanks resulting in significant commercial or social impacts. Selection of their foundation is dependent on availability of suitable ground and limitations imposed by design specifications. Design of the tank foundations is generally based on theoretical methods and validation by representative field tests. This paper reviews settlement criteria for storage tanks as per national and international standards, case studies of large to medium diameter tanks supported on deep foundation i.e., bored cast-in-situ piles and shallow foundations on improved ground and their performance during load tests & hydro-tests is discussed. Paper concludes that storage tanks can also be supported on shallow foundations resting on improved ground reducing the settlement, time and cost significantly depending on the sub-soil.

Nov 1, 2022

By Karen Talbot, Noah Maier, Rob Jameson, Giuseppe Gaspari

A storage and drainage tunnel advancing below I-75 in Detroit, Michigan experienced sudden subsidence. The Tunnel Boring Machine (TBM) was damaged to the extent that its shield, cutting head and extensive interior components needed to be extracted and replaced along with several completed tunnel segments. The tunnel was 16 feet (4.9m) in diameter with crown over 79 feet (24m) deep at the time. The tunneling contractor immediately engaged their designers and specialty subcontractors to develop a scheme to access the machine and repair the tunnel. They required a shaft 99 feet (30m) deep, with unobstructed plan dimension of 50 feet (15m) to accommodate the large components that needed to be removed and replaced. This precluded the application of an internally braced excavation and instead earth support solutions focused on use of a compression ring. Since the completed tunnel section behind the TBM obstructed closure of the compression ring below its invert, this paper describes the innovative access shaft solution employed. A conventional compression ring was constructed using 5 feet (1.5m) diameter drilled shafts down to the tunnel crown. In front of, and to the sides of the tunnel heading, the secant shafts were extended to over 150 feet (46m) depth, creating a horseshoe of support extending 50 feet (15m) below the planned excavation invert. Larger diameter "King Pile" shafts were drilled immediately to either side of the tunnel, overlapped into each end of the secant "horseshoe". The king pile shafts, together with a heavily reinforced ring beam above the crown elevation, acted as a door frame to transfer hoop loads from the incomplete secant arc into reaction supports above and below the tunnel. These oversize king pile shafts were extended and socketed into rock over 70 feet (21m) below tunnel invert. Very tight installation tolerances were necessary to maintain secant shaft alignment to depths exceeding 150 feet (46m). The project operational, geotechnical, and quality data was managed and visualized using a custom GIS interface. This paper will present the design approach employed and review the construction and quality program selected to repair the tunnel.

Oct 1, 2022

By Beim Jorge, Piscsalko George

"Verifying the quality of cast-in-place foundation applications, particularly those cast under slurry, is of course important, due to its great dependency on the methodology employed and on the practices of the site personnel. Due to the techniques used to install these elements, it is usually not possible to inspect the hole prior to grout or concrete placement, but there are several Non Destructive Test (NDT) methods available to assess the integrity of the completed foundation elements. This paper will compare several NDT methods with the Thermal Integrity Profiling (TIP) method for verifying the integrity in Continuous Flight Auger (CFA) piles and Bored Piles. The Thermal Integrity Profiling method will be described and some examples will be presented where TIP testing was used to confirm the structural integrity of CFA piles and Bored Piles.IntroductionThere are several Non Destructive Test (NDT) methods available for integrity testing of foundation elements. Each of those methods has advantages and disadvantages (White et al, 2008). Some methods test the integrity based on the reflections of a stress-wave generated by low or high-strain impact, while others require tubes to be installed prior to concrete pouring, and test the integrity between those tubes, or within a small proximity of them. The former methods (especially the low-strain) are faster and more cost-effective, but are not able to detect the quadrant where the damage is located. The latter methods are able to determine the quadrant, but do not test the region outside of the reinforcing cage, that is, they are not able to determine the concrete cover. The Thermal Integrity Profiling (TIP) NDT method overcomes the limitations of these other NDT methods.Overview of Shaft Integrity MethodsUntil now, the most widely used methods to test the integrity of Bored and CFA piles were the low-strain pile integrity testing and the cross-hole ultra-sonic testing. The low-strain method for integrity testing (PIT) involves attaching an accelerometer usually to the pile top (using a putty or wax) and striking the pile surface with a handheld hammer, which causes a compressive wave to enter the pile. This wave is totally reflected when it reaches the end of the pile or a major defect, and is partially reflected when it encounters any change in crosssection, or a change in the resistance or density of the pile material. These reflections arrive at the top at a time determined by the distance and wave speed, and causes a noticeable change in the signal detected by the accelerometer. The acceleration signal is normally converted to velocity by simple integration, and sometimes the force applied by the hammer is also measured. The velocity (and force) signals can be processed by the pulse-echo method (in the time domain) or by the transient response method (in the frequency domain)."

Jan 1, 2015

By Ashraf M. Eid

Most research dealing with the problem of laterally loaded piles has been the response of individual piles subjected to lateral loads and/or bending moments. However, piles are seldom used individually but are normally constructed in clusters or groups. Little information is available of the effect of pile-soil-pile interaction (PSPI) on the performance of the group. This may be attributed to the difficulty of carrying out full-scale tests. Such tests are prohibitively expensive and require special installations to provide the required large lateral loads. The problem of laterally loaded single piles or pile groups involves the complexity of extending the theoretical solutions to the limits where the actual soil behaves nonlinearly. As the load increases, the elastic soil behavior cannot be adopted for design. Nonlinear soil behavior or the elasto-plastic behavior is evident. This research consists of experimental and theoretical models. The experimental work was conducted on models of free head pile groups in different configurations. The piles were in a sand formation and compared to the behavior of a single pile. The possible factors that influence the group behavior could be visualized. The experimental data was also compared to the widely used theoretical approaches to determine their adequacy. The analytical model makes use of the finite difference approach to calculate the soil non-linearity. A new approach equates the measured ground deflection and maximum bending moments of each row at every load level with the analytical model of single pile. This is the Deflection-Moment Fitting (DMF). The most suitable non-linear soil modulus modes and row contributions could thus be determined. Design of pile groups can be based on data pertaining to soil characteristics of the single pile. Results of the analysis were consistent with other approaches and proved to be adequate for design.

Jan 1, 2005

By Jean Wehbe, Daniel C. Brahana

"The new Mercedes-Benz Stadium (MBS), home of the Atlanta Falcons, is part of a new era of stadium construction in the U.S. These new-age stadiums are larger and have more amenities than their predecessors. Many of the MBS’s features, including its innovative retractable roof, result in extraordinary structural loads. The roof structure is supported by a series of mega columns that bear on eight large caps, six of which are supported by drilled piers. Each of the pier caps contains between 8 and 16 drilled piers that bear in the underlying bedrock. The design pier diameters are 6 and 6.5 ft (1.8 m and 1.9 m). Augercast piles were used to support two of the mega column caps. Drilled piers, augercast piles, aggregate piers and spread footings were used to support the more lightly loaded portions of the structure.The focus of this article is the construction aspects of the drilled pier foundations. Initially, a fairly extensive drilled pier load test program was performed. Load testing included a Statnamic compression test, two Osterberg Cell tests and two lateral tests. Production pier installation included over 3,800 linear ft (1,158.2 m) of earth excavation and over 1,350 linear ft (411.4 m) of hard rock excavation. The piers contain more than 6,600 cu yd (4,587.3 cu m) of concrete and 1,100 tons (998 tonnes) of reinforcing steel. Drilled pier installation took about 4.5 months. ABE Enterprises was the specialty foundation subcontractor and Bauer-Pileco was the equipment provider.Site and Subsurface ConditionsThe project site is in downtown Atlanta and was originally occupied by residential buildings. A portion of the site was later developed as a rail yard, and other areas contained light manufacturing, warehouses and other relatively light structures. For the past 15 to 20 years the site had been used for surface parking.Beneath a surficial layer of manmade fill, soil test borings at the site generally encountered residual soil, partially weathered rock and the parent bedrock. The bedrock at the site is highly variable, both in elevation and in hardness/quality. The depth to rock is reasonably uniform within the western two-thirds of the site at about 20 to 50 ft (6 to 15.2 m), with a few exceptions. In the eastern third of the site, the rock drops off dramatically to the north and east. In one mega column cap, there was almost 80 ft (24.3 m) in elevation difference. In two borings in the cap that were 20 ft (6.1 m) apart, the top of rock varied in elevation by 34 ft (10.3 m)"

Jan 1, 2016

By Bengt H. Fellenius

It is a truism that in the design of pile foundations one must consider both capacity and settlement. As to capacity, most basic text books contain simple methods of design of capacity of single pile. More sophisticated methods are the subject of many journal papers. However, methods for design considering settlement of pile foundations are scarce. (Most confuse settlement with the movement due to load-transfer?the transfer of load from the pile to the soil). Furthermore, for both capacity and settlement, most methods include several simplifying assumptions regarding soil layering and neglect the effect of the frequently occurring fill and excavations, as well as changes of the groundwater table and pore pressure distribution. Therefore, the methods may provide qualitative results, but not quantitative. Because of this situation, pile design often appears as somewhat of a guessing game and a very subjective?and risky?occupation. This need not be. Pile foundation design is controlled by three factors: capacity, strength, and settlement requirements and these have been combined in a method called "the unified design of piles and pile groups considering capacity, settlement, and negative skin friction" (Fellenius, 1984; 1989), which method is summarized in this guide.

Jan 1, 1991

By Cassandra A. Wetzel

"Rock socketed mini-piles are a desirable foundation alternative when design capacity is more than 40 tons and there is limited access. In this case history mini-piles were designed to support between 75 and 200 kips at 12 locations adjacent to a perimeter wall, a party wall and at cast iron column piers. Limited geotechnical information, low overhead clearance, and active building population tested the creativity of the team to get the piles installed. The key geotechnical concern during installation of the mini-piles was the presence of a glacial till layer above the bedrock surface that restricted the seating of the casing into bedrock with a track mounted drill rig. Soil loss during the advancement of the rock socket using an air hammer was excessive and increased the risk of subsidence. Over a three week period the engineer worked with the contractor to modify the design, means, methods, and materials to install piles with adequate load capacity. This paper will present the changes in design and construction methods that were required.INTRODUCTIONRock-socketed mini-piles are a common and desirable deep foundation alternative to support loads more than 40 tons in New York City. Limited vertical clearance, accessibility, vibration control, and load capacity make this pile type attractive; it also does not require a static axial load test when socketed into rock. This added benefit makes this alternative all the more feasible.The installation of a drilled pipe extending to bedrock through a glacial till deposit presented challenges to the contractor and engineers to confirm the casing is seated sufficiently into the rock prior to drilling the rock socket. The loss of soil between the steel pipe and the till/bedrock interface can compromise the performance of the pile and soil loss can result in settlement of the ground surface.This paper presents the design and construction method changes made on one project during the installation of ten limited access rock socketed mini-piles."

Jan 1, 2017

By Chandramohan P. V., Ravi Kishore

"An underground reservoir was to be constructed at Doha in Qatar. Simsima lime stone is present at the bottom. When the reservoir is empty, there will be uplift at the bottom but this will change to downward load when it is full. The rock at the bottom had high bearing capacity to resist downward load. But uplift had to be resisted by piles or anchors. The reservoir has a size of 120mx80m. Shrinkage and creep of concrete coupled with thermal contraction imposed a horizontal movement of 26mm on the extreme piles. So, piles have to accommodate this as well. This unique situation needed a unique solution. The solution was to provide piles with flexible high tensile strands to take tension. An annular space near the head of the pile would facilitate horizontal movement as well. Compression load was directly passed on to the raft bearing on rock.INTRODUCTIONAn underground reservoir for storage of drinking water was to be constructed at Doha, Qatar. The reservoir was proposed to have a plan size of 120m x 80m. Clear height inside the reservoir was proposed as 17.2m, from the bottom of roof to the top of bottom raft. Overall height of the reservoir at the outlet from the top of the roof to the bottom of raft was to be 21.2m. For the sake of inspection and in order to prevent pollution from the surroundings a gallery was planned around the reservoir. This could accommodate pipelines as well. This gallery was 3.0m wide on three sides and 8.4m wide on the outlet side.The gallery had removable gratings as cover in order to facilitate maintenance. Capacity of the reservoirwas proposed to be 40million gallons. The reservoir is divided into four compartments with baffle walls in each one for water circulation. Roof of the reservoir is kept at 300mm above ground level. There are two levels of car park on top of the reservoir. Top of the reservoir roof is at +14.35. Bottom varies from - 6.68 to -7.08. Lowest water table is at +6.00. Concrete structure of the reservoir was designed by a local consultant. The Navayuga Engineering Company was entrusted with the construction. Please see Figs 1 and 2."

Jan 1, 2017

By Frank Haehnig

Ground freezing is a technique which is used more and more in tunnelling under complex ground conditions. This paper will present three case studies which highlight different aspects of the ground freezing technique when applied in urban environment. The first project is the City-Tunnel in Leipzig, Germany, which is being built beneath the central station and which is the largest ground freezing project currently under construction in Germany. The second case study is part of the North-South-Line project in Amsterdam, Netherlands where ground freezing will be carried out to al-low the TBM drive through old wooden foundation piles. The freeze tubes for this project will be driven using Horizontal Directional Drilling (HDD). The last project is the Hallandsas Tunnel Sweden where the ground freezing equipment has to be installed against high water pressure. The paper illustrates that ground freezing can be implemented in difficult ground conditions such as soft ground, highly fractured rock and high water pressure. The case studies highlight the importance of good workmanship. With the increasing numbers of large tunnels being constructed in difficult ground conditions the paper concludes that the complex case studies presented will be-come more representative for future tunnel projects in urban environments.

Jan 1, 2008

By A. J. Partos

Table 4, Page 311 Table 4 Experimental Parameters from Straight Line Interpretation of Mohr Failure Envelope [ ]

Jan 1, 1991

By Babak Mamaqani

The Regional Connector Transit Corridor (RCC) is the Los Angeles Metro area's ambitious light rail project, running under the city's main thoroughfares, Flower and 2nd streets. When com- pleted, it will alleviate traffic and parking congestion downtown, while connecting thousands of residents living in the bedroom communities of Inland Empire and Long Beach to their jobs there. The rail line of 1.9 mi (3 km), which involves a $1.756 billion (€1.545 billion) budget to construct the under- ground rail line, including three new stations. They are the Grand Av Arts/Bunker Hill station at 2nd and Hope streets, Historic Broadway Station at 2nd Street and Broadway, and Little Tokyo/Arts District Station at 1st Street and Central Avenue, which will offer riders their first "one seat/one fare" ride option from Azuza to Long Beach. Regional Connector Constructors JV is led by Skanska USA Civil West California District Inc. (Skanska), in partnership with Traylor Bros., Inc. (Traylor), to deliver RCC to the Los Angeles County Metropolitan Trans- portation Authority (Metro). PB&A was the structural engineer of record (SEOR) responsible to design the shoring systems for the Grand Av Arts/Bunker Hill Station at 2nd and Hope streets, and Historic Broadway Station at 2nd Street and Broadway. The temporary shoring design for Historic Broadway Station is the focus of this article, and why the project received special recognition as a runner up for DFI's 2021 Outstanding Project Award. Two main challenges are discussed in particular: design of the shoring system considering all construction stages, and design of an underpinning system where the Los Angeles Times Building (Times Building) protruded into the station footprint.

Apr 1, 2022

By Andy Boeckmann

In early 2021, DFI formed a Foundation Reuse Task Force due to concurrent and coincidental discussions of this topic during meetings of the Subsurface Char- acterization for Deep Foundations and Testing and Evaluation committees. Interested members from both commit- tees, as well as of the Sustainability Com- mittee, joined forces to form the task force. The task force mission is to promote foundation reuse by leveraging experi- ence among DFI members and collabo- rating across pertinent committees. General goals of the task force are to identify, assess and reduce risks associated with reuse; to educate owners and decision-makers about reuse; and to improve the investigation, design, construction and testing practices associated with reuse. One of the first orders of business for the task force was to organize a roundtable discussion of foundation reuse for DFI's 46th Annual Conference on Deep Foundations in Las Vegas. Last fall's discussion was framed as a continuation of the successful "Horses for Courses" session of SuperPile '21, which also focused on foundation reuse. However, whereas the SuperPile session focused on technical content, the annual conference panel on October 13, 2021, was envisioned as a less technical conversation that emphasized audience participation while addressing approaches to decisions about foundation reuse issues. The roundtable consisted of five panelists: • • • Bryan Hartnagel, Ph.D., state bridge engineer, Missouri DOT (MODOT) Tom Bradley, project director, Stanhope, London Hilary Shields, senior geotechnical engineer, Arup, London Jim Mackey, vice president/chief marketing officer, McGee Group, London Susan White, attorney, Benesch, Cleveland The roundtable was moderated by Andy Boeckmann, Ph.D., P.E., a senior engineer who works in Dan Brown and Associates' Missouri and Illinois offices, and is an article co-author.

Feb 1, 2022

By V K. Panwar, Sampat Raj

At a Fertilizer plant located in the southern part of India, 74 numbers of pump foundations have shown non-uniform settlements causing the tilting of pump foundations under self-weight primarily due to the presence of varying thickness of the heterogeneous subsoil beneath the pump foundations and soil erosion because of water seepage through deeper excavations in the close vicinity. Various corrective measures have been explored and taking due cognizance of the prevailing subsoil conditions, site constraints, and constructability aspects, micropiling has been adopted. This paper presents the site problem and details of remedial measures adopted for rehabilitation of the distressed pump foundations. The main objective of this paper is to provide guidelines for designer during design and detail engineering stage to avoid similar nature of problems and also to provide a solution concept to tackle similar nature of problem(s) if encountered at site.

Nov 1, 2022

By Rob Jameson

Micropiles are ideally suited to seismic retrofit applications. Their high tensile and compressive capacity can sustain the large concentrated loads induced during seismic events. Micropiles can be drilled through and grouted into the wide variety of soil and rock materials encountered in seismically active zones, using equipment that operates effectively within existing structures. Micropiles have seen increased acceptance and are now widely specified for retrofit work in the San Francisco Bay Area. While installation equipment and the structural configuration of micropiles have been largely unchanged since the early 1990?s, market forces have pressured both engineers and contractors to continually optimize the cost and performance of seismic upgrades. Instead of the contractor simply developing stronger, stiffer and cheaper micropiles as isolated structural elements in response to a specification, focus has shifted to maximizing the efficiency of micropiles within the overall foundation system. The case history of seismic retrofit project in Berkeley, CA is presented to illustrate the collaboration between designers and drilling specialist which resulted in a structurally efficient and cost effective design. The seismic retrofit program for this 6-story concrete building was developed through careful consideration of the geotechnical and structural mechanisms of resistance, in combination with the deformation response of high capacity micropiles (2670 kN) under ultimate loading conditions. This case history describes the interactive project development emphasizing performance-based design and field testing to optimize the micropile foundations and the overall structural system.

Jan 1, 2008

Abouleid,A.F.327 Ajdic, I.451 Albert, L.F. 221,307 Alem, A. 525 Asama, T. 431 Avgherinos, P. J. 373 Baker Jr, C.N. 331 Balossi Restelli, A. 171 Beckwith,G.H.33 Bellini, A. 469 Bermingham, P. 481 Bertero,M. 171,535 Beyer, M. 503 Bottiau, M.41 Botto, G. 205 Bruskeland, O. 337 Budhu, M. 349 Bullivant, R.A. 181 Bustamante, M.G. 185, 475, 535

Jan 1, 1994

By Andrzej Tejchman

A method of improvement of a subsoil under bored pile base by injection is presented. The method employs a special chamber attached to the reinforcement at the bottom of the drilled borehole. The chamber is made of semi-permeable textile bag. The injection entered under high pressure into the bag, causes prestressing of subsoil under the pile base. The results of load tests of piles improved in this manner have shown a substantial increase of their capacity together with simultaneous reduction of settlements. This technology has been implemented for four constructions such as trestle bridges in Gdynia and Warszawa and the bridges in Szczecin and Gdansk. The injection effects are shown based on the load test results.

Jan 1, 2002

By J. Hamada, K. Yamashita, Y. Shigeno, T. Tanikawa

"This paper offers a case history of piled raft foundation in soft ground supporting a twelve-story building in Tokyo. To increase bearing capacity of the soft soil as well as a countermeasure of liquefaction, grid-form deep cement mixing walls (DMWs) were employed with the piled raft. Based on the long-term monitoring results, the ratio of the load carried by the DMWs to the effective structure load after the construction of the raft was estimated to be 0.3 while that carried by the piles was 0.7. In order to clarify the contribution of the DMWs to bearing the structure load, numerical simulation of the settlement and the load sharing among the piles, the DMWs and the unstabilized soil was performed using a three-dimensional finite element model. The results of the numerical simulation agreed well with the measured values, when the Young’s modulus of the DMWs obtained from the unconfined compressive tests was adopted and the shear modulus of the soft soil was reduced to 50% of that at small strains.INTRODUCTIONIn recent years, piled raft foundations have been used in many countries as building foundations. The effectiveness of piled rafts in reducing average and differential settlements has been confirmed not only on favorable ground conditions as shown by Katzenbach et al. (2000), Poulos (2001) and Mandolini et al. (2005), but also on unfavorable ground conditions such as soft clay and/or liquefiable sand using ground improvement technique (Yamashita et al., 2011a; Yamashita et al., 2011b; Yamashita et al. 2013). Grid type ground improvement using the Deep Mixing Method has been applied to sandy ground as a countermeasure of liquefaction to increase liquefaction resistance of unstabilized soil left in the grid walls where its shear deformation during seismic motion is reduced by the confinement effect of the grid walls (Kitazume, 2013). The high applicability of the method was demonstrated in the 1995 Hyogoken-Nambu earthquake and the 2011 off the Pacific coast of Tohoku Earthquake (Tokimatsu et al., 1996; Uchida et al., 2012a; Uchida et al., 2012b).This paper offers a case history of piled raft foundation in soft ground supporting a twelve-story building in Tokyo. To increase bearing capacity of the soft soil as well as a countermeasure of liquefaction, grid-form deep cement mixing walls (DMWs) were employed with the piled raft. First, the results of long-term field monitoring on the settlement and the load sharing among the piles, the DMWs and the unstabilized soil are briefly described. Next, to clarify the contribution of the DMWs to bearing the structure load, the foundation behavior is simulated using a three-dimensional finite element model, and then the results of the numerical simulation are discussed."

Jan 1, 2015

By Clayton A. Signor

Abstract: Expansive soils cause more damage to structures annually than a combination of other major natural disasters. Because of the cost to our society, all means and methods need to be fully explored to mitigate the problems associated with expansive soils. This study will present a foundation design approach that is underutilized in this application, driven piles. The main objective of the study is to present pile test results and analysis from four driven pile project sites in three types of expansive soils found in central Texas: Del Rio formation, Taylor/Navarro formation, and expansive alluvium. High strain dynamic pile tests were conducted on each of the four studies with rigorous signal matching analysis from the CAse Pile Wave Analysis Program (CAPWAP). Ultimate pile capacities ranged from 73 to 311 kips with an average of 61% of the total capacity coming from the pile shaft and were two to six times the structural capacity needed. Allowable loads calculated from Modified Gates dynamic formula best modeled allowable test results. Average unit skin frictions ranged from 0.50 to 4.71 ksf. Restrike pile tests of 1 to 17 days after initial driving reported 30 to 100% shaft capacity gain. All open-ended pipe piles driven produced soil plugs ranging from 4 to 14 feet thick. Small diameter, thick-walled, open-ended pipe piles reached penetration of twice the depth of designated zone of seasonal moisture change without problem. The observed production rate of the driven piles was on average 8 minutes, which implied daily production of 15 to 40 piles. Predrills or augered holes should be specified for underground obstructions found in soil investigation.