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By J. M. Pei

In this paper, the nonlinear finite element analysis is used to study the support system of a tunnel which is designed to pass through deep-embeded stratum. The rock mass is rather intact, though a section of tunnel will pass through the weak belt. Under the influence of the high ground stress, the condition of stability and the form of support become complicate. This paper, talcing into account the nonlinear properties of rock mass and the Interaction between rock, and support, makes a comparison between the two kinds of soft and rigid support systems, and analysed the changes of their bearing forces.

Jan 1, 2010

By Jørn H. Thomsen

This paper presents the experience gained and the lessons learned over the last decade within the numerous offshore foundation projects undertaken in the offshore waters of Denmark and Belgium by COWI A/S of Denmark. This experience derives from the close collaboration with, and interaction between the owners, contractors, and engineers in the various stages of project development. In turn, the experience draws on COWI's experience within foundation of large bridges world wide over half a century. Focus is on two pioneering gravity base foundation projects: ? Nysted in Denmark, currently the largest offshore windfarm worldwide with 72 Nos Bonus 2.3 MW turbines in water depths up to 10 m in the relatively benign inner Danish waters ? Thornton Bank in Belgium, where the first phase - comprising 6 Nos REpower 5MW-turbines of a total of 60 - are planned to be built in the rough North Sea in water depths exceeding 25 m.

Jan 1, 2013

By Thomas C. Anderson

Tiedback walls are now recognized and accepted as a good solution for a variety of structural problems: ? Retaining Walls and Bridge Abutments in cut situations ? Landslide stabilization ? Repair/support of existing walls Acceptable techniques have been developed for anchoring in cohesive and granular soils and in any kind of rock. Methods have been developed for adequately protecting tieback tendons against corrosion and for testing every tieback to verify its long-term load-carrying capacity. However, the major problem that the industry faces today is how do we get constructable and economical tiedback walls contracted for and built with minimal claims. This paper will explore the issue of "constructability" through a look at specific problems from actual projects. From a research report from the Construction Industry Institute, Austin, Texas (1986), constructability is defined "as the optimum use of construction knowledge and experience in planning, design, procurement and field/operations to achieve overall project objectives." Maximum benefits occur when people with construction knowledge and experience become involved at the very beginning of the project." The design and installation of tiebacks has been developed primarily by specialty contractors; each contractor has evolved its own methods of performing the work, and consequently, many of the techniques are patented and proprietary. The real question is, how do we make effective use of this knowledge and experience during the design phase of the project?

Jan 1, 1991

By Michael Arnold, Bob Faulhaber, Joe Nichols

"Center Hill Dam is a critical part of the infrastructure controlling floods at the Caney Fork River and reducing flood levels at the Cumberland, lower Ohio and Mississippi Rivers. The Center Hill Dam Foundation Remediation Project was necessary to address Karst features in the foundation rocks and observed signs of distress of the dam. From 2011 to 2014 BAUER Foundation Corp. (BFC) performed deep foundation works for this project. The executed features of work include the installation of two walls. The first wall extends throughout the clay embankment into the underlying rock to provide encasement during the construction of the second wall. Its width of 7.4 feet makes it the widest diaphragm wall ever installed. The second wall is the actual seepage barrier and provides a continuous 2- feet wide wall. It extends through the first wall into the underlying rock and is up to 300 feet deep. The paper introduces the project, the requirements specified by United States Army Corps of Engineers (USACE) for encasement and barrier wall and the approaches taken by BFC. It discusses the ground conditions and describes the excavation equipment as well as the excavation methods used. A special focus is put on the steering capabilities of the hydrocutter equipment and the verticality performance.PROJECTBeginning in 2011, BFC was tasked by the USACE with the installation of a seepage barrier/cutoff wall at the Center Hill Dam Foundation Remediation project under a partially performance based specification. The remediation was necessary due to karst features in the foundation rocks and observed signs of distress, which led USACE to rate the dam with the most critical dam safety action classification (DSAC I). The executed features of work include the installation of two walls. The first wall, an encasement wall, extends vertically through the clay embankment and is embedded minimally into the underlying bedrock to provide embankment stability during the construction of the second wall, the barrier wall. The encasement wall is constructed of overlapping panels 7.4 feet (2.25 m) wide, which is the widest diaphragm wall ever installed, and up to 210 feet (64 m) deep. The second wall is the seepage barrier and provides a continuous 2 feet (0.6 m) wide wall consisting of overlapping panels. It extends through the encasement wall into the underlying bedrock and is up to 307 feet (93 m) deep. BAUER BC40 and BC50 hydrocutters mounted on MC96 and MC128 foundation cranes were used to perform the majority of the works (Figure 1). Excavations were performed under bentonite slurry (encasement wall) and water (barrier wall) and concrete was poured with the tremie method. Adding to the challenges, the project had to be executed in an environmentally sensitive area. Based on the high risk, a special focus was put on monitoring, quality control and geometric accuracy. The WallTracker information management system was used to share all relevant data between BFC and USACE (Roff et al. 2014)."

Jan 1, 2017

By B. Ramanathan

The results of a pile load test on a 1200 mm dia and 25 m long bored Cast-in-situ pile in soft rock is reported. The subsoil has a high N value of above 60 from 7 m to 21 m. The soft rock was observed below 21 m and N value exceeded 100. The theoretical calculations showed that the safe carrying capacity will be about 410 t. But the actual load test on the pile indicated that the allowable load is only about 140 t. This is attributed to the fact that the soil is cemented and loses strength due to remoulding caused by pile installation. It is concluded that great care should be exercised in determining the carrying capacity of piles in cemented soils and soft rocks and that 'N' value alone should not be used.

Jan 1, 1996

By B. B. Broms

The high transverse tensile stresses that develop in precast concrete piles during driving have been investigated experimentally from pile load tests and theoretically using the finite element method (FEM). These tensile stresses can be high enough to cause longitudinal splitting of the piles just below the pile cap. Test data and FEM indicated that the maximum transverse tensile stress will increase with increasing thickness of the cover. The maximum tensile stress can be high especially if the pile is eccentrically loaded. The results from the experimental investigation and from FEM are described in the paper as well as a simplified method based on the stress distribution in a concrete cylinder at an indirect tension test.

Jan 1, 2010

Precast prestressed concrete piles designed to be end-bearing in a sand stratum at Drax Power Station met with extremely variable resistance during driving. Some piles came to virtual refusal almost immediately on entering the sand whereas others were driven to considerable penetration with very low resistance. Redriving and load tests on piles experiencing low resistance on initial drive showed that take up in strength occurred over a relatively short period of time. Investigations involving the use of pneumatic piezometers revealed the development of significant excess pore pressures during driving. Samples from boreholes showed that piles met the least resistance when the sand had a high silt content. Comparison with the original site investigation data demonstrated the difficulties in predicting detailed pile behaviour. The varied behaviour could not be related to the original borehole logs or to SPT or static cone penetrometer results. The factors controlling pile driving behaviour were essentially geological and could only be explained with reference to local soil grading.

Jan 1, 1989

By S. K. V. Avasarala

This paper presents a case history of design, prediction, probe and production pile driving monitoring, loading tests and installation of over 3,300 prestressed concrete piles for a building complex consisting of 12, 5- and 6-story over parking buildings. The project was recently completed in three-phases over a span of 4 years. The subsoil conditions were explored by performing 25, Standard Penetration Test (SPT) borings throughout the site. Various types of driven pile foundations were considered and following an evaluation of high structural loads and site-specific constraints such as variable depth of bearing layer of Florida limestone and quality of clay and limestone layers, a prestressed concrete pile support system was selected as the most economical and effective foundation approach. The building foundations were designed for a pile capacity of 353 kN (40 tons) in compression, 45 kN (5 tons) in lateral capacity for a deflection of 0.64 cm (0.25 in.), and 133 kN (15 tons) in uplift capacity. The axial and lateral allowable pile capacity and lengths were predicted using SPT91 and LPILE computer programs, which are generally used in Florida. The validation of these capacities was derived from 144 probe piles and performance of 12 pile loading tests on selected probe piles. Prior to installation of probe or production piles, a termination criterion was established using 1-dimensional wave equation analyses in addition to the design pile embedment requirement. The predicted pile capacities compared very well with the capacities from the loading tests on probe piles. This information was effectively utilized as part of the overall quality control program to install a total of 4,186 prestressed concrete piles (including 144 probe piles) in different building areas across the project site to depths ranging from 8 to 21 m (25 to 90 ft) below existing ground elevation as part of foundation support system. This engineered, monitored, and tested foundation solution provided an effective and satisfactory basis for completion and approval of the foundation work for this 12, 5- and 6-story over parking building complex. A recent reconnaissance has indicated that all the building foundations are performing satisfactorily.

Jan 1, 1995

By Robert B. Bittner

Large diameter piles (2 to 3 m diameter, both driven and drilled) are being used more frequently by designers of bridge foundations. The use of these large piles allows the pile cap to be positioned off the bottom but usually still below water. Conventional cofferdams as shown in Figure 1 below are not suited to this type of pile cap. However, float-in cofferdams offer a viable alternative. This paper describes the float-in cofferdam system, its initial development for use on the Bath-Woolwich Bridge in Maine and its most recent application on the new Carquinez Bridge in California.

Jan 1, 2013

By Shinji Sassa, Naoki Takahashi, Eiji Kohama, Wakaki Tsuda, Hidenori Takahashi, Ikuo Towhata, Yoshiyuki Morikawa

"Abstract Deep mixing method has been employed increasingly in recent years as a countermeasure against subsoil liquefaction. Column-type solidification, however, has been thought to have little effect as a liquefaction countermeasure, because the shear deformation of unimproved soil between the columns cannot be reduced. In recent years, experimental results have been reported that imply that solidified columns can reduce the shear deformation of unimproved soil around them. A new arrangement has been proposed to mitigate lateral flow induced by liquefaction. In this study, a series of dynamic centrifuge model tests was conducted to verify the lateral flow resistance of stabilized columns. The results indicate that stabilized columns can reduce the lateral flow of liquefied ground if the column displacement and the column head rotation are restricted. This paper concludes that it is important to restrict the displacement and the rotation of the column head by surface improvement to mitigate the lateral flow of liquefied ground.INTRODUCTIONDeep mixing method has been employed increasingly in recent years as a countermeasure against subsoil liquefaction. The solidified body formed by the deep mixing method is usually block or lattice shape, composed of solidified columns that overlap each other horizontally. Lattice-type solidification has been shown to be effective as a liquefaction countermeasure despite the presence of unimproved soil inside the lattice wall, because the shear deformation of the interior soil is restrained by the wall (Suzuki et al., 1989). On the other hand, it has been thought that column-type solidification cannot reduce shear deformation of unimproved soil around columns, because the displacement of a solidified column is less restricted than that of a lattice wall. Column-type solidification has been reported to have little effect as a liquefaction countermeasure, but to be superior in terms of construction cost and applicability around existing underground structures (Koga et al., 1986). However, there are experimental results implying that solidified columns have reduced the shear deformation of unimproved soil and mitigated its liquefaction (Yasuda et al., 2003; Tanaka et al., 2003). Yamamoto et al. (2006) conducted dynamic analyses of ground improved with lattice- and column-type solidification. Their results showed that column-type solidification with an improvement ratio of more than 35% reduces excess pore water pressure generated by earthquakes. Furthermore, the new column arrangement shown in Figure 1(a) has been proposed to mitigate lateral flow induced by liquefaction. It was developed and has been verified using dynamic model testing in a 1 g field (Takahashi et al., 2010a; 2010b; 2013; Towhata et al., 2010). The stabilized columns in this configuration interrupt lateral flow in any direction, unlike those placed in square and triangular arrangements."

Jan 1, 2014

By Antal Partos

ATLAS Processing Company Shrevesport, LA initiated a major plant expansion in 1980. SITE Engineers, Inc. provided engineering consultation regarding the foundation of the vacuum unit. Four test borings were drilled and laboratory testing completed for shear strength and compressibility. Vertical drains were proposed to accelerate time rates of settlements. Steel erection was completed by May 22, 1981 with very small < 0.1 in., settlements. Hydrotesting was initiated on July 9, 1981 and completed on August 27, 1981. An average rebound of 0.3 in. was computed resulting into an average net settlement of 0.5 in. This paper describes in detail soil behavior during load testing.

Jan 1, 1992

By Peter White

A bridge reconstruction project involved driving pipe piles for the new foundations. Disturbances within soil layers at depth caused sinkholes to open up within the construction site. After a near fatal accident, the pile driving installations were suspended. The solution involved ground im­provement through cement grouting with sleeve pipes and special grout additives to minimize migration of cement grout.

Jan 1, 1997

By Patrick J. Hannigan, Geir Veslegard, Frank Rausche, Rozbeh B. Moghaddam

A common type of deep foundation used in Norway to support bridge structures is the drilled pipe piles (piles) filled with concrete reinforcement after installation. The standard installation practice is the use of down-hole hammers. Complex geology and difficult subsoil conditions in Norway causes a high variability of soil and rock layers which in turn make for differences between actual subsurface conditions and those expected from geotechnical exploratory borings. This situation is strongly noted when the foundations are not fully socketed, and the rock layer is sloped. In this particular case, special testing procedures are required to assess the drilled pile base material and evaluate the rock-socket to ensure full contact between the foundation base and the rock surface. The local standard practice to verify the latter condition, consists of coring and visually evaluating the material recovered at the bottom of the drilled pile. This paper presents a case where the coring and visual inspection were not possible and alternatively the geological material encountered at the base of the deep foundations was evaluated using force-displacement measurements. Two 1016-mm (40in) diameter open-end drilled piles identified as P02-04 and P02-05 were tested and evaluated using in-situ force-displacement data prior to filling the piles with concrete. Test results showed an average displacement of 7mm (0.28in) corresponding to 35MPa (5.1ksi) stress level for P02-04, and 7.2mm (0.28in) corresponding to a stress level of 38MPa (5.5ksi). Based on testing results, both drilled piles were within the established material assessment criterion presented by the local authorities. INTRODUCTION This paper presents a case study in Norway where the material encountered at the base of an open- end drilled pipe pile (pile) was evaluated using force-displacement data. In the deep foundation industry in Norway, it is a common practice to install piles to support transportation structures. Once the piles reach the embedment elevation, and the pile base is assessed, these are filled with concrete. In projects where sloping rock is the supporting layer, and all nominal loads are supported by the pile base resistance, assessing the material encountered at the pile base to ensure full contact with the rock becomes critical. The local practice to make this assessment consists of the use of weighted tape, coring, or inspection cameras. However, similar to any other testing and evaluation methods, these come with their own limitations. The variability associated with the use of the weighted tape, accessibility for the coring equipment to complete a coring process, or the conditions at the foundation base such as murky water or thick drilling fluids could significantly impact the photo or video quality taken at the pile base. In such conditions, it is important to consider alternate testing methods to evaluate the material at the foundation base.

Jan 1, 2018

By Scott C. Vollmer

This paper seeks to examine some of the technical factors influencing the deflection of Mechanically Stabilized Earth (MSE) retaining walls based on the authors&apos; field observation of numerous structures. Excessive deflections can be unsightly and can be perceived as wall failure. Deflections can cause cracking or gapping of the facing units and general misalignment. Deflection of the reinforced backfill zone behind the wall face can result in settlement of the backfill zone and adjacent pavement cracking. Deflections can be the result of excessive movement external or internal to the reinforced soil structure. This paper only examines internal factors affecting wall deflections. External factors such as foundation settlement are not discussed.

Jan 1, 2003

By Feng Yongxuan

Anchored sheep pile is normally used in deep excavations, many of which only require stability in accordance with Terzaghi theory. In this paper, based on the experience, new lateral earth pressure method is adopted taking account into interaction among soil, anchors and sheet piles so that a group for the project under very difficult conditions and very severe requirments, especially, for the displacements are determined according to that mentioned above. During and after construction, displacements monitoring were carried out for about four months, which was proved that there was a little difference between calculation and practice.

Jan 1, 1991

By Per Eriksson

For light buildings on clay, foundations on L/C-columns is in many cases a competitive alternative to piles when the thickness of the clay is moderate (<20 m). The method is applicable for the above mentioned depth when the clay is normally consolidated, and for thicker deposits when the clay is overconsolidated at depth. This case study concerns a shopping mall in Nordby, Sweden, founded on L/C-columns (5-15 m in length) and generally spaced 1.45-2.0 m (spacing 0.7 m was used below pillars). The base slab was built as a raft foundation, using fibre reinforced concrete.

Jan 1, 2000

By Paul J. Axtell

The results of in-situ geophysical cross-hole tests on improved soil by soil mixing (SM) and jet grouting (JG) are described. This testing was conducted on soil improved by SM and JG columns constructed in the downstream free-field of Tuttle Creek Dam near Manhattan, Kansas as part of the seismic retrofit. Results of similar geophysical testing performed on untreated soil in the vicinity of the Downstream Test Program (DTP) area, as well as beneath the embankment at several locations, are also described and used for comparison purposes. In-situ shear moduli are also compared with those determined in laboratory resonant column tests. The increase in stress wave velocities and associated shear moduli by SM and JG treatment are presented for use in liquefaction potential and seismic deformation analyses of SM or JG treated soil. This data is required to determine the decrease in liquefaction potential and earthquake-induced permanent deformations due to SM or JG with respect to that of untreated soil.

Jan 1, 2008

By Brian R. Zuckerman

The Capitol Area East End Complex is currently being constructed under contract with the State of California Department of General Services on two sites adjacent to the grounds of the California State Capitol Building in downtown Sacramento. The complex will consolidate the headquarters of the Departments of Health Services and Education, which currently occupy several facilities located throughout Sacramento. When completed in 2003, the complex will be the largest civic office project in California history, with approximately 1.5 million square feet of office space and housing nearly 6,300 state workers. The total project is being constructed on five separate blocks in downtown Sacramento, Blocks 171 through 174 and 225. Separate design/build contracts were executed for the construction on Blocks 171 through 174 and the construction on Block 225. The scope of this paper is limited to construction on Blocks 171 through 174, which comprise a square, two blocks on a side, bounded by 15th, 17th, L, and N streets, located immediately to the east of Capitol Park and the State Capitol Building, as pictured in the image shown below.

Jan 1, 2002

By N. C. Matheson

The West&apos;s Shell Pile has been used on sites with very soft ground conditions for over 60 years. Fibre reinforced precast concrete shells 900mm long are threadled onto an internal mandrel which can be extended according to the depth driven to attain the load bearing resistance. On completion of driving the mandrel is removed leaving the precast shells to form a permanent lining to the cast insitu concrete core. To give resistance to high contamination, a tar based epoxy coat is sprayed on the outside of the shells or a flexible PVC liner is installed inside the shells to protect the core. Fundamental to the resistance to contamination is the quality of the precast fibre reinforced concrete shell, the mix design and method of manufacture. A series of detailed laboratory experiments were carried out using samples immersed in concentrated acid and sulphate solution. The long term effects of exposure to contamination is recorded in the case studies of existing piles at two gasworks sites.

Jan 1, 1989

By Stan Merjan

Composite piles with precast concrete tapered pile tips (TPT Composite Piles - U.S. and foreign patents) are a new and important addition to the piling types available to the construction industry. TPT Piles were invented by Stanley Merjan, Vice President of Underpinning & Foundation Constructors, Inc.. U. F. C. installs these piles in the Northeast United States and licenses piling contractors in other parts of the country. TPT Piles have been developed for use in sandy subsoils at depths to 70 feet or greater. The TPT system (see Figure 1) is simple. A pile stem of conventional material (shell, pipe, steel, wood, precast concrete) is connected to a socket formed in a precast concrete tapered pile tip (TPT). This composite assembly is then driven as a unit by ordinary pile driving methods until adequate driving resistance (established by formula or load tests) is met in a suitable soil strata. This driving resistance develops from the displacement and densification produced by the TPT. Many combinations of tip shapes and stems are available to suit particular job requirements with respect to subsoil conditions and pile capacities. TPT Piles should be considered for use on a wide variety of jobs. The advantages offered by a TPT installation include: ? High capacity piles in marginal soils ? Minimal lengths required to produce these capacities ? The use of conventional pile driving equipment and procedures ? Pile inspection techniques that are the same as for ordinary pile driving Furthermore, TPT piles are economical due to a combination of a low cost per ton of pile capacity and high productivity, both of which lead to significant savings in foundation costs and time required to complete foundation work.

Jan 1, 1987