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By Frank Haehnig, Kurt Kogler

"With a height of 200 m, a crown width of 626 m and a concrete volume of 1.6 million m³, the Kölnbrein Dam in the upper Malta valley in Carinthia / Austria is the largest concrete dam in Austria. Boasting a storage capacity of 200 million m³ with a received water load of 54 MN, this is one of the strongest arch dams in the world.During its construction from 1974 to 1977, the dam was equipped with a comprehensive monitoring system capable of comparing developing deformations and stresses with the design values.With a planned reservoir level of 1,900 m a.s.l. the dam saw the reservoir level of 1,860 m a.s.l. breached in the year 1978. This led to extremely high seepage losses of up to 200 ltr/sec and a rise in the foundation water pressure up to 100% of the dam’s height. These observations were caused by the development of horizontal cracks in the area of the middle dam blocks, between the lowest inspection walkway and the waterside.As a consequence, power plant operations had to significantly be reduced and a number of additional measures were carried out – though these did not lead to the desired sealings.The developer subsequently decided that the dam should undergo a general rehabilitation from 1998 to 1994 in accordance with a concept developed by Professor Lombardi. This concept involved erecting a 50 m high support structure with a concrete volume of 500,000 m³ on the airside of the dam, along with the addition of neoprene bearings to transfer 1.2 million tons of the horizontal load. These measures were able to reduce the deformations in the dam enough so that mostly load-bearing injections into the cracks in the dam’s concrete could successfully be carried out by way of targeted grouting measures using injection resin (RODUR) specifically developed for this purpose.In the years 1998 - 1994, a total of 130,000 m of grouting, monitoring and control drillings were executed, and around 200,000 kg of synthetic resin was injected into the cracks in the dam’s concrete.These measures have ensured the dam‘s uninterrupted operation since 1994. A number of small re- injections were again carried out on the contact surface in the years 2011 and 2012."

Jan 1, 2016

By Jom Gentry

Acrylamide chemical grout (C3H2NO) has been successfully used for over 50 years to control groundwater and stop infiltration. This paper will address three unique projects involving the control of groundwater with each study providing special circumstances and geological conditions: encapsulation of radioactive hazardous waste in the United States, a tailings dam for a large copper/gold mine in Argentina and 27 miles of leaking subway in Canada. The primary reasons for selecting acrylamide grout were based on the following characteristics: thinnest chemical grout on the market, a true solution grout which contains no suspended solids in the blended product, flexible gel set times, and a 362 year half-life in soil as determined by the U.S. Department of Energy.

By Masanoub R. Fujioka

A brief discussion of the methodologies involved in dewatering practices, particularly as used in Hawaii in coralline formations. A description of early dewatering practices includes a number of case histories; later dewatering practices also are detailed with case histories. There were disasters and some successes. Grouting generally was not successful. Deep wells are technically feasible and generally the economical solution to deep basement construction.

Jan 1, 1986

By Michael Perlow Jr

A modification of the original Davisson Offset Limit (DOL) is presented for drilled foundations using soil quake (QDOL) factors ranging from 2 to 6. A further modification of the Davisson Offset Limit has also been developed using helical pile soil quake values (HDOL) based upon helix diameter. In addition, the initial tangent slope (IS) of the pile load test displacement curve is used in lieu of the calculated elastic slope (ES) to eliminate many of the uncertainties associated with determining the drilled foundation pile elastic modulus. The QDOL and HDOL load test methods do not require any graphical interpolation and provide easy simple ultimate pile capacity interpretation methods where drilled foundation pile load tests are not carried to plunging failure. Drilled foundation and helical pile load test case studies are presented to demonstrate the use of the modified soil quake QDOL and HDOL Methods.

By Miklós Kovács

A new type of the cast in situ piles is introduced. The installation of the new pile is based on a pushing in/gaining back procedure. A temporarily closed tip element with square shaped cross-section being attached to an upper circular shaft tube is vibrated into the soil. The steel armature is embedded. Concrete is poured into the tube and, the whole structure is gained back while the tip is in opened position. The width of the tip is less than or equal to 40 cm. The maximum length of the pile is about of 14 m. Great bearing capacity is resulted from the double soil compaction effect. No spoil is generated and, the pile construction can be controlled. The paper presents the results of four loading test at three sites with some soil data.

Jan 1, 2002

By Xiaocen Lu, Guowei Li, Jiantao Wu, Thang N. Nguyen, Andrew C. Amenuvor

"This paper investigates the effect of driving a group of 52 open-ended Prestressed High Strength Concrete (PHC) piles on an existing highway embankment based on field measurements of excess pore pressure and lateral soil displacement. Excess pore pressure due to pile driving increased with depth and decreased with increasing distance from the pile, influencing a distance of 43 pile diameters. For pile groups, the rate of dissipation of excess pore pressure decreased with increasing depth and averaged 79% in 20 days, during which maximum ultimate bearing capacity was not yet attained. Lateral soil displacement continued to increase for a period of time after the end of pile driving and this could have resulted in significant inclination of piles if pile installation was too quick and pile spacing was too small. Lateral soil displacement due to pile group decreased with decreasing distance to the existing embankment as a result of high soil density produced by the embankment loading. The results also indicate that the effect of pile group installation on the existing embankment is negligible.INTRODUCTIONPile driving can cause excessive lateral displacement of soil and heaving of the ground surface, which may adversely affect nearby structures. In addition, lateral deformation and excess pore water pressure resulting from pile driving can exert lateral pressures and vertical forces on the piles, and impact negatively on the project and its surroundings. Therefore, it is important to evaluate the influence of pile driving on the nearby structures as well as the project itself when expansion works are carried out.Recent years have seen some development in the application of field tests for studying soil disturbance due to piles, and these tests usually involves pore water pressure and lateral soil displacement monitoring during pile driving. Results of field experiments performed by Reese and Seed (1957) in San Francisco Bay Mud with instrumented piles showed that pile installation generated large pore water pressures at the pile surface, with only slight increase at a distance of 15 pile diameters away. The measurements indicated that the increase in pore water pressures can exceed the initial total overburden pressure. Holtz and Lowitz (1965) reported a decrease in undrained shear strength immediately after pile installation, which was largely recovered after full pore pressure dissipation for field measurements within 1.5–2 pile diameters from the pile surface. Hwang et al. (2001) presented results of large scale pile driving tests where maximum excess pore water pressure generated decreased rapidly with increasing distance from pile. The excess pore water pressure became negligible at 15 pile diameters from the pile. Their results also showed that lateral displacement of the ground decreased with increasing distance from the pile. Pestana et al. (2002) carried out full-scale closed ended pile tests in the Young Bay Mud deposit. Higher excess pore pressures were observed for points closer to the pile, which decreased with increasing distance from the pile wall. Exponential decay of excess pore pressure with time was also noted. An 80% dissipation of excess pore pressure was achieved for soils more than one pile diameter away from the pile wall between 50 to 80 days. Lateral deformation generally decreased with increasing distance from pile wall, whilst varying erratically with depth. Bozozuk et al. (1978) reported on soil disturbance due to driving of 116 concrete piles in sensitive marine clays in a construction project. Maximum pore water pressures after pile driving within the group, and 6m (20 pile diameters) from the group were over 35-40% of the total overburden pressures, and the influence of pile driving on pore water pressure at 20m away from the group was very small. Cooke and Price (1973) studied a 168-mm-diameter instrumented pile jacked into over consolidated London clay. Outward lateral displacements ranging"

Jan 1, 2016

By Suzanne R. Hess-Brittelle, Sharon L. Schulz, Tyler J. Quick, Amy F. Ebnet

"Abiquiu Dam is a rolled earth fill dam with impermeable core located on the Rio Chama in New Mexico. Abiquiu has had a history of excessive seepage through the fractured sandstone abutments since water was first impounded in 1963. The foundation was treated with a single row grout curtain in the cutoff trench prior to placement of the embankment. During the 1960’s and 1970’s, the grout curtain was extended 1,000 ft. into both abutments and sections of the foundation beneath the embankment were regrouted. Grouting of the foundation beneath the embankment required drilling through the embankment. Drilling fluid loss or loss of circulation within the impervious core was observed during multiple phases of supplementary grouting and during verification drilling following the 1970’s grouting program. It is likely that the drilling methods employed for these grouting and drilling programs caused hydraulic fracturing of the impervious core. The fluid losses in the embankment may be related to seasonal shutdown layers in the embankment or benches in the abutment foundations. In addition, it is likely that the impervious core was fractured from grout pressures during installation of grout pipe through the embankment.INTRODUCTIONAbiquiu Dam is located on the Rio Chama in New Mexico and consists of a rolled earth fill dam with impermeable core, controlled outlet works, and an uncontrolled rock-cut spillway. The dam was authorized for flood control and sediment retention and was designed as a dry dam, holding flood pools for relatively short durations. The foundation is comprised of Permian and Triassic age, interbedded mudstones and sandstones that were deposited in an active braided stream system. Sandstones are moderately fractured and have variable aperture and infilling. Generally speaking, joints are near vertical. Abiquiu has had a history of excessive seepage through the fractured sandstone abutments since water was first impounded in 1963. The foundation was treated with a single row grout curtain in the cutoff trench prior to placement of the embankment. In 1966-1968, the grout curtain was extended 500-ft into the left abutment and the foundation beneath a 560 ft. section of the embankment was re-grouted. In 1978-1980, the grout curtain was extended 1,000 ft. into the right abutment, an additional 500 ft into the left abutment and the foundation beneath the right 520-ft section of the embankment was re-grouted. The alignments of these grout programs are shown in Figure 1. Grouting of the foundation beneath the embankment required drilling through the embankment. Drilling fluid loss or loss of circulation within the impervious core was observed during both phases of supplementary grouting and during verification drilling following the 1978-80 grouting program. It is likely that the drilling methods employed for these grouting and drilling programs caused hydraulic fracturing of the impervious core. In addition, it is likely that the impervious core was fractured from grout pressures during installation of grout pipe through the embankment. This paper provides a summary of the drilling and grouting methods used during these programs and the potential for damage to the embankment."

Jan 1, 2016

By Cheng Lin

The Group Equivalent Pile (GEP) approach was proposed by researchers to analyze a laterally loaded pile group. This approach enables engineers to evaluate the behavior of a pile group in single pile analysis software, such as LPILE. A previous study showed that the calculated results using the GEP approach for piles agreed well with field test data. To evaluate the accuracy of the GEP method for analyzing laterally loaded shafts, two case studies with different shaft diameters were performed in this study. The comparisons showed that the calculated results using the GEP method and considering the contribution of the shaft cap if embedded generally agreed with the measured from the full-scale tests.

Jan 1, 2009

By Gilbert Chuah, Peter Middendorp, Joost Bakker, Soon-Hoe Chew

"The Rapid Load Testing (RLT) of foundation piles has been applied worldwide since 1984. Several International and national codes are available, such as the Japanese Code of Practice (2002), ASTM D7383-2010, German recommendation on Piling (2012) and Eurocode (2015). RLT methods like Statnamic and StatRapid are gaining popularity in Asia, Europe and North America. For checking the performance of piles, they are more economical, faster and environmentally friendly than Static Load Testing (SLT), while yielding good correlations with SLT results through an objective analysis method. To date (October 2016) hundreds of piles have been successfully tested by RLT method in Singapore. A number of these RLT tests were coupled with static load testing correlation tests, some of them with instrumentation for shaft load transferred. Examples of some correlation results for foundations installed in various geological formations in Singapore are presented in the paper. The findings from these results indicate that loading rate effects are negligible for Rapid Load Test results when foundations are socketed in competent non-cohesive soil layers and derive most of their capacity from these soil layers.INTRODUCTIONRapid Load Testing (RLT), by which a quasi-static load is applied to a foundation pile, is used increasingly as an alternative to Static Load Testing (SLT) for cast in-situ piles, such as drilled shafts or bored piles. It is recognized nowadays that the determination of the pile capacity with Dynamic Load Testing (DLT) through signal matching techniques such as CAPWAP, TNOWAVE and AllWave-DLT, yield a wide spread of results for cast in-situ piles (Stahlmann et. al, 2012), making it practically very difficult, if not impossible to calibrate the DLT results with SLT results. This spread is due to the empirical and subjective assumptions that are used to interpret the test data, especially for cast insitu piles (Holeyman et al. 2001, Viana da Fonseca in 2008, Herten et al, 2013). This is further complicated by the inhomogeneity of the concrete and variable cross-sections over the pile length for the cast in-situ piles."

Jan 1, 1900

By Brian Wilson, Franz-Werner Gerressen

"Cutter Soil Mixing, also known as CSM, was developed in Europe as an alternate method of Deep Mixing to the more traditional single and multiple auger techniques, and brought to market by Bauer Maschinen GmbH (Bauer), towards the end of 2003. Initial development of the technique had been completed in a joint venture between Bauer and Bachy Soletanche. In 2004 the concept was introduced to the North American market. Continued development of the method and demonstration of its versatility, both in terms of applications and applicable soil types has seen a steady growth in the number of designs incorporating the approach, and contractors offering the technique. This paper provides a brief overview of the variety and size of projects and applications where the method has been adopted, discusses some lessons learned with respect to equipment operation as well as the improvements that have been introduced to the equipment, and briefly reviews the current state of practice, as well as some of the associated on-going research and development.BACKGROUNDCutter Soil Mixing (CSM) is a technique for deep soil mixing that was initially developed as a collaborative effort between Bauer Maschinen (Bauer) and Bachy Soletanche, but which ultimately resulted in the separate development of two somewhat different brands of CSM tool. The Bauer brand of CSM entered the European market in 2004, and was first promoted in the North American market in late 2004, with the first project starting in 2005. The Bachy Soletanche brand, sometimes referred to as “Geomix” was first marketed in Europe in 2005 and the first model introduced in North America in 2007.The development of the Cutter Soil Mixing technique utilized the experiences gained from Trench Cutter/Hydrofraise equipment, developing a technique that incorporates two cutting wheels rotating about a horizontal axis as opposed to the more conventional deep soil mixing approach which utilizes augers and mixing paddles rotating about vertical axes. Whereas the Trench Cutter/Hydrofraise technique excavates the soil from within a panel, and supports the open hole using a bentonite slurry, the CSM technique cuts and displaces the soil whilst pumping a slurry/grout directly into the soil through a port located between the wheels. The combination of cutting the soil while introducing an appropriate volume of slurry effectively fluidizes the column of soil around and above the cutter head. While this process achieves a high degree of mixing, even on the downward cutting stroke, thorough in-situ mixing typically occurs on the withdrawal stroke, when most of the slurry is added."

Jan 1, 2015

By Chris Sammon

The Block 75 portion of the City Creek redevelopment project in Salt Lake City required multiple shoring walls surrounding the 6 acre site constructed to depths ranging from sixty-five to ninety feet below original street grade. Shoring for the project was challenging due to site soils consisting of cobbles, sands and gravels, interlayered lakebed silty clay and fine sandy silt with incised stream deposits of silty/clayey sand and gravels combined with a high groundwater table. Moreover, several abutting structures each with a unique foundation system would be directly or indirectly supported by the shoring system. Three sections of interest are the shoring walls constructed at Main Street, Deseret Trust Building and Eagle Gate Tower. Main Street shoring extended to as much as sixty-five feet below street grade and utilized existing basement walls anchored in place in the upper zones with soil nail walls with pre-installed vertical elements for face stabilization below. Data are presented which illustrates the effect dewatering had on the settlement of the Main Street Shoring. The Deseret Trust Tower shoring supported a 12 story, historical masonry building. Site conditions dictated a separate design for the east side and the north side of the building allowing comparison of relative performance between these walls. Settlements of this structure were controlled by installing micropiles through the 90 year old structures spread footings. Shoring for the Eagle Gate Tower was to be constructed immediately adjacent to a mat supported 22 story high rise structure. This shoring system combined secant piles, ground anchors and incorporated existing abandoned-in-place pipe piles with infilling high pressure jet grouting to create a cutoff wall and eliminate the adverse impacts of dewatering below this sensitive foundation.

Jan 1, 2010

By Kenneth A. Pidgeon

This paper presents a case history on mitigating vibration problems associated with the installation of steel sheetpiles. The project in-cludes installation of steel sheetpiles for a utility trench within 40 feet (12.2 meters) of a very sensitive manufacturing facility. Numerous production line quality control instruments and manufacturing processes within the manufacturing facility are extremely sensitive to vibrations. To minimize the impact to the owner, we specified that the contractor perform a vibration study using different types of pile hammers. The results and conclusions of the vibration study are presented in this paper.

Jan 1, 1995

By Z. G. Lin

In Xian, China, compaction by means of soil (or lime-soil) piles is one of the effective methods widely used for densifying loess and eliminating its collapsibility. However, as a result of groundwater table rising, it is no longer applicable in many areas. This paper is the summary of the first-time use in Xian of sand-gravel compaction piles aimed at densifying the miscellaneous fill (already partially under water) and saturated loess at a certain project site. In-situ tests, conducted before and after the treatment and including several kinds of penetration tests backed up and confirmed by a set of plate loading tests, yielded very satisfactory results, strongly testifying to the viability of the method.

Jan 1, 2010

By Mu Chen, Ye-Shuang Xu, Dong-Wei Hou, Shui-Long Shen, Huai-Na Wu

"This paper presents a laboratory investigation on the mechanical behaviors of the cement-clay admixture improved by polypropylene fiber. Cement can significantly improve the clay admixture. The fiber additive also improves the strength and ductility of the improved clay. The Unconfined Compression Strength (UCS) of the polypropylene fiber-reinforced cement-clay presents an overall trend to grow with the increase of fiber length. The improved clay reached its peak strength at the fiber content of 0.5%. Then the UCS of the improved clay will slowly reverse if the fiber content continues to rise. For study of curing time, improved clay behaves better in its early strength, but an inhibition will be brought about if fibers are excessive.INTRODUCTIONGround improvement technology is essential for construction of structures in soft ground. Some traditional techniques often cost much but result in little. For instance, along the coastal region of China, soft ground is often improved by backfill with high quality sandy soil transported far away, leading to high additional haulage costs and long construction period. Reutilizing the excavated soil as backfill or subgrade after treatment, by contrast, will be more economical and effective (Hufenus et al., 2006). Many researches have been conducted to improve the compression strength of soft soil, among which, the method of mixing the soft soil with cement and fly ash is one of the most common ways (Kolias et al., 2005; Horpibulsuk et al., 2009; Porcino et al., 2012). It is known that soil resists well against compression and shear force but behaves poorly in resistance to tension. Therefore, utilizing tensile elements such as fibers and strips to improve the tensile strength will be effective because of its strength isotropy, better durability and cost effective (Haeri et al., 2000; Kaniraj and Havanagi, 2001; Consoli et al., 2010)."

Jan 1, 2015

By D. M. Holloway

As a part of the 1-15 Reconstruction Project, static and dynamic (high-strain) testing methods formed the basis to estimate long-term axial capacities, and to assess the magnitudes of bearing capacity gains (setup) from the end of installation to the time of static/dynamic tests weeks later. This paper summarizes the results of nine full scale pile load tests to failure in compression, and how the designers used these data to finalize pile selection and penetration criteria bridge-by-bridge in the final design stages. Soil conditions along the project alignment ranged from deep, lightly over-consolidated Lake Bonneville clays interbedded with granular strata of varying consistency, to sites dominated by dense alluvial deposits of cohesionless soils well above the water table. The test sites were selected to bracket the conditions that are expected. Twelve-, 16-, and 24-inch-OD pipe piles are to be used to support the new bridges. The team plans to impact-drive all piles closed-end to final penetrations. The test piles varied from 35-ft-long pipes driven to refusal in the shallow dense sands at some sites, to 115-ft-long pipes stopping at 3 blows per foot in predominantly cohesive deposits. The capacities gained with time proved to be reasonably predictable, and significant setup was noted both in the cohesive and cohesionless strata. The test program objectives included providing the means to estimate long-term capacities from short-term (24- to 48-hour) restrikes following installation of foundation piles during production driving operations.

Jan 1, 1998

By Kevin P. Gleckler, Steven C. Highfill

"Escalators to access platforms for the Second Avenue Subway Station at 72nd Street in Manhattan are to be installed in the basement of an existing 19-Story residential building. The escalators, which extend below the existing building foundations, require excavation of an inclined rock cavern up to 80-feet deep. Underpinning of columns within the 19-story building as well as a stone masonry party wall and columns for an adjacent 5-story building was completed prior to excavation of the rock cavern to ensure structural stability.This paper will discuss the analysis and design of the underpinning system, the installation and load transfer procedures and the cavern excavation immediately below. The underpinning system was subject to very strict deformation limits and to electronic monitoring prior to and throughout the load transfer and construction process. Key details such as the load transfer mechanism between the reinforced concrete column and the temporary structural steel underpinning frame will be discussed. The challenging rock excavation process will be described which utilized conventional equipment and pattern drilling with Damite rock splitting mortar.INTRODUCTIONPhase 1 of the Second Avenue Subway is being built by MTA Capital Construction (MTACC) to improve subway service on the east side of Manhattan. Entrance 1 for the 72nd Street Station of the Second Avenue Subway is located on the east side of 2nd Avenue at the corner of E 69th Street in New York City. Access to the station mezzanine, approximately 80-feet below grade, is designed to be routed through the basement of an existing 19-story residential building. From the sidewalk, stairs and escalators within the width of sidewalk connect the riding public to a basement level mezzanine, which turns into the building at roughly 16 feet below grade (Fig. 1). Riders then connect to three long escalators to arrive at the station mezzanine. The escalators are to be installed within an inclined and arched cast-in-place (CIP) concrete lined rock cavern (Fig. 2). Construction of both the entrance into the basement and the escalator cavern require the transfer of columns within the 19-story building. Excavation of the escalator cavern also impacts the foundation support for columns and a load bearing party wall for the 5-story residential building immediately to the north. Two stages of load transfer were used at each location. The Stage 1 transfer used a temporary underpinning system to unload the current structure which allowed for construction of the permanent transfer girders. Stage 2 transferred the load from the temporary system to the permanent transfer girders."

Jan 1, 2016

By Edward L. Hajduk

During sonic logging quality control testing of the drilled shaft foundations for the replacement bridges crossing the Broad and Chechessee Rivers for SC 170 in Beaufort County, South Carolina, irregular signals were observed on a consistent basis near the shaft top elevations. These irregular sonic signals were attributed to access tube ?debonding?, which is the separation of the access tubing from the surrounding concrete. A total of 160 drilled shafts were installed for this project, of which 41 were evaluated using sonic logging testing. Both PVC and steel access tubes were used during the project to allow for sonic logging testing. This paper details the investigation of access tube debonding with time, discusses the solutions used to minimize access tube ?debonding?, and presents the results of the sonic logging testing for the entire project. The solution selected, installation of PVC along the pile length and steel access tubing within 40 feet from the top of shaft, allowed for reliable sonic logging to effectively evaluate the upper portions of the drilled shafts.

Jan 1, 2004

By Caciola Jr. Joseph J., Nidal M. AbiSaab

"Thanks in great part to the geology of the New York City Metropolitan area, mini-caissons are a popular choice for deep foundations. These drilled elements are readily available, easy to install with minimal impact on adjacent structures, and can be designed with large compressive and tensile capacities. Despite the frequency with which they are employed, the engineering design community is divided over several of the underlying principles governing the design of mini-caissons. This paper seeks to draw attention to several of these issues in an effort to encourage further research and discussion, namely: (1) how the allowable stresses have changed for the NYC Building Code over time, (2) the inconsistent load transfer mechanisms considered for geotechnical capacity, and (3) the role of the permanent steel casing towards structural capacities of mini-caissons.INTRODUCTIONIn the local construction nomenclature, mini-caissons are drilled deep foundation elements which derive their capacity from a socket in rock. A permanent steel casing (commonly between 7- and 24-inches in diameter) aides the drilling through overburden soils to the top of bedrock. Afterwards, an uncased rock socket is drilled into the bedrock and the inside of the casing and rock socket is inspected by means of portable video equipment. After inspection, the interior of the socket and casing is filled with steel reinforcement and concrete or grout. The casing-soil interface is generally ignored for axial design purposes and the full geotechnical compressive or tensile capacity is assumed to be generated in the rock socket. Figure 1 shows a typical mini-caisson cross section.Mini-caissons have been used for decades in the New York City area for a number of reasons. They have historically been proven to develop high axial capacities in the city’s metamorphic rock (Tamaro et. al. 2000), often exceeding 300- to 500-tons. Additionally, their method of installation (drilling) is generally able to bypass layers of dense Glacial Till, boulders, and manmade fill which would interfere with the installation of other pile types (e.g. driven piles, auger cast piles). Further they are able to extend to depths exceeding 50-ft to reach bedrock underlying a site, making them a useful tool in areas where rock is relatively deep or varied in elevation. Drilled casing installation also results in fewer vibrations and disturbances to adjacent structures and can occur in areas of restricted access (a constant concern for any project in a dense urban environment such as NYC)."

Jan 1, 2016

By Zhang Yaonian

This paper describes full-scale tests on ten large bored piles with grouted end conducted for three projects in the urban area of Fuzhou city. Test program included site investigation, pile installation and end grouting. The piles were instrumented with strain gages and load cells to determine load distribution in the piles. Test results showed that end grouting improves load-settlement performance of bored pile. End grouting significantly increases the shaft resistance near the pile end. The better the end condition, the greater the shaft resistance. The average shaft resistance of the bored piles with grouted end is much higher than that of piles without grouting.

Jan 1, 2004

By Ping Yang, Tian-bin Li, Min-hui Wu

"The process of filtrate loss of low solid-phase drilling fluid at different content of polyanionic cellulose is investigated by the standard filtration test. The test results showed that when time of filtration is same, the filtrate volume decreases linearly with the increase of content of polyanionic cellulose. When content of polyanionic cellulose is same, the velocity of filter loss decreases nonlinearly with the increase of time and the velocity of filter loss will reach a stable value. The filtrate volume in 7 to 8 minutes can reach half of the total filtrate volume. At the same time, the velocity of filter loss of drilling fluid decreases nonlinearly with the increase of viscosity. When apparent viscosity is between 3.5~4.15 mPa.s, decrease speed of velocity of filter loss is quick. The results are helpful for characteristics evaluation of filtrate loss of drilling fluid and control of filtrate loss.IntroductionDuring the process of drilling, water of drilling fluid can leakage into stratum, the water can result in instability and collapse of borehole wall. At the same time, the original ratio of drilling fluid will change. The density of drilling fluid will increase, the performance of the drilling fluid will change. Controlling amount of filtration is important to drill successfully. The additives of controlling filtrate loss are mainly two types, particle materials and polymer materials. High-molecular polymer is a kind of high-molecular material, has the adsorption effect, high polymer protection, can improve the advantages of slurry viscosity (Xu,2004 and Dehghanpour,2001). Some scholars carried out some study on the polymer material fluid loss agent in recent years, these study mainly focused on CMC, HEC, MHEC, CMHEC, starch and its derivatives(Zhang,2005 and Chevron,2009).About PAC (polyanionic cellulose) as drilling mud additives, a few of scholars carried out some relevant work. Plank (1992) applied PAC into ordinary freshwater drilling fluid and analyzed temperature stability of freshwater drilling fluid. Bennion (2000) applied PAC into drilling fluid and analyzed effect of polyanionic cellulose on strata inhibitory. Huang (2011) analyzed effect of PAC on properties of the high-density water-based drilling fluid. Mahto (2004) applied PAC into fresh water and salt-water drilling fluid and analyzed effect of PAC on rheological properties of the drilling fluid. Wang (2008) applied PAC into alkaline drilling fluid to study various performance of drilling fluid. PAC is a renewable resource and has good application prospect (Ankara, 2005). So it is very important to understand the effect of PAC on filtration process of drilling fluid.The test was conducted by changing the content of the PAC in drilling fluid. The object of this paper is to understand effect of polyanionic cellulose on filtration process of the low solid-phase drilling fluid."

Jan 1, 2017