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By Massimo Poggio, Gabriele Balconi, Andrea M. R. Pettinaroli, Mario Ruggiero, Riccardo Castellanza

Grouting technologies are ground treatment techniques used for modifying the behaviour of a mass of soil or rock by injecting a mixture. The sleeved port pipes (also called Tube A Manchette) are highly diffused for grouting treatment of coarse soils and fissured rocks. This paper describes a combination of jet grouting and rock grouting with MPSP (multiple packer sleeve pipe) technique that has been used to realize waterproof curtains under fluvial structures for a cascade hydro-power plant. This is composed by five mini hydro-power plants, placed along the Iskar River, in Bulgaria, and composed by a penstock followed by the power house, a spillway, and an earth dam containing the reservoir. The geology of the site is characterized by an upper alluvial deposit lying over the bedrock. In each site, similar treatments were carried out: an impervious curtain along the plant section, obtained by executing jet-grouting columns in the surficial alluvial layers and grouting the underlying fractured rock by means of port pipes. The temporary embankment, built during the works for protecting each site from the possible river floods, has been waterproofed and stabilized by reinforced jet-grouting columns. The grouting processes have been controlled and monitored by a computerized system. INTRODUCTION The Iskar river cascade hydropower plant is situated northern of Sofia, Bulgaria, and it is composed by nine plants. Actually five of them have been built and produce energy. Each plant is composed by a penstock followed by the turbine building, a spillway, and an earth dam that contains the reservoir. The Iskar rivers runs in a narrow valley characterized by diorite or diabase rocks, with an upper deposit of alluvial soil, composed mainly by gravel and sand. Each plant requires an impervious curtain under the structures and in correspondence of the earth dam: this has been obtained by means of a jet grouting treatment of the alluvial coarse soil, and a grouting treatment with cement mixtures of the underlying rock using the MPSP technology. During the construction of the structures, the site has been shielded from the river water by a temporary earth embankment that has been statically improved and waterproofed by jet grouting columns reinforced with steel tubes; this allowed to work without interruption even in case of flood of the Iskar river.

Jan 1, 2019

By Almer E. C. van der Stoel

"Abstract This paper deals with assessing the bearing capacity of existing wood pile foundations. With a wide range of restoration projects being performed in the Netherlands, on many locations deep excavations need to be constructed next to existing, many times listed buildings. The building are founded on piles that are often centuries old, so a close evaluation of the remaining bearing capacity, combined with and assessment of the influence of the excavation is in place.After giving an introduction on Dutch pile foundations, a methodology is described to assess the bearing capacity. Aspects as physical foundation investigation, determination of the current bearing capacity and a calculation of the bearing capacity in the new situation are discussed. The results of both analytical and Plaxis calculations are outlined, focussing on how to practically use this approach in renovation projects. Finally, cases studies of the successful application of this approach in major renovation projects in Amsterdam, such as the Conservatorium Hotel and the New Rijksmuseum are used to illustrate the successful application of this approach.A Short Dutch Pile Foundation History (based on Van der Stoel, 2001)The first houses built in Amsterdam, in the 12th century, were very light constructions of timber without foundations. Because of the soft peat layers found in Amsterdam, the houses there suffered from damage due to settlement. In the 13th century, castles and churches were increasingly built of bricks, which made it necessary to provide support for bigger loads. Under the wall of the construction a trench was dug, and this was filled on either side by alder fascines. Between the fascines small wood piles were driven (by hand) on which another series of fascines was put. On top of this construction, were placed oak slabs on which the bricks were then laid. From that moment on, a problem was caused by the decay of wood foundation elements in the humid soil. In 1503 a law was introduced forbidding building foundations on public streets without permission of the Building Inspection (to keep the fronts of the buildings in a straight line). In 1528 a law requiring permission from the local authorities for all building activities replaced this law. In this period developments started which led to the use of the type of foundation that can be considered the mother of the current “typical” Dutch pile foundation. The piles used in this period were shaft- bearing piles about 5 to 7 meters long. The mostly pine piles were driven between oak beams, which were placed on either sides of a trench, after which other oak beams were laid across at regular spaces: the so called “pile bent” pile foundation (Figure 1)."

Jan 1, 2014

By Abid Adekunte

"Engineers and developers have witnessed the growing popularity of deep basement structures as components of urban commercial and residential developments. This is often attributed to inadequate surface parking facilities in urban centres and a somewhat popular belief that underground parking facilities improve both commercial and aesthetic values of urban structures. For many years, diaphragm walls and sheet pile walls have been widely accepted as effective deep excavation support systems for basement construction in urbanised zones. However, these are now being replaced by bored pile retaining walls as preferred earth retention systems of choice on many projects for several reasons, which may include economy, faster installation process, reduced space requirement for machinery and ancillary equipment, flexural rigidity and axial capacities.However, there are complexities associated with the use of bored pile retaining walls on urban developments. These include; limitations due to vertical and horizontal installation tolerances, which is a major issue when wall is required to provide groundwater cut-off for multi-level basements as tolerances are difficult to achieve for deep piles, uncertainty associated with the prediction of wall axial capacity as piles are rarely tested, difficulties in using temporary props as wall restraint due to restricted working spaces in urbanised zones and difficulties in adopting ground anchors as restraint due to the existence of adjacent sensitive structures in built-up areas. Such complexities have resulted in cases of failure, non-serviceability and abandonment of basement construction schemes. Therefore, overcoming the intricacies associated with the application of bored pile walls is becoming a priority to the present day basement engineer.This paper is centred on the numerical modelling, design, construction and monitoring aspects of four recent case histories of multi-level basement and marine engineering construction schemes in the United Kingdom and the Republic of Ireland, which involved the use of bored pile retaining walls. The paper highlights the various customised approaches and innovative novel solutions adopted on the sites, to mitigate risks and ultimately overcome the intricacies associated with the earth retention techniques. Simple empirical equations for developing the geometry of secant pile walls for effective groundwater cut-off are presented and validated. An alternative approach for predicting axial capacities of bored pile walls is also presented; this is shown to be considerably less conservative than a common routine design approach, while also in good agreement with observations made in a recent series of laboratory-based scale model tests."

Jan 1, 2017

By Timothy C. Siegel

Accurate representation of the geotechnical resistance distribution is critical in evaluating the performance of piles and pile groups for design. A current practice is to infer the geotechnical resistance distribution based on measured changes in strain during conventional top load pile testing. Especially for drilled and bored piles, the residual load is typically assumed to be negligible both during testing and after the application of the structure load. A practical result is that the compressive structural load is anticipated to be opposed primarily by the shaft resistance with little or no mobilized toe resistance. The predicted top deflection is estimated as the combined elastic compression plus the movement necessary to mobilize shaft resistance. The development of residual load (and associated negative skin friction) results in a significantly different design condition. Negative skin friction tends to force the pile into the ground and develops residual load in the pile that contributes to the internal compressive load. Significant toe resistance can be mobilized in order to resist the combination of negative skin friction and the sustained compressive load. The pile movement becomes a function of the toe penetration required to mobilize sufficient resistance to reach a balance of forces. In an effort to study the development of residual load in augered cast-in place (ACIP) piles, the authors installed and monitored strain gages that were embedded in an 18-inch diameter ACIP pile at a site in southeast Georgia. The results of this study indicate that residual load develops over time and reaches a distribution that is consistent with the principles of the unified design of piles. It is concluded that residual load develops in ACIP piles (as well as all drilled and bored piles by the same mechanisms) and that the residual load should be considered in the interpretation of load tests and in the pile design, particularly in the estimation of the single pile and pile group settlement.

Jan 1, 2009

By Mohamed A. Sakr

An experimental study on the behavior of pile group's arrangement under lateral load was carried out in the level ground and at crest of sand slope 3H: 2V. Tests were conducted on single pile and pile groups with center-to-center pile spacing of 3D. The model piles were founded in sand with relative density 25%. Several configurations of pile groups were used to study the effect of piles arrangement in the group (series or parallel) with respect to slope crest. The behavior of the pile groups in the level ground was compared with the behavior of pile groups at different configurations at the slope crest. Based on the test results, the behavior of laterally loaded pile groups adjacent to a slope crest depends largely on piles arrangement in the group with respect to direction of the lateral load. Pile groups in the level ground have more resistance to lateral loads when they are arranged in a parallel configuration than in a series, whereas the reverse is true in cases of pile groups constructed near to the edge of a slope. It is advisable to use the pile group in series arrangement for groups constructed at slope crest to minimize the effect of the ground slope on lateral capacity of piles and the occurred deflection and maximum bending moment of the lead row in the group.

Jan 1, 2010

By B. Sivarama Sarma, Biswabikash Rout

"Seepage control has to be achieved with plastic concrete cut-off diaphragm walls in dam structures. Materials selected for construction of cut-off walls must be durable, impermeable and have stiffness comparable to the surrounding soil.Plastic concrete provides a feasible and economical solution for construction of durable and impermeable cut off walls for dam structures. Plastic concrete wall should not be understood as a concrete wall with similar mechanical properties of concrete used in buildings, piles and spillways sections. Though it consists of the same materials as those of conventional concrete it has the major differences in end product due to predominant addition of bentonite slurry in the mix with very high water cement ratio. This makes the hardened concrete with very low compressive strength less than 5MPa and high failure deformations after the peak load.This technical paper examines a case study, the typical specifications on demand for construction and the issues corresponding to misunderstanding of the material as a structural grade concrete material. Conclusions were drawn based on a few project site quality data and trial mix experimental data. The anomalies in specifications on demand for construction of curtain wall in a dam structure were removed with modifications.INTRODUCTIONDiaphragm walls which are constructed in trenches made of plastic concrete basically serve the function of seepage control under confined measures. They should have the ability to sustain and undergo large plastic strains as compared to conventional concrete. The three basic mechanical properties of plastic concrete cut-off walls are to have least permeability, minimum strength to retain its shape and ability to undergo large deformations under confined loading conditions. The constituents of plastic concrete are cement, bentonite, coarse and fine aggregates, chemical additives to improve flow of concrete and sometimes to retard the setting time and water."

Jan 1, 2017

By Nadir Ansari, Brian W. Wilson, Marina S. W. Li

"A hybrid Deep Mixing (DM) shoring system was recently constructed for a high-rise development in downtown Vancouver, British Columbia, Canada for the temporary support of a five-level basement excavation. The site is bounded by an existing bridge off-ramp structure along its longest side and by city streets on the other two sides, which formed a truncated triangle in plan. A conventional secant pile wall was installed along the longest side, about 380 ft (116 m) in length, of the site. Hybrid shoring walls (HSW) 1 and 2 were installed along two shorter sides with each being 235 to 246 ft (72 to 75 m) long. HSW 3 completed the excavation support system along the shortest side with a length of about 55 ft (17 m). Cutter soil mixing (CSM) was proposed by the excavation and shoring design-build team in lieu of conventional secant piling. CSM was the preferred method to construct the infill panels between soldier piles because of the speed at which the shoring system could be constructed in the variable fill, peat, wood waste and overburden. Design ConsiderationsTo minimize the impact on buried utilities along the outside perimeter of the excavation, the temporary shoring was designed to limit the lateral displacements to less than 0.8 in (20 mm). Factors taken into consideration for shoring design included the lateral earth pressures from the fill and native soils, groundwater pressures, temporary construction loads (e.g., crane or heavy plant/equipment), and permanent structural requirements. The subsurface conditions at this site typically consisted of fill (cohesive and granular), overlying peat and/or wood waste, overlying clayey silt to sandy silt, overlying weathered to dense to very dense clayey silt till to sandy silt till with silt layers. Localized, perched groundwater was observed within the fill, peat, wood waste and sandy silt layers above the dense till."

Jan 1, 2017

By Tom George

"INTRODUCTIONNo. 1 Queens Rd was an existing 10-storey office building founded on large pad footings. This project involved the construction of a 6-level, 15m (50-ft.) deep basement excavated immediately adjacent to the existing building and also beneath the existing footprint of the Southern end of the building. The total perimeter of the new basement was to be approximately 200m (656 ft.) all with a retained height of 15m (50 ft.). It was also proposed to add a further 5 storeys to the building. Approximately 18 of the existing columns supporting the 10-storey building were to have the applied column load diverted from the existing foundations at ground level onto the new piles or basement raft 15m (50 ft.) below.The geotechnical profile consisted of fill for the top 1.5m predominately comprising of clayey sand with a high gravel content from 1.5m to 9m (5 to 30 ft.), a medium dense to dense clayey sand and then below was a sandy clay extending to 15m (50 ft.) ranging from stiff to very stiff. From 15m on completely to extremely weathered siltstone was encountered. The groundwater was measured at 9.5m (31 ft.) below the natural ground surface.DESIGN BRIEFThe existing building columns were founded on large pad foundations up to 4.4m (14.5 ft.) square, founded on the dense clayey sand. These pads would require temporary support to enable the excavation to proceed beneath them. Upon completion of the excavation under the pads new columns were to be constructed joining into the existing columns to transfer the load onto the new raft slab, 15m (50 ft.) below. The existing 10 floors were to be refurbished. It was planned to undertake all the temporary support and transferring of loads while the structure above was only able to provide a dead load. It was decided that any movement of the building would have minimum impact on a skeleton structure. During the temporary support of the columns, movements due to construction activities had to be monitored to understand any potential stresses in the structure above.The original design required beams to be installed under the pads and supported at either end by temporary piles that were to be founded below the level of the proposed excavation. (Refer to sketch 1). Wagstaff Piling considered that this methodology had difficulties in construction at all stages and did not provide facility for transfer of the load without significant movement of the structure above. Wagstaff Piling revised the design to attach beams to the columns above the pads using shear collars. (Refer to sketch 2). These beams supported on the temporary piles could then be jacked upwards to remove loads off the pads. This would enable removal of the pads with minimal movement of the 10-storey building above. (Refer to photo 1 and back cover photo)."

Jan 1, 2005

By Richard D. Luark, Fernanda S. Madrona

Deep foundation construction in highly developed urban settings pose unique challenges of working with deep excavations in a relatively confined area while preserving the integrity of nearby structures. For construction of the below grade parking for two, 40-story residential high-rise towers, shoring walls were required to support the maximum 70-foot-deep vertical excavation in downtown Seattle, Washington. The design of the excavation support system consisted of soil nails combined with closely spaced vertical elements to allow the top row of soil nails to be installed up to 10 feet below the ground surface avoiding conflicts with adjacent underground utilities. To limit deflections next to a seven-story building, the upper rows of soil nails were post tensioned. An instrumentation program was implemented to monitor the deflections in the shoring walls by means of vertical inclinometers and optical survey monitoring. The shoring wall performance, designed to limit deflection to less than 1-inch to meet the City of Seattle requirements, was validated by the instrumentation program. This paper provides a discussion of the design and construction of the shoring walls as well as the monitoring data collected from the instrumentation system. PROJECT INFORMATION The project consisted of two residential high-rise towers, with five levels of below grade parking, located at 707 Terry Avenue Seattle, Washington. The project site covers a half city block, approximately 120 feet by 240 feet, and is bounded by Terry Avenue to the east, Columbia Street to the north, Cherry Street to the south, and an alley to the West. Prior to the development, site was occupied by surface parking. A 7-story concrete building with two stories of below grade parking, owned by the Archdiocese of Seattle is located just west of the 16-foot-wide alley. Numerous below grade utilities consisting of electrical, telecommunications, gas, water, sanitary sewer, steam, and storm drains, surround the project. The perimeter below grade parking walls extended within inches of the property boundaries. Topographic relief across the site was on the order of 8 feet. Figure 1 illustrates the site plan view.

Jan 1, 2019

By Jørn Thomsen, Christoffer Brodbaek

"As governments increasingly accord high priority to sustainable energy, policymakers are finding that wind energy has a long track record as a proven alternative to conventional energy supply.Over the past two decades, wind turbine projects have been constructed offshore because of more stable offshore wind conditions and because there is more available space for large wind farms out in the open sea. Vindeby Wind Farm in southern Denmark was constructed in 1991. As the world’s first offshore wind farm, it provided valuable information and experience for researchers and designers that have led to new technologies and design improvements, a trend that will continue as more offshore wind farms are constructed. Today, the world’s capacity of the installed offshore wind turbines exceeds 1,000 MW. Most of these are installed in Northern Europe where there was early political support and favorable conditions, such as strong winds and relatively shallow waters. Offshore wind projects are now under development around the globe, including continental Europe, the U.K. and North America. ‘The largest offshore wind farm today is Denmark’s Nysted Offshore Wind Farm, which has a total capacity of approximately 480,000 MWh, equivalent to the yearly consumption of 120,000 households. It is five to six miles offshore in the Baltic Sea in the southern part of Denmark.The owner is a joint venture between DONG Energy of Denmark and E.ON Sweden. Bonus Energy (now Siemens) supplied the wind turbines, and P. Aarsleff A/S and subcontractors supplied the foundations. The contractor’s consultant, COWI A/S of Denmark, developed and designed the turbine foundations. With a total capacity of 165.6 MW, the project consists of 72 Bonus 2.3 MW turbines in water depths up to 33 ft. The turbines have a hub height of 226 ft, and the turbine blade diameter is 270 ft. The rotor and nacelle (the structure that houses the generator, gearbox and other equipment) weigh approximately 150 tons, and the weight of the steel tower is approximately 130 tons. The wind farm site is located in a relatively protected area of the Baltic Sea, but during the winter months, the water often freezes and the foundations needed to be constructed to resist ice forces. The founding soils at the site are overconsolidated clay tills with boulders and with a thin layer of softer surface sediments. Pockets of up to 30 ft of soft sediments were encountered, which required special foundation preparations."

Jan 1, 2009

By Robert A. Field

Static-Load Piledriving utilizes a hydraulic push to facilitate the installation of a pile. The pile is not rotated, impacted or vibrated. A smooth pushing force advances the pile incrementally into the ground. Static-Load devices must have a reaction mass to push against. The most simple form of a Static-Load device is a jack; more advanced equipment, such as the Still Worker, also utilizes this approach. This paper focuses on the use of the Still Worker on three challenging projects. In each case, the existing site conditions made it risky, or unattractive, to utilize conventional impact, vibratory, or drilled-shaft equipment.

Jan 1, 1997

By Peter J. Nicholson

Since the reintroduction of soil mixing to the United States over 10 years ago, the work installed by soil mixing technology has grown dramatically. From an annual turnover of less than ten million dollars per year the volume of soil mixing put in place has grown to an estimated $40 million per year in the year 2000. The majority of work done to date has involved walls, either for excavation support, permanent retaining structures or hydraulic cut-off walls. The other major use for soil mixing has been for mass stabilization of soils whether for isolation of contaminants or for retaining structures. This paper will discuss the uses of and costs of typical soil mix structures. BACKGROUND Soil mixing is defined as the in-situ combining of reagents, typically cement, with native soils, the purpose being to modify or improve the ground. This history of soil mixing covers only the use of cement slurry, aggregated with soil in-situ by mechanical mixing methods only. Soil mixing by use of high-pressure hydraulic means, also known as Jet Grouting, will not be discussed. In addition this will not cover ex-situ (above ground) mixing, or mixing dry reagents with soil. Only mixing applications for building, civil and heavy construction applications will be discussed, with only passing reference made to uses of soil mixing for environmental remediation work.

Jan 1, 2001

By W. L. Chong

For a project located in Docklands Victoria, a high-rise development was proposed where the geology comprised soils of various compositions and consistencies to approximately 50m deep before being underlain by a siltstone bedrock. Due to the structural loads and spatial constraints, the majority of the foundation piles were designed to be socketed into the siltstone. Key factors in selecting the Continuous Flight Auger (CFA) technique as an effective piling solution are explained. These factors included structural and geological considerations, piling rig capabilities, pile testing regime to verify load performance and integrity, the extensive suite of construction quality controls and instrumentation records required while also achieving an appropriate piling budget and program. This paper also described how these factors underpinned the design approach of the final piling scheme. Critical aspects considered during construction and post-construction quality and pile testing records required to meet and satisfy the strict project piling specifications are also presented. The project adopted what may be considered the “best practice” in deep CFA piling. To the author’s knowledge, this project achieved the record for the deepest CFA piles in Australia where multiple piles to 53.8m deep were constructed.

Nov 1, 2022

By Dario Libano, Armando Caputo, Francisco Caputo

"UHE Peixe Angical is a 452 MW hydroelectric power plant located on the Tocantins River in Tocantins, Brazil. In 1999, geologists began feasibility studies to estimate the river’s hydroelectric potential, and the decision was made to proceed with the construction of a power plant. In 2002, after extensive investigation, the studies indicated geological homogeneity at the site for the dam, except for an anomaly detected on the left margin, and construction began on the $1.2 billion project.As the work began, the complex ground conditions presented several serious difficulties. The solution was unlike any undertaken before in Brazil— a 100-m-long secant cutoff wall, with 76 1.8-m-diameter piles of up to 78 m deep. All were placed in a six-month period.In the preparation for the detailed construction plans, further studies in the area of the anomaly better defined the geology so that a treatment program could be developed. The feasibility study had detected silicified rock with high permeability in one area, and an injection curtain was designed with five injection lines. In the other area with an anomaly, further investigation revealed a permeable marble formation that was 50 m thick. Here, a specific injection program with three injection lines was developed.The injections started in February 2005 in the marble formation area. By July of that year, only the primary and secondary holes were drilled from the three lines, resulting in a space between injections of 1.50 m. By the end of July, the drilling was halted. The contractor had identified a thick area of heterogeneous material below the transition zone that was characterized by a mixture of soil, fractured rock and hard fractured rock. The anomalies were detected while drilling, and both the general contractor and the designer concluded that the phenomenon of “piping” was taking place.Constructing a positive cutoff wall became a priority."

Jan 1, 2009

By Robert B. Bittner

The Sutong Bridge across the lower Yangtze River in China will have, when completed, the longest span (1,088 m) and the highest towers (306 m) of any cable stayed span in the world. The foundations for this record setting span will also be record setting. They are located in water depths exceeding 30 m with maximum flows exceeding 3 m/sec. The soil at the site of the main pylons consists of layers of silty sands and silty clays extending to bed rock at 270 m below river elevation. This paper describes the innovative methods used by the team of foundation designers and constructors to support this record setting bridge at this very challenging site. This paper covers three specific topics related to the foundations of the Sutong Bridge: ? Design and construction of the 131 drilled shafts (2.8/2.5 m diameter and 114/117 m long) under each of the two main pylons, including the post-grouting of all drilled shaft tips. ? Design and construction of the scour protection for the two main pylons. ? Construction methods used to construct the waterline pile caps (113.8 m by 48.1 m by 13.3 m deep) under each pylon.

Jan 1, 2007

By J. Nakayama

Construction of foundation piles or diaphragm walls through rocky or boulder containing formations has been long-standing difficulty. It has been widely understood that the down-the-hole hammer is the most capable mechanical means but is restricted in drilling diameter by the unavailability of drillhead sufficiently large diameter and the difficulty of disposal of cuttings. A great number of submersible motordrills have been used for the construction of cast-in-place piles and diaphragm walls and the reverse circulation system employed has demonstrated its advantage of the prompt removal of cuttings. The development of multi-head down-the-hole hammer drill combined with reverse circulation system presents a powerful engineering choice for those "hard-to-drill" ground formations. This paper will introduce the features of the system and some actual operation results in the foundation engineering through those hard rocky ground formation in some countries.

Jan 1, 1989

By Song-yu Liu, Chao Yan, Yong-feng Deng

"In order to investigate the stability of embankment on soft subgrade improved by T-shaped deep mixed column composite foundation, the internal forces and failure modes of columns were analyzed on the shape of critical slip surface and the displacement fields of composite foundation through strength reduction method of three dimensional numerical simulation. Then comparison between T-shaped and conventional deep mixed column composite foundation were conducted. The simulation results indicate that the stability analysis was overestimated by limit equilibrium methods. Piles within the slope shoulder provide great resistance slide effect through the vertical bearing capacity, while the piles nearby slope shoulder and outside slope shoulder providing great moment to resistant slip. The embankment stability of T-shaped deep mixed column composite foundation is higher than that of conventional deep mixed column composite foundation while cost less cement and construction time.INTRODUCTIONThe soft soil has many unfavorable project properties such as high compressibility, low strength, and high water component. Embankment built on the soft soil will face subsidence, horizontal displacement and stability problems. Cement-soil deep mixed column composite foundation is more commonly used as a method for construction of embankment on soft ground [1-2]. For the existing problems of China's current cement-soil pile (wet jet mixing pile), including strength uneven, effective treatment with shallow depth and high cost, a new technique, T-shaped bidirectional deep mixed column, is introduced [3]. An automatic expanding mixing blade was developed by Liu et al. shown in Figure. 1, to install TDM columns [4].T-shaped deep mixed (TDM) column combines bi-directional deep mixing technique and T-shaped deep mixing technique: ?Using concentric biaxial drill pipe, opposite rotational direction of the blade on the inner drill pipe and the outer drill pipe. By squeezing action of the blade on the outer drill pipe, forward and reverse rotation of the blades bidirectional mixing at the same time, blocking the way to take the grout, the uniformity of cement mixing is improved. ?Scalable stirring blades, which can be stretched for two different radius at any depth below ground, expand cross-section of the upper pile (enlarged head), forming expanding cross-section within the upper part of a certain depth which is similar to the shape of nail. As a new composite foundation, T-shaped mixing pile composite foundation is widely applied. However, studies on the stability of T-shaped column treated soft subgrade are rare in the research. So the stability study on T-shaped column composite foundation under embankment for guiding the design and construction has important significance."

Jan 1, 2015

By Peter Faust

The foundations for the new South Viaduct Bridge in San Francisco were extremely challenging due to the requirement for very large and deep piles installed adjacent to historic structures. Drilled shafts up to 12? foot in diameter were constructed to a maximum depth of 200? feet in alluvial soils and Franciscan Bedrock using an oscillator system for the installation of the permanent steel casing. This paper provides an overview of the construction techniques, the equipment, and the challenges associated with constructing 12? foot diameter shafts on this very complex project in one of the nation?s nicest landscape setting.

Jan 1, 2011

By Andreu J. Ferrero

Polyurethane and acrylate resins are routinely injected into soils to gain strength and control water flow. However, most published data regarding strength gain is derived from laboratory samples created under ideal conditions. This study endeavored to inject resins into full scale mock-ups that could then be excavated and tested to yield results comparable to actual field conditions. To achieve this goal, a large container was filled with a silty SAND (SM), as defined by the Unified Soil Classification System (USCS). The soil was moisture treated and compacted in lifts of 0.3m. PVC pipes installed in a diamond grid into the soil were used to inject polyurethane and acrylate resins. Dynamic cone penetrometer (DCP) tests were conducted on the polyurethane treated soils, the acrylate treated soils, and the baseline untreated soils in the container. Testing results will be correlated to SPTn and CBR values to evaluate increases in the soil strength parameters in the treated soils. Cored samples of polyurethane and acrylate treated soils will be tested in compression, shear, and triaxial. These laboratory test results will focus on material property gains for the treated soils, in comparison to standard values for similar soil types. Complete documentation of the soil type, compaction methods, injection methods, and testing performed have been documented and will be presented in the final paper.

By V. A. Sernov

"One of the ways to increase the bearing capacity of a piled foundation is to take into account soil resistance in the base of the raft. Piled raft is similar to shallow foundation and can transfer significant part of the load into the base. It allows reducing number of piles in the foundation or shortening their length. As a result building terms and foundation costs reduce considerably. However, nowadays in Belarus there is no reliable and suitable in design practice methods of calculation of piled-raft foundations. In order to devise such methods we have analyzed the results of piled foundation tests fulfilled by various authors up to date and have carried out series of field and laboratory investigations in Minsk. The most important results of the investigations are provided in the article. Methods of analysis of piled-raft foundations are described.INTRODUCTIONPile foundations of late years are used extensively in connection with the increased number of storeys and load increment on the soil. Often pile foundations are applied in comparative favorable ground conditions at the surface of the base. In such cases the increase of the bearing capacity of foundations and the reduction of construction cost are questions of primary importance for designers. One of the ways to increase the bearing capacity of a piled foundation is to take into account soil resistance in the base of the raft. Piled raft is similar to shallow foundation and can transfer significant part of the load into the base. It allows reducing number of piles in the foundation or shortening their length. As a result, building terms and foundation costs are reduced considerably. However, nowadays there is no reliable and suitable in design practice methods of calculation pile foundations with bearing rafts. In order to devise such methods we have analyzed the results of piled foundation tests fulfilled by various authors up to date and have carried out series of laboratory and field investigations.Long before the constitution of the first piled-raft foundations in the Soviet Union there were attempts to consider soil resistance in the basis of isolated and strip grillages. Such bases can be considered as separate fragments of the piled-raft foundation. Prof. A. A. Bartolomey had tested more than 70 pile foundations of natural size in different ground conditions. The length of piles was 3 12 m (?????????? 1995). The observed results show that the raft carries about 10 12% of the total load applied when length of piles is over 9 m and space between piles is a=3d. Bearing capacity of the raft is about 35 40% when the length of piles is 5 8 m and a=6d. Prof. Golubkov has tested 2 prismatic piles (cross section: 350x350 mm, L=3800 m) and 2 pyramidal piles (cross section: head - 600x600 mm, foot – 100x100 mm, L=3000 m). One of the piles was tested with a raft and the other one without a raft. Significant influence of the raft on total bearing capacity was determined, the more the settlement was the more it influenced on the raft. Bearing capacity of the raft was 27,5% in foundation with prismatic pile and 42% with pyramidal pile (???????? et al. 1971)."

Jan 1, 2016