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By Aly M. Mohammad

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

Jan 1, 2003

By 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

By Eric Brandner

Expansive soil formations can be found throughout the United States. When subjected to wetting, many of these formations have the potential to swell and exert large uplift forces which can significantly damage lightly-loaded structures. Designing an economical foundation that can resist uplift forces is critical to prevent damage to these structures. The current solutions to control uplift due to swelling soils, such as over-excavation and replacement of the expansive material, or drilled shafts, can be costly and problematic. Piles made from recycled polymer materials may provide a solution. Due to a lower coefficient of friction along the interface than piles made from traditional materials, solid recycled plastic piles can allow expansive soils to move nearly independently from the pile when wetted. This results in a much smaller magnitude of uplift force being transferred to the structure which minimizes the risk of significant structural damage. This paper presents the preliminary results of research conducted on the use of recycled plastic piles in an expansive shale environment. The preliminary phase of the project involved the installation of six 13 in. (330 mm) diameter recycled plastic piles at a test site on the South Dakota School of Mines and Technology campus. The piles varied in length from 15 ft. to 25 ft. (4.6m to 7.6 m). Two of the piles were subjected to a full-scale compression load test in order to determine ultimate capacity, while the additional four piles are being subjected to long-term monitoring of uplift movement. A cast-in-place concrete pile, with a diameter of 6 in. (152 mm) and length of 15 ft. (4.6 m), was also installed at the test site for monitoring. The preliminary results indicate that the use of solid recycled plastic piles is a viable alternative for support of lightly-loaded structures in expansive soil environments.

Jan 1, 2009

By Ambarish Ghosh, Subhaprasad Chakraborty

"Construction of basement floors has become necessary to meet the requirement of parking in office and residential complexes and in hospitals for radiotherapy treatment. Important projects coming up in Kolkata are mostly in closer proximity of residential buildings, office buildings and historical monuments. Sheet piling is mostly used as temporary shoring system during construction. Deep excavation in urban environment creates great problem related to construction induced vibration due to driving of sheet piles for basement, pile driving etc. which raises the chances of damage of adjacent buildings and nearby structures. Vibratory sheet-pile driving is the most common method of sheet pile installation. The knowledge of induced vibration due to this phenomenon is still very deficient. This paper presents the analysis of measured vibration data collected from different sites of Kolkata with varying soil profile. Typical two case studies of sheet pile and pile driving has been presented and the vibration values are analysed. The responses of the vibration are reported in terms of peak particle velocities (PPV). To evaluate the effects of vibration due to pile driving two aspects have been considered: the effect of the energy entering the ground from the pile and the effect of the soil condition.INTRODUCTIONIn urban areas infrastructure development projects are mainly located adjacent to existing structures like residential buildings, offices and historical structures. The construction work of such project influences the surrounding environment as well as human perception (Wiss 1981). During the construction of basement for residential complexes and hospitals sheet piling is mostly used as temporary shoring system or as to support the earth mass. The vibration induced due to driving of piles and sheet piles have been presented herein. Deep excavation projects close to existing structures increase the concern of environmental impact. For this reason the vibration assessment and prediction has become a subject of great interest. It is important to develop a site specific model for predicting the ground vibration resulting from pile and sheet pile driving at the construction sites. The developed model gives the efficacy to guide the engineer to select the construction methodology ensuring the safety of the surrounding structure. The model developed here is site specific and the parameters that has been used are dependent on the soil condition and the energy source."

Jan 1, 2015

By Jinung Do, Sung-Ryul Kim, Juhyung Lee

"Model tests have been performed to investigate the vertical, horizontal and cone tip resistances of bucket pile embedded in sand by different installation methods; suction force by pump and jacking force by actuator. Micro-cone penetrometer is used to evaluate the variation of the effective stress inside and outside of the pile after installation. As a result of vertical pull-out test, the jacked pile shows 3 times larger resistance than the suction-installed pile. For horizontal pull-out test, the ultimate horizontal capacity and the slope of load-displacement curve on the suction-installed pile decreases by 22% and 40%, respectively, compared to the jacked pile. In cone penetration test, inside cone tip resistance of the suction-installed pile is about 40% smaller than the jacked pile, which indicates that the effective stress is reduced due to upward seepage of bucket pile in sand by suction force. Therefore, installation methods can affect the behavior of the bucket pile significantly.INTRODUCTIONA suction force occurred when bucket pile penetrates into sandy soils induces seepage flow into the bucket pile so downward seepage near the outside of bucket pile causes to increases the effective stress, while upward seepage inside the bucket pile decreases the effective stress (Mahn, 2005; Fig. 1). The effect of induced seepage causes to reduce the penetration resistance during installation. On the other hand, reduced effective stress can decrease the horizontal and vertical capacities of bucket pile by significant disturbance at the tip of the bucket pile due to the flow net. Due to the complexity and difficulty considering the effects of suction installation, many previous researchers generally have neglected the effect of suction installation in their experiments. Therefore in this study, the effects of suction installation on resistance of bucket pile is examined."

Jan 1, 2016

By Lucian L. Bogdan

"SummaryActive loaded strand anchors are often used for slope stabilization, retaining walls or tiedown anchors. Normally, strands are tensioned against the structure and wedges are locked inside the anchorages at a certain lock-off load. During the life of the structure, anchors can receive additional loading during a surcharge, seismic event or other activity on the structure.In order to have a reliable ground anchor system, the strand must not slip through the anchorage wedges during its service life. Strand slippage has been reported during lock-off, when dirty wedge plates and wedges have been used. Low lock-off loads are believed to contribute to strand slippage too. Since the initial lock-off load for a ground anchor is usually lower than the lock-load for an equivalent capacity tendon in other types of post-tensioning construction, there is a concern that strand slippage may occur if the load on the anchor increases above the initial lock-off load.Corrosion protection grout, placed after the anchor is locked off, fills the pocket and surrounds the strand and wedges. Some anchor installers believe that the grout will prevent the anchorage from developing additional capacity if the load increases above the initial lock-off load.The load-carrying capacity of an anchorage depends on several factors. Most important are: initial applied load, anchorage geometry, friction between wedge-anchorage-strand and condition of the contact surfaces.The ADSC Anchored Earth Retention Committee considers that the industry should know how wedges behave once the permanent strand anchors are stressed and grouted inside the transition pipe, between wedges and inside the grout cap."

Jan 1, 2005

By Dave Paul

Dam rehabilitation involves a range of design, construction, and operation risks, some of which are not encountered in new dam construction. These risks can have significant impact on project schedule and project budget. Owners, engineers, and contractors need to understand these risks. Existing dams typically were designed in an era of design and construction standards that have been upgraded and changed. Modern standards will impact the construction approach taken and involve understanding the earlier standards. Knowledge of historical standards/practices as well as current design standards and construction methods is valuable for developing and designing rehabilitation components. Construction records and as-built drawings are valuable when they are available. Rehabilitation projects often consist of older projects where as-built documents or construction records are not available. Where these records exist, many (most) times, they do not fully reflect the current conditions within the dam and appurtenant works. leading experienced practitioners to “expect surprises” both during investigation of the existing facility, as well as during construction. “Surprises” should be expected even when historical records of investigations, design and construction are available. Unknowns, be they known unknowns or unknown unknowns, can be planned for by developing an approach for the design and construction process to identify potential issues/problems, or at least alert the designer and contractor of potential issues. A Risk-Based approach applied for the entire life of the rehabilitation project can be used to alert the parties of potential “surprises” and provide direction for mitigating issues as they arise. This type of approach is particularly effective when the process includes senior practitioners with decades of design and construction experience in all aspects of dams. Minimizing impacts created by “surprises”, particularly during construction, can result in an improved project meeting budget and schedule goals and design standards. This paper identifies and categorizes risk types salient to dam construction, reviews the process of risk identification and analysis, discusses guidelines for risk allocation, reviews strategies to mitigate risks, presents several case studies where risk mitigation strategies were employed successfully (or unsuccessfully), and presents lessons learned. The paper concludes with a summary and recommendations for best practices for Project Risk Management and mitigation that can be used by: Owners; Design Engineers; and Construction Managers, in planning, design, pre-construction and construction phases of dam related projects.

By Gregory A. Stephan

A case history of design, prediction, instrumented static load tests on probe piles, installation monitoring, and integrity testing of production piles is presented. Based upon project-specific subsoil conditions, as obtained from several 60 to 80 ft (18.3 to 24.4 m) deep test borings, deep foundation system alternatives included driven concrete and steel pipe piles as well as augered cast-in-place (ACIP) piles. High structural loads, site-specific constraints, and the production time frame mandated by the project owner led to the selection of an ACIP pile foundation system that was designed for a pile capacity of 75 tons (667 kN) in compression and 35 tons (309 kN) in tension. Site-specific concerns were raised about the highly porous nature of fragmented and decomposed sandy limestone as well as the high grout intake during construction that could result in increased foundation cost as well as interconnecting of the piles in the rock layer. Consequentially, a multi-phase ACIP pile evaluation program consisting of instrumented compression pile load tests, in conjunction with single-hole ultrasonic pile testing, pile echo testing (sonic testing), as well as full-time production pile monitoring by an experienced geotechnician was specified. As a result of this testing and evaluation program, while grout usage was determined to be within an acceptable range, the instrumented compression load tests yielded data that allowed use of 55 ft (16.8 m) long ACIP piles in lieu of the original plans to use 70 ft (21.3 m) long precast concrete piles. This information was effectively utilized as part of the overall quality control program to install a total of 268, 14 in. (356 mm) diameter ACIP piles within the building footprint to depths of 55 ft (16.8 m) below the pile cut-off elevation as part of the foundation support system. Information recorded during installation included rate of insertion/extraction of the auger, grout pump strokes and pressure, total grout volume, and grout factors, as well as quality and strength of grout. Additionally, many pre-selected installed piles were tested for integrity with a Pile Integrity Sonic Analyzer (PISA) using both sonic and ultrasonic methods. This engineered, monitored, and tested foundation solution provided an effective and quality intensive basis for completion and approval of the foundation work for the building that resulted in cost savings over other foundation alternatives for the owner.

Jan 1, 1999

By Saba Mohan

For the three full-scale pile installations, two different high-energy hydraulic hammers were selected for the installation. However, these hammers may not have sufficient energy to drive these large diameter piles at their ultimate capacity following long-term set-up. Nevertheless, these hammers were selected because, soil plug behavior, the generation of excess pore pressures and remolding of soil during driving were expected to reduce the shaft and end bearing resistance, and therefore reduce the energy required to drive these piles to design penetration. Data collected during continuous installation driving and after a series of re-strikes at different set-up times ranging from 1 to 33 days were used as input data for CAPWAP analyses. These results were used to estimate the soil resistance along the pile length and at the toe of the pile, and the soil pile set-up behavior. Validity of the procedures used to predict the soil resistance to driving and predicted blow counts were verified with the field observed blow counts and the energy that was delivered to the pile. Based on combined CAPWAP analyses, the soil pile set-up with time was predicted.

Jan 1, 2002

By Hiren J. Shah

Across much of New York City, the geology of glacially deposited soils follows a common sequence. Outwash sands generally overlie varved silts and clays, which lie above a basal till deposit underlain by the bedrock. Pile foundations at projects with such typical stratigraphy generally develop their axial capacities by extending below the fine-grained deposits into the till or the bedrock. Contrastingly, at a project site on the Brooklyn waterfront, high capacity piles were efficiently and economically installed by driving them into the relatively shallow glacial drift and till deposits which lay above thick fine-grained compressible glacial lake deposits. An unusual aspect about the foundation design at the Brooklyn project site is that, relatively short and high capacity piles were driven into the shallow glacial drift and till deposits, overlying the thick fine-grained glacial lake deposits. In order for this unusual foundation scheme to be feasible and economical, the piles needed to achieve their driving criteria in the upper strata. Consolidation settlements in the lower stiff and over-consolidated glacial lake deposits below the pile tips had to be relatively small. The paper discusses the unusual stratigraphy in this area of Brooklyn in greater detail with geologic profiles and engineering characteristics of the glacial strata. It also discusses the design aspects of the pile foundations, settlement estimates, a pile drive test program during design, results of the static load test program during construction, and production pile installation results.

Jan 1, 2008

By Ahmed Elmekati, Frederick C. Rhyner, Steven R. Lowe

"The current phase of the Pacific Park development (formerly, Atlantic Yards) in Brooklyn involves constructing buildings on a platform over an existing LIRR rail yard. To preserve the maximum amount of space in the already congested yard and protect the yard which remains in service during construction, high capacity foundations are being designed well above previous capacities in the area. In addition to spread footings and small mats, various diameters of drilled piles are being used at design capacities ranging up to 600 tons. The piles are generally grouted at low pressure, up to about 50 psi. Load tests for various drilled elements, including piles, tiedowns and soil anchors, have confirmed allowable side resistance (bond) stresses in dense sand ranging from 20 to 30 psi. Testing with different rigs and operators has shown that down-the-hole hammers are feasible, but the installation techniques, types of equipment and size of the pile make a significant difference. The results show that more cost-effective foundations are possible when ample testing confirms expectations.I INTRODUCTIONThe Long Island Rail Road has operated a mainline on Atlantic Avenue since the 1800s, with a terminal at the intersection of Atlantic and Flatbush Avenues. In the early 1900s, the mainline was reconstructed in a cut and cover tunnel section. The LIRR’s Atlantic Yard was constructed circa 1908 to service the terminal. It was depressed about 25 feet below street grade to coincide with the LIRR’s mainline tunnel under Atlantic Avenue. Record drawings indicate that the gravity retaining walls lining the perimeter of the yard and other ancillary structures had been designed for an allowable bearing pressure of five tons per square foot (tsf). Perhaps by coincidence, the mat foundation for the tower of the Williamsburg Savings Bank was also designed for five tsf in 1929.Figure 1 shows a typical geologic section through the site. The geology and subsurface conditions in this part of Brooklyn consist of fill generally five to 20 feet deep underlain by dense to very dense sand and gravel; in places, with numerous cobbles and boulders which make pile installation challenging. The sand strata that are on the order of 150 to 200 feet thick were laid down by glaciers during the last ice age and have been heavily precompressed. The sand strata are underlain in places by remnants of the Cretaceous-era Raritan Clay formation and Fordham Gneiss bedrock. Because of this, the sand strata generally provide excellent support for shallow foundations and the allowable bearing of five tons per square foot is usually easily justified."

Jan 1, 2016

By Glenn J. Rix, Eduardo Tavera, Raphael Siebenmann, Zhongjie Zhang, Robert C. Bachus, Jongwon Jung

"The Louisiana Department of Transportation and Development (LADOTD) uses a variation of the FHWA-modified Gates equation to verify the nominal pile bearing resistance, typically on smaller projects where static load tests and dynamic monitoring are not practical. An inconsistency in the resistance factors for load and resistance factor design (LRFD) penalizes the target pile capacity needed during field observation if the LADOTD dynamic formula equation is used, which is unreasonable, and has created confusion among designers, consultants, district personnel, and inspectors in Louisiana. The objectives of this project are to recalibrate the FHWA-modified Gates equation and update the associated LRFD resistance factor for pile types and local soil conditions encountered in Louisiana. Improved consistency relative to the current design approaches will be achieved if the updated resistance factor matches or exceeds the worst-case resistance factor used by LADOTD, which will reduce confusion among users. Updating the resistance factor will also serve to increase confidence in the FHWA modified Gates equation, optimize the efficiency of the piles, and reduce project costs.IntroductionThe original 1957 Gates pile driving formula (Gates, 1957) is an empirically derived dynamic formula that is used to predict pile capacity in the field during pile installation. The original Gates formula tends to over-predict pile capacity for low driving resistances and under-predict pile capacity for high driving resistances (Hannigan et al., 1998). Thus, the Federal Highway Administration (FHWA) proposed a modified version of the Gates formula that addressed this limitation. The FHWA–modified Gates equation is:"

Jan 1, 2017

By Dale E. Berner

A new navigation dam at Olmsted on the Ohio River will be built "in-the-wet" using a lift-in construction method by the Washington Group/Alberici Joint Venture for the U.S. Army Corps of Engineers, Louisville District. Up to 4,000-ton precast concrete dam shell segments will be prefabricated on the Illinois riverbank and lowered into the river on a marine skidway and cradle. A 4,500-ton capacity catamaran crane barge will lift the precast concrete shells and lifting frames from the cradle, and transport them partially submerged to a piled foundation pre-installed underwater. Tremie concrete will be used to compositely connect the shells, piles and sheet pile cut-off walls. This paper focuses on the pipe-pile foundations for this half-mile long navigation dam, and for the temporary precast yard and marine skidway. The dam foundations are designed to resist large ground motions from the New Madrid Fault Zone, and selected production piles are designed to serve as landing piles to support the shells during the construction process. Specific foundation issues addressed in the paper include: pile load tests; production field testing requirements; controlled fixity 24-inch diameter pipe-pile design including seismic considerations; cut-off wall design; sheet pile cellular fixed weir design; isolation jOint design; and temporary works foundation designs for both the precast yard and the marine skidway, including testing of 42-in diameter pipe piles.

May 11, 2007

By David Coleman

This paper presents a case history involving the installation of drilled in piles with rock sockets for the Bicycle and Pedestrian Path project located west of the Henry Hudson Parkway within the Riverside Park between 83rd Street and 91st Street at the Hudson River in New York, NY. The paper specifically addresses access and construction procedures for a marine installation when working in an urban and environmentally sensitive setting.

By Daniel Ruffing, Charlie Krug

In recent years, the chain-style trencher has been proven a valuable tool for installing vertical walls on challenging sites where conventional methods may be less desirable. Like many tools, trenchers are most effective when used with the right application. Trenchers are commonly used for applications that could also be completed with conventional slurry trenching; low-permeability cutoff walls, collection trenches and permeable reactive barriers (PRBs). Drawing from a wealth of experience with conventional slurry trenching and the trencher, this paper compares and contrasts the technical considerations, treatability, installation, performance, and lessons learned for recent projects.

By Marcelo Chuaqui

We certainly have the data to back calculate it. I must admit that I haven't, at the moment my priority is not on what is the stiffness of the jet grout but is making sure that the jet grout is really there. It's a bit like what Stuart Littlejohn was talking about this morning in terms of grouting on the dams a small window causes a big problem so it's having the jet grouting there at all, at the moment must have been my focus rather than just what is the stiffness once you've got it there.

Feb 10, 2003

By Josef K. Alter

Long-term performance and behavior of post-tensioned ground anchors subjected to axial cyclic loading constitutes an important aspect of the stability, reliability and overall performance of wind turbine deep foundations. Axial cyclic loading of post-tensioned (PT) ground anchors in soils has not been thoroughly investigated as evidenced by the research conducted for this topic. This paper evaluates research test data, available literature, and industry expert opinion on the current status and problems of deep foundation post-tensioned ground anchor (PTGA) technology, as applicable to the wind energy industry. It also introduces a proposed design solution that addresses the problems of construction cost and long-term performance of wind turbine deep foundations in soils subjected to dynamic cyclic axial loading. Deep foundations using ground anchors for wind turbines have only recently gained attention as a possible viable alternative to the mass spread footings currently in use. One of the primary problems with general acceptance of current PTGA designs is the need for long-term anchor maintenance. The research that was conducted for this study indicates that current literature only partially addresses the many factors influencing load capacity and pullout performance of ground anchors. The lack of information indicates the deep foundation industry has fallen behind in designing and implementing new technology to improve safety and performance, ensure sustainability, reduce costs, and address environmental responsibility. This paper describes the significance of this problem as it applies to the wind energy market, and proposes a new technology solution. The research, expert opinion, and analysis presented by the author is used to support the premise that ground anchor construction cost and long-term maintenance can be reduced with PTGA systems using the Con-Tech Systems (CTS) patent-pending Groutable Void Form (GVF) technology.

Jan 1, 2010

By Jesús E. Gómez

A recent bridge underpinning project provided a unique opportunity to obtain information on the load-deflection response of 260 hollow-core bar micropiles. All production micropiles were proof-tested to a maximum load of 125 percent of the design load. In addition, four verification tests were performed on sacrificial micropiles to at least two and a half times the design loads. This paper presents the results of the verification and proof tests performed for this project, and provides recommended values for design of hollow core bar micropiles in soils similar to those encountered. This work shows that hollow core bar micropiles provide a significant unit bond capacity in both granular and fine soils, which may be greater than that typically expected in pressure-grouted (Type B) micropiles. The hollow core bar system allows faster installation rates in the soil types encountered than other traditional micropile techniques, and can be installed with relatively simple quality control procedures.

Jan 1, 2007

By Serge Borel

An efficient design method is proposed for "piled-footing" and "piled-raft" foundation under lateral loads. It combines the methods used for the displacement design of shallow and deep foundations and takes into account the interactions between the piles and the cap or raft. This method has been applied to previous full-scale tests carried out in the United States. Two groups of six instrumented driven piles were laterally loaded several times: first with the concrete pile cap in direct contact with the soil, and then, after a thin layer of soil had been removed beneath the cap. The proposed method models well the real behavior of piled-raft foundations. It highlights the positive effect of the cap in contact with the soil, which reduces significantly the displacements and the maximum pile bending moments. These are divided by two for the analyzed case histories.

Jan 1, 2002

By Pier Luigi Iovino

As Technical Director of the Naples, Italy based Fondedile, a geotechnical construction firm specializing in static restoration of structures, Fernando Lizzi, Ing., devoted over 30 years to the pursuit and advancement of static restoration and subsoil strengthening. Seismic events, construction of new structures on polluted and/or unstable soils in urban areas, and a need to carefully preserve and restore delicate, war-damaged historical structures, manifested the need for underpinning projects. Traditional construction methods and approaches, such as underpinning with additional foundation masonry, were not suitable and would have further jeopardized the stability of the structures. The introduction of the palo radice (root pile) revolutionized the field of underpinning. At the time of the first application of micropiles, the industry standard was driven piles. The drilled micropile was conceived and first implemented in the early 1950s, as an innovative means to underpin sensitive, historic structures and structures in urban areas. Specifically, the new construction technique was conceived as a less expensive alternative, designed to accept structural loads, be installed in limited access areas, in varied working and sub-surface conditions, which did not involve changing soil characteristics, and had minimal disturbance to the structure being underpinned, or to adjacent structures.

Jan 1, 2003