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To investigate the behavior of X-section cast-in-place concrete piles (XCC pile), a series of static load tests for piled foundation are conducted on the basis of a soft soil reinforcement engineering for a sewage treatment plant in the north of Nanjing, China. The testing results are presented in load-settlement curves, pile-soil stress ratios, distributions of skin friction (side friction) and axial force, and load-sharing between side resistance and end-bearing capacity. Comparative analysis between an XCC pile and a circular section concrete pile (circular pile) with the same cross-sectional area indicates that the XCC pile with its increased perimeter can improve the vertical-bearing capacity by 20% because of the larger skin friction. Also, the XCC pile shows increasing pile-soil stress ratio and reduces settlement. The existing design standards for traditional piles can be referenced by the XCC pile composite foundation, because the axial force and skin friction distribution are the same as those of the traditional pile. It has been found that pile spacing is an important factor for XCC piles, and the XCC pile should be considered as a special friction pile because of high skin friction sharing. Above all, the XCC pile can significantly increase ground-bearing capacity. [ABSTRACT FROM AUTHOR]

Meshfree method is one of the numerical methods that typically use higher-order approximate functions and a weighted-residual approach to formulate the shape functions that are independent of the grids. In this paper, a series of computational modeling were conducted using the meshfree local Petrov-Galerkin (MLPG) method to evaluate the bearing capacity and response behavior of extended-length piles. The computational program codes and boundary conditions were generated based on the elastic-plastic behavior of the surrounding soil, reinforcements, and the noncontinuous interfaces between the piles and the soil. Compared to the traditional finite-element method (FEM), the MLPG exhibited higher accuracy in the results and indicated that the optimal length of the pile is directly related to the stiffness of the soil, i.e., the stiffer the soil, the longer the allowable pile length. Overall, the MLPG meshfree method was found to be a reliable and potentially promising numerical method for studying the bearing behavior of pile foundations. [ABSTRACT FROM AUTHOR]

In this study, three-dimensional finite element models, incorporating an elastoplastic material model coupled with isotropic simple softening law, nonassociated flow rule, and shear-band effect, are validated for the evaluation of the shape effect of the square and rectangular vertically uploaded anchor foundations embedded in dense Toyoura sand with embedment ratio of 2 and width of 50 mm. The proposed numerical model has closely predicted experimental uplift load-displacement relationships. The shape effects on the results are also discussed in relation to the progressive failure around the foundations and the shape of the failure boundaries on the ground surface. [ABSTRACT FROM AUTHOR]

Anchor foundations of various embedment ratios, shapes, and sizes are frequently used in civil engineering structures to provide uplift resistance. Therefore, to achieve economic and safe design of such foundations, engineers should understand the failure mechanism associated with them. In the present study, a three-dimensional (3D) finite element model incorporating an elastoplastic material model coupled with the isotropic strain-softening law, the nonassociated flow rule, and the shear-band effect, is used to investigate the failure mechanisms of vertically uploaded shallow rectangular anchor foundations buried in dense Toyoura sand. Satisfactory agreement was found between the experimental and numerical uplift resistance-displacement factor relationships. In particular, the peak uplift resistance, response stiffness, and passive plastic zone development are found to be functions of the embedment ratio, shape, and size. However, previous design approaches cannot capture the size effect on the peak uplift resistance factor of the rectangular anchor foundation. [ABSTRACT FROM AUTHOR]

Changes in geosynthetic clay liner (GCL) properties over time are examined for the case in which the GCL (1) rests directly on a Ca++ rich soil (1,700-1,800 mg/lCa++) and (2) a 30 cm foundation soil (200-300 mg/lCa++) overlying the Ca++ rich soil. Results for a control case in which the GCL rested only on the foundation soil are also reported. The moisture content increased to 108% and then remained constant in the control case. The moisture and calcium uptake from the underlying soil caused the moisture content of GCL to increase to 96 and 86% in the first 279 days of the experiment for the cases with and without foundation soil, respectively. The moisture content then decreased to 80 and 67% after 1,100 days under isothermal condition with and without the foundation layer, respectively. After 1,100 days (three years), the hydraulic conductivity of the GCL increased (attributable to cation exchange) from approximately 3×10-11 m/s initially to approximately 7×10-11 and 2×10-10 m/s with and without the foundation layer. Changes in swell index (SI) and exchangeable cations were measured and correlated to changes in hydraulic conductivity. [ABSTRACT FROM AUTHOR]

During the past few decades, soil nailing has been widely used for stabilizing slopes and excavations. The nail-soil interface shear resistance in the passive zone of a slope or excavation is a critical parameter in design. In this paper, an analytical study is proposed to investigate the progressive pullout response of a soil nail. Pullout process is divided into three typical phases: (1) the initial pure elastic phase during which the nail-soil interface follows a linear elastic stress-displacement relationship; (2) the elastic-plastic phase during which a transition point presents dividing the elastic and plastic zones; and (3) the final pure plastic phase. A comparison study between calculations and laboratory test data are presented to examine the effectiveness of the method. In addition, a comprehensive parametric study is performed to assess the effects of several key factors on the pullout resistance of a soil nail. These factors include the length and diameter, length of plastic zone, and the elastic modulus of a soil nail. Main research findings are presented and discussed to gain a better understanding of the progressive interaction between soil and soil nail. [ABSTRACT FROM AUTHOR]

A capillary barrier as a cover system is a two-layer system of distinct hydraulic properties to prevent water infiltration into the underlying soil by utilizing unsaturated soil mechanics principles. This paper illustrates the application of the capillary barrier system on a slope that experienced shallow slip failures to prevent future rainfall-induced slope failures. In this study, the capillary barrier system was designed as a cover system for residual soil slopes with a steep slope angle under heavy rainfall conditions of the tropics. The capillary barrier system was constructed using fine sand as the fine-grained layer and granite chips as the coarse-grained layer. Both layers were contained in a cellular confinement system. The slope was instrumented with tensiometers and piezometers. The tensiometers were installed at different depths from about 0.5 m to 2.0 m below the slope surface. An adjacent original slope without the capillary barrier system was also instrumented using tensiometers to investigate the performance and effectiveness of the capillary barrier system in reducing rainwater infiltration and maintaining negative pore-water pressure in the slope. The detailed installation of a matric suction measurement device is discussed comprehensively in this paper. The measurement results showed that the capillary barrier system was effective in maintaining the negative pore-water pressures during rainfalls, particularly on the crest of the slope. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of the behavior of an eccentrically loaded model ring footing resting on a compacted replaced layer of sand that overlies an extended layer of loose sand. Particular emphasis is placed on the potential benefits of reinforcing the replaced sand layer with geogrid reinforcement. Load configuration was designed to simulate ring footings under vertical loads and overturning moment caused by lateral loads. Several configurations of geogrid layers, number, and stiffness were used to study ring footings with different inner-to-outer-diameter ratios and load eccentricities. The effect of the depth and the relative density of the replaced sand layer was also investigated. Test results indicate that the behavior of an eccentrically loaded ring footing significantly improves with an increase in the depth and the relative density of the replaced compacted sand layer. However, the inclusion of soil reinforcement not only leads to a significant reduction in the depth of the replaced sand layer but also causes a considerable increase in the bearing capacities of the eccentrically loaded rings, leading to the cost-effective design of the footings. On the basis of the test results, the effects of different parameters are presented and discussed. [ABSTRACT FROM AUTHOR]

The construction process can greatly affect a concrete pile's structural performance. Poor decisions concerning a pile's foundation may result in these important structural elements being unsafe so that strengthening interventions may be needed in the future. In extreme cases, the structure may even collapse. The choice of the most suitable construction process is usually a matter for the company constructing the piles and tends to be based either on previous experience or simply on the equipment available at the time. The parameterization model described herein has been devised to induce good construction practices. It includes several factors related to each construction process, and it could influence the structural behavior and durability of concrete pile foundations. The software application combines the input data from a given construction works with a database whose decision parameters are defined. It has been customized for Portugal and is based on expert knowledge acquired from some of its largest construction firms. It gives the most suitable construction process as the output plus a list of reasons for the decision. It also establishes relationships between the result and a second database that compiles the costs and the duration of the selected process, which are essential data at the predesign stage. [ABSTRACT FROM AUTHOR]

Reinforced masonry block retaining walls are comprised of a narrow column of stacked blocks at their exposed end. This column is placed on a nonstructural leveling pad to facilitate the placement of facing units. Theoretically, this column can generate very large toe resistance to sliding. A recent publication indicates that an accepted design methodology implicitly counts on this resistance in assessing the reinforcement load. Although not calculated in this design, it unconditionally considers that over 60% of the resultant horizontal force in a 12-m-high wall is carried by the toe, which is made up of 0.3-m-deep blocks. This paper elucidates this issue by explicitly identifying the magnitude of toe resistance and critically reviews whether such high resistance is universally suitable for design. It shows that high toe resistance may not be feasible for most foundation soils. The high impact of toe resistance on the reinforcement force poses a design dilemma as to the reliability of this resistance, even if attainable. Practically, the leveling pad is not intended to serve as a critical structural element and thus should not be relied on for maintaining the toe resistance in long-term design. Economically, ignoring the toe resistance has little impact on the overall cost. [ABSTRACT FROM AUTHOR]

The nonlinear response of shallow foundations has been studied experimentally and analytically. However, the engineering community is not yet convinced of the applicability of such concepts in practice. A key prerequisite is the ability to realistically model such effects. Although several sophisticated constitutive models are readily available in the literature, their use in practice is limited, because (1) they typically require extensive soil testing for calibration; (2) as they are implemented in highly specialized numerical codes, they are usually restricted to simple superstructures; and (3) in most cases, they can only be applied by numerical analysis specialists. Attempting to overcome some of these difficulties, this paper develops a simplified but fairly comprehensive constitutive model for analysis of the cyclic response of shallow foundations. On the basis of a kinematic hardening constitutive model with Von Mises failure criterion (readily available in commercial finite element codes), the model is made pressure sensitive and capable of reproducing both the low-strain stiffness and the ultimate resistance of clays and sands. Encoded in ABAQUS through a simple user subroutine, the model is validated against (a) centrifuge tests of shallow footings on clay under cyclic loading and (b) large-scale tests of a square footing on dense and loose sand under cyclic loading, conducted in the European Laboratory for Structural Analysis for the TRISEE project. The performance of the model is shown to be quite satisfactory, and discrepancies between theory and experiment are discussed and potential culprits are identified. Requiring calibration of only two parameters and being easily implemented in commercial FE codes, the model is believed to provide an easily applicable engineering solution. [ABSTRACT FROM AUTHOR]

This paper deals with the dynamic steady-state force-displacement relationships (impedance) for rigid foundations of arbitrary shape resting on a semi-infinite medium consisting of homogeneous, isotropic, linear elastic materials using the boundary element method (BEM). An elaborate numerical technique is used to calculate Green's function, yielding a highly accurate numeric approximation in an explicit form. By using a BEM formulation for triangular elements (linear and infinite shape function) compliance of rigid massless surface foundations was obtained. The use of triangular elements causes stress continuity between elements to be satisfied. Meanwhile, the tendency for foundation edge stresses toward infinity can be modeled by using these triangular infinite stress elements. As a result of this, computations are more accurate but less time-consuming. This procedure is used to evaluate the vertical rocking compliance functions for rigid rectangular, circular, and square foundations with internal holes. Finally, comparisons are made between the results obtained from the proposed approach and those from other methods. [ABSTRACT FROM AUTHOR]

In this paper, we examine the use of boundary springs as approximate external boundary conditions for the typical soil islands encountered in finite-element (FE) models of soil-foundation interaction problems. We present a set of simple uniformly distributed boundary springs and a set of variable boundary springs that account for the lateral distribution of contact forces between the foundation and the soil. We evaluate the accuracy of the approach for shallow foundations resting on soil islands of different dimensions. It is shown that significantly smaller errors can be achieved with these boundary springs than those obtained when fixed-fixed or fixed-free external boundary conditions are used. We present an iterative approach to determine the boundary springs for cases in which extremely small soil islands are required. Although the approach suggested to determine the boundary springs is best suited to shallow foundations, good results are also obtained for pile foundations. The approach presented applies to a uniform elastic half-space, but extensions to layered media are possible. [ABSTRACT FROM AUTHOR]

There is currently a lack of established calculation methods for the geotechnical design of heat exchanger piles, although the technology is experiencing a fast expansion. Instead of quantifying the effects of temperature changes on the static behavior of heat exchanger piles, the common geotechnical practice is to apply a large overall security factor. This is done to be on the side of safety with respect to thermal effects. The few existing in situ experiments show that applying a thermal load induces a significant change in the stress-strain state of a pile. This paper presents a geotechnical numerical analysis method based on the load-transfer approach that assesses the main effects of temperature changes on pile behavior. The method is validated on the basis of in situ measurements of the loads and deformations experienced by heat exchanger test piles. The occurrence of critical design situations is further discussed. Some conclusions are formulated on concrete failure and the full mobilization of the pile shaft friction and base resistance during the operation of the heat exchange system. [ABSTRACT FROM AUTHOR]

Neural network (NN) models for time series forecasting were initially used in economic fields. In this paper, NN models for time series forecasting are introduced for use in forecasting the settlement of chimney foundations. The data sets used in the NN models were measured in the field. Seven models with different input series are developed to determine the optimal structure of the network. In evaluating the network performance, the network model that uses the previous nine months' settlement values as input is selected as the optimal model. The analysis results demonstrate that the settlement values predicted by the optimal model are in good agreement with the field measurements. In addition, as the number of data points in the input series increases, the NN performance clearly improves, and this improvement stops after the input series has increased to a certain extent. This demonstrates that the time-series-based NN model can also be successfully applied to predict foundation settlement. [ABSTRACT FROM AUTHOR]

Pile-soil interaction in an expansive soil foundation has been primarily analyzed by an analytical solution in our previous study. As a complementary work, this paper briefly reviews the derivation process in more detail and extends the capability of the solution in dealing with the pile-soil interaction issue under various conditions. The results show that (1) increasing pile length is able to effectively decrease the upward pile movements, but meanwhile, the tensile stresses along the pile shaft increase as well; (2) a critical pile diameter exists (d≈0.04L); (3) when the diameter is less than this value, the upward pile movements can be reasonably reduced, but for the pile with a larger diameter, it has little effect on reducing the upward pile movements, and as irrigation proceeds, both the displacements and tensile stresses increase and both tend to be much less sensitive to the water's incoming over time; and (4) a critical applied pressure for preventing the upward pile movements that is induced by soil's swelling pressure is found to be 2.5 times of the maximum tensile stress of the free pile only under swelling pressure in expansive soil foundation. [ABSTRACT FROM AUTHOR]

The reinforcement of soft soils by rigid inclusions is a practical and economical technique for wide-span buildings and the foundations of embankments. This method consists of placing a granular layer at the top of the network of piles to reduce vertical load on the supporting soil and vertical settlement of the upper structure. The study focuses on the modeling of load-transfer mechanisms occurring in the reinforced structure located over the network of piles with a coupling between the finite-element method (geosynthetic sheets) and discrete element method (granular layer; concrete slab in some cases). The importance of granular layer thickness to increase load-transfer intensity and to reduce vertical settlement was observed. However, without a basal geosynthetic sheet, the compressibility of soft soil has a great influence on the mechanisms. A method predicting the intensity of load transfers was proposed, based on Carlsson's solution. The main parameters concerned are the geometry of the work and the peak and residual friction angles of the granular layer. [ABSTRACT FROM AUTHOR]

In this paper, we study the deformation and stability of a pinned buckled beam under a point force. The buckled beam is constrained by a tensionless elastic foundation, which is flat before deformation. From static analysis, we found a total of five different deformation patterns: (1) noncontact, (2) full contact, (3) one-sided contact, (4) isolated contact in the middle, and (5) two-sided contact. For a specified set of parameters, there may coexist multiple equilibria. To predict the response of the buckled beam foundation system as the point force moves from one end to the other, we have to determine the stability of these equilibrium configurations. To achieve this, a vibration method is adopted to calculate the natural frequencies of the system, taking into account the slight variation of the contact range between the buckled beam and the tensionless foundation during vibration. It is concluded that among all five deformation patterns, Deformations 1, 2, 3, and 4 may become stable for certain loading parameters. In the extreme case in which the foundation is rigid, on the other hand, only Deformations 1 and 3 are stable. [ABSTRACT FROM AUTHOR]

A geotextile-reinforced embankment was built over soft ground. Staged construction and vertical prefabricated drains were used to obtain strength gain via consolidation of the foundation material. Settlement and pore pressure were measured as a part of construction control. Settlement, differential settlement, and rate of consolidation were predicted by simple models. Uncertainties in the predictions were evaluated to assess the reliability of the predictions. The estimated errors were compared with the measured values, and major contributors to prediction errors were identified. [ABSTRACT FROM AUTHOR]

This paper will focus on the legal liability issues facing the professional engineer engaged in the design and construction administration of facilities built on expansive soils. These legal liability issues will be discussed from the perspectives of the geotechnical, civil, and structural engineer to alert those professionals to the legal ramifications of their daily activities. By focusing on these legal aspects facing the engineers that are involved in the process of building on expansive soils, hopefully litigation can be avoided or successfully defended. Attention to the legal ramifications of engineering is mandated by today's litigious environment in the construction industry, especially when designing and administering the construction of facilities built on expansive soils. [ABSTRACT FROM AUTHOR]

Construction on expansive soils is challenging and thus prone to some problems and litigation. The engineering community makes extensive use of local experience and empirical procedures to address these problems. Although there has been extensive study of expansive soils and foundations on expansive soils, data related to performance of residential structures are limited in general and limited in the Phoenix area, in particular. In this study, an overview of the Phoenix Valley, Arizona, geotechnical practice and foundation performance related to residential structures on expansive clays, was developed through surveys and interviews with geotechnical engineers, structural engineers, and homebuilders. Using data obtained from files of Phoenix area geotechnical firms and government agencies, the existing Natural Resource Conservation Service map showing expansive soil locations throughout the Phoenix region was updated through the use of correlation developed in this study relating expansion index to common soil index properties such as Atterberg limits and percent passing the No. 200 sieve. Files of forensic investigations linked to expansive soil regions were made available for this study by several geotechnical engineering firms, and Phoenix Valley areas where forensic investigations have been identified, were mapped for comparison to regions identified in the updated map as having expansive soils. Comparison of the forensic investigation map to the updated map of expansive clay locations revealed that most of the forensic investigations were in regions identified with clays labeled as high to moderately high expansion potential, with a few forensic investigations in regions of medium expansion potential. Finally, unsaturated flow analyses were conducted for an Arizona expansive clay profile for two very different landscaped conditions of well-irrigated turf and desert landscape. The results of the numerical analyses were consistent with the reported observations and modes of failure identified through the surveys and interviews conducted with engineering and homebuilder professionals, including the finding that site drainage was found to be extremely important to good foundation performance, regardless of the type of landscape selected. [ABSTRACT FROM AUTHOR]

Field measurements of foundation movements in central Mississippi have revealed design issues involving expansive soils. At one building, field measurements of the first floor slab at 14 locations show that heaving occurred at a steady rate during part of an extensive drought. The steady rate was maintained throughout the final 21.5 months of a 23.5-month study period following a record drought that occurred at the beginning of the study. The average change in the movement rate was 2.9 mm (0.11 in.) per year over the last 21.5 months. Median movement rates for all the pins varied from 25 mm (0.98 in.) per year to 1.8 mm (0.07 in.) per year excluding the measurements made during the first part of the drought. Elevation surveys at another facility show how the rate of heave is influenced by geologic variations. These surveys also show how the depth of clay (from the surface) influenced heave and how differential movements of a structure are produced from these variations in geology. Design procedures for kind of movement are discussed. [ABSTRACT FROM AUTHOR]

Construction of buildings using a slab on grade and belled drilled piers to support column loads in central Mississippi has performed poorly. Similar buildings where the first floor was poured on 15.2 cm (6 in.) cardboard box forms have not fared much better. The first floor of this building was a slab on grade that was dowelled to a grid of grade beams. The grade beams were dowelled to drilled piers. The top of the expansive Yazoo clay varied from 1.8 to 3.66 m (5.9-12 ft) deep. High swell pressures developed under the slab and began to lift the building. A frame analysis showed that foundation movements were significantly changing the stresses of the structural steel frame. About half of the drilled piers of the building were found to be damaged near the connection with the grade beam. Two piers had separations of 10.2 and 8.9 cm (4 and 3.5 in.). During the foundation repair, the building frame was releveled and eight damaged piers were replaced. Recommendations to reduce the risk of this kind of damage were made. [ABSTRACT FROM AUTHOR]

This paper examines the background, history, and results of multiple investigations associated with pyrite-based expansive soils spanning almost 40 years in conjunction with a private elementary school located in western Pennsylvania. The school was initially designed in 1960. Original construction was completed in September 1961 and the first signs of distress, which were primarily related to slab heave, were reported in early 1962. One wing of the school, a 1965 classroom addition (1965 addition) with different structural and foundation systems, did not experience any expansive soil-related damages and served as a valuable comparison throughout multiple subsequent investigations. Pyritic soil material in the subgrade in conjunction with oxygen-rich groundwater was determined to be the cause of soil movement and building distress. Expansive soil-related problems at the school continued for decades despite an investigation, civil court action, and judgment in the late 1960s followed by a remediation program in the 1970s and 1980s. Following a second round of investigations and litigation in the late 1990s, all of the original classroom, office, and gymnasium building sections, with the exception of the 1965 addition, were demolished in late 2000 and early 2001 based on safety concerns and economic evaluation. Investigation and monitoring to confirm subgrade conditions continued throughout the demolition process. As a part of this paper, the history of this case dating back to one of the early identifications of pyrite as an expansive element of concern in building construction, including one of the earliest comprehensive identifications of the complete chemical-microbiological oxidation process is presented. The initial 1960s investigation and conclusions are identified as well as the series of engineering, procedural, and construction errors that took place during and after the first remediation process that led to ongoing soil expansion and structural damage, including misguided actions and misunderstandings that complicated and delayed a final resolution in this case. Today, the industry is more familiar with the potential for pyrite-related construction problems, nevertheless, the paper incorporates lessons learned for avoiding problems and in particular, the procedural failures that led to the eventual need to abandon and demolish the school facility. [ABSTRACT FROM AUTHOR]

This note utilizes the analog models of forced vibration to express the mass of foundation block in terms of damping ratio and thereafter obtains the expression for the minimum foundation mass required to limit vertical machine vibration amplitude to a prescribed limit. The resulting formula, which accounts for internal damping, is constrained by the limitations of the original analog solutions. Moreover, formulas are derived for determining the damping ratio for conditions different from optimum that enable the evaluation of the nonoptimum foundation mass required to limit vibration. Since the ideal optimum solution may not be practical, an expression has been derived for the best nonoptimum foundation mass. The method presented in this note is believed to be easier to implement and to yield smaller foundation blocks than the existing traditional method, and thus will enable cheaper machine foundations to be constructed. It is believed that the proposed optimal solution may lead to the near elimination of machine vibration nuisance produced by high-frequency machines during operation. [ABSTRACT FROM AUTHOR]

The behavior of pile foundations subjected to horizontal loading is typically evaluated using horizontal load tests. Although load tests are valuable to understand site-specific soil-structure interaction phenomena, validated predictive methods are also useful during the design phase. In this study, the results from horizontal load tests are compared with methods which predict the horizontal bearing capacity of piles using in situ measurements of soil behavior. Specifically, several horizontal load tests were performed in order to evaluate the behavior of two 12-m long Strauss piles and four bored piles with similar length, all installed in a lateritic soil profile. Two prediction methods were evaluated using p-y curves computed from the results of Marchetti's dilatometer test (DMT) results. The predictive methods using the p-y curves from the DMT showed good agreement with the behavior observed in the pile loading test. [ABSTRACT FROM AUTHOR]

Effective (design) thermal resistivity values for use of rigid, cellular polystyrene foam insulation in below-ground frost-protection applications play an important role in the success of the ASCE 32-01 standard. The ASCE 32-01 standard is currently recognized in U.S. model building codes as a cost-effective means of protecting building foundations against frost heave in regions with seasonal ground freezing and no permafrost. The long-term thermal performance of foundation insulation used for this purpose is, therefore, a critical building performance concern. This same concern also has relevance to sustained performance of below-ground insulation used for energy conservation purposes. This paper provides a critical review and analysis of data reported in the literature on below-ground thermal performance of rigid, cellular polystyrene foam insulations. These products can be molded expanded polystyrene or extruded polystyrene as defined by ASTM C578 in ASTM 2008 Standard. The findings serve to document and confirm effective thermal resistivity values originally incorporated into the ASCE 32-01 standard for frost protection of building foundations. [ABSTRACT FROM AUTHOR]

Local scour around complex piers under steady clear-water condition was studied experimentally for a variety of configuration, including different sizes and shapes of complex piers. A total of 70 experiments were carried out. Three sets of experiments were performed over the entire range of possible pile cap elevations for complex piers with different geometrical characteristics. The collected data are used to quantify the pile cap elevations that maximize or minimize the local scour depth. Some of the available methodologies to estimate the maximum local scour depth around such complex piers are evaluated. The predictions of the scour depths improved by using the revised methods of Hydraulic Engineering Circular Number 18 and Coleman. [ABSTRACT FROM AUTHOR]

Full-scale testing can be an integral component of quality control/quality assurance for projects involving construction of deep foundations. Rapid load tests are being used in the deep foundation industry as a method for assessing the axial static behavior of deep foundations. Since rapid load tests involve dynamics, inertial and damping forces must be considered in analyzing measured pile response to estimate the static pile response. The unloading point method (UPM) is typically used for this purpose. Generally considered a consequence of load rate effects in clays, results from the UPM must be further modified by a reduction factor to obtain a reasonable estimate of the static pile response. A reduction factor of 0.65 applied to the UPM for clay soil sites has been recommended by others. However, a review and analysis of readily available literature reporting static and rapid pile load test results at sites predominantly consisting of clay soils indicate that an average reduction factor of 0.47 is more appropriate. Rapid load testing should be used judiciously. When using the UPM to estimate static pile capacity from rapid load tests in clay, static load tests should be performed to validate the reduction factor used to interpret rapid load tests. [ABSTRACT FROM AUTHOR]

This paper presents a sensitivity-based damage identification of a three-dimensional truss tower tested in the laboratory. A finite-element model is updated by modal parameters obtained from ambient vibration measurements. The paper focuses on details of modeling and model updating. To get a realistic model, it was necessary to include eccentric connections, bending stiffness in truss members, and foundation flexibility. For model updating, a number of mathematical techniques are combined in a consistent way, including regularization of the nonlinear updating problem and its linearization. Considering all these details correctly, damage in the truss has been successfully identified. However, it is also demonstrated how neglecting some of these algorithmic details can lead to incorrect results. It is also shown how static condensation can lead to a model that is valid for the undamaged case but cannot adequately represent the damaged case. [ABSTRACT FROM AUTHOR]

Analyzing and designing a crane supporting system can be time-consuming process. In particular, the dynamic nature of mobile crane operations entails a variety of reaction values for truck and crawler cranes. The platform of a mobile crane can either be set on outriggers—denoted as a truck crane, or on a crawler tracks—denoted as a crawler crane. Designing of a mobile crane supporting system depends on the lifting configuration, type of crane and the type of materials to be used under the crane outriggers or crawler tracks. This paper presents an automated system which is designed to assist practitioners in calculating the mobile crane’s support reactions and in designing the supporting system. This system is developed such that it can generate a 2D reaction influence chart which shows the reactions for each outrigger at varying horizontal swing angles and vertical boom angles to the ground. Most of the geometric configurations needed to perform the support design are not ordinarily given in crane manufacturer’s manual and to address this deficiency, this newly developed system has been integrated with a previously developed crane database which contains information on widely used mobile cranes for construction along with a crane selection system. A case example is described in order to demonstrate the use and effectiveness of the presented system in automating crane lift analysis. [ABSTRACT FROM AUTHOR]

Pile groups are frequently designed with equal or similar pile lengths. However, the significant interaction effects among equal-length piles imply that this may not be the optimized configuration. This paper presents the optimization analyses of piled rafts and freestanding pile groups, where pile lengths are varied across the group to optimize the overall foundation performance. The results of the analyses are applicable in cases where the piles derive a majority of the capacity from the frictional resistance. It is demonstrated that, with the same amount of total pile material, an optimized pile length configuration can both increase the overall stiffness of the foundation and reduce the differential settlements that may cause distortion and cracking of the superstructure. The benefits of the optimization can be translated to economic and environmental savings as less material is required to attain the required level of foundation performances. The reliability of the optimization benefits in relation to construction-induced variability is also discussed. [ABSTRACT FROM AUTHOR]

The effect of foundation embedment on consolidation has not been considered previously in a systematic manner, although this is of particular interest for offshore foundations, where embedment is provided by skirts that enclose a compressible soil plug. For skirted foundations, critical uncertainties include what to assume in terms of the degree of drainage at skirt tip level, and the relative time scales of consolidation within the soil plug and beneath the foundation. In this paper, results from small strain finite-element analyses are used to quantify the immediate and time-dependent response of circular skirted foundations to uniaxial vertical loading. Foundations with frictionless and fully rough skirt-soil interfaces with varying ratio of embedment depth to foundation diameter are considered and the responses compared with those for surface foundations. The findings show that both skirt-soil interface roughness and embedment ratio have a significant effect on the consolidation response. [ABSTRACT FROM AUTHOR]

A matrix formulation to determine the coupled response of rigid foundations where soil properties are modeled by springs and dashpots is presented. Location and orientation of springs and dashpots can be arbitrary, thus a general solution is determined. The response is given in terms of translational and rotational displacements considering coupled effects. Physics of the problem presented here has been extensively studied and a broad range of useful formulae to determine springs and dashpots properties for soil-structure interaction is available. These published formulae for springs and dashpots properties are an input to the approach presented. Thus, the novelty of this approach is a matrix manipulation that leads to a simple expression allowing coupling all degrees of freedom even when springs and dashpots are not orthogonally oriented. For validation purposes, finite element solutions are compared with the approach presented. [ABSTRACT FROM AUTHOR]

This paper presents an analytical solution for the consolidation of soft soil foundations reinforced by stone columns under time-dependent loadings. The differential equations of the foundations reinforced by stone columns are obtained including smear and well resistance under arbitrary applied loadings. The closed-form solutions of pore pressure and the overall average degree of consolidations are obtained for some common types of loadings, such as step loading, ramp loading, and cyclic trapezoidal loading. By solving the equations using a semianalytical method, the comparisons agree very well with the existing analytical solutions, which verify the correctness and accuracy of the proposed methods. Using the solutions obtained, some selected charts are presented and the relevant consolidation behavior is investigated and discussed. [ABSTRACT FROM AUTHOR]

A foundation system may involve more than a single footing with an arrangement such that the footings are sufficiently closely spaced that adjacent footings interact. Vertical, horizontal, and moment capacity of multifooting foundation systems are potentially dependent on footing interaction, and in particular overturning capacity can be significantly enhanced by the structural rigidity of a multifooting foundation system. There is no established procedure for the calculation of bearing capacity of a shallow foundation system comprising cojoined footings and ad hoc approaches may simply involve summing the ultimate limit states of the individual footings as if they acted independently; neglecting additional capacity of the system available from the kinematic constraint provided by the structural connection between the footings. Plane strain finite-element analyses have been carried out to investigate the undrained ultimate limit states under general loading of skirted two-footing foundation systems at various normalized spacing compared to a single skirted footing of equal bearing area and embedment ratio. [ABSTRACT FROM AUTHOR]

The capacity of a pile-soil system can be obtained by pushover analysis using the beam-on-nonlinear-Winkler foundation model. When the pile section enters the plastic state, the plastic hinge method is usually adopted to model its postyielding flexural behavior. The propagation of the plastic zone in a pile can be traced using a series of plastic hinges distributed along the pile that is embedded in the soil. This study proposes a proper model for arranging the distributed plastic hinges along the depths of the pile that are prone to yielding. A modified definition of plastic curvature is proposed herein in order to correctly simulate the nonlinear flexural behavior of a pile. Examples are presented to show the effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

Tapered piles in comparison to cylindrical piles can be beneficial in terms of the load capacity. In this paper, estimation of the load capacity for tapered piles using cone penetration test (CPT) resistance was investigated. Fourteen calibration chamber load tests using different pile types and six CPTs were conducted under various soil conditions. From the calibration chamber test results, the total, base, and shaft load capacities were analyzed in terms of soil conditions and taper angle. To evaluate CPT-based load capacity of tapered piles, normalized base and shaft resistances were obtained from normalized unit load-settlement curves. Based on the normalized base and shaft resistances, design equations that can be used to evaluate the base and shaft resistances of tapered piles were proposed. The proposed method is valid for sands of medium to dense conditions, while it may result in unconservative predictions for loose sands. To check the accuracy of the proposed method, field load tests using both cylindrical and tapered piles were conducted and compared with the predictions using the proposed method. A simplified approach using an equivalent cylindrical pile was also investigated and compared. [ABSTRACT FROM AUTHOR]

Underground tunnels are considered to be a vital infrastructure component in most cities around the world. Careful planning is always necessary to ensure minimum impact on nearby surface and subsurface structures. This study describes the experimental investigation carried out to examine the effect of existing piles installed in cohesive soil and extended to bedrock on the circumferential stresses developing in a newly constructed tunnel supported by a flexible lining system. A small scale testing facility was designed and built to simulate the process of tunnel excavation and lining installation in the close vicinity of preinstalled model piles. Lining stresses were measured for different separation distances between the lining and the existing piles Consistent decrease in the lining load was observed when the piles are located within a distance of one tunnel diameter from the tunnel. The results presented in this study indicated that measuring the lining response near existing pile foundations may be used to evaluate the extent of the interaction between the lining and the surrounding piles. [ABSTRACT FROM AUTHOR]

The existence of large magnitude stresses at the tip of a bearing pile is a well known phenomenon leading to crushing of soil grains and thus affecting pile behavior. Classical foundation design calculations which assume that the soil fails in shear and neglect volume change can be safely used where stress levels or particle strengths prevent crushing, however in the case of weak grains or high foundation stresses consideration should be given to the effects of grain crushing and the resulting volumetric compression. Model pile tests have been carried out in two skeletal carbonate sands and a standard silica sand with the aim of examining the variation of skin friction and end bearing capacities with degree of penetration. The mobilization of the strength of crushable soils requires a much higher strain level while at the same time the end bearing pressure on the model piles exceeded 10 MPa inducing considerable particle breakage. The peak skin friction for all sands occurred at a settlement normalized by pile diameter, S/D, of less than 0.1. At this point the carbonate sands generally had lower skin friction values than the silica sand. Further displacement caused a rapid decrease in skin friction for all three materials. At higher lateral stresses the less crushable Toyoura silica sand generated higher skin frictions. Samples of Chiibishi sand were sectioned and photographed. It was observed that a spherical plastic zone was formed at the base of the pile which expanded with increasing S/D and a degraded layer of broken particles developed around the pile as S/D increased. Large values of the Marsal particle breakage factor were restricted to a zone extending outwards to one pile radius. An end bearing capacity modification factor has been proposed to adapt the conventional bearing capacity equation for soil crushability. This modification factor is a function of soil compressibility and degree of penetration. The factor was shown to decrease with increasing soil compressibility and increase with normalized penetration S/D. [ABSTRACT FROM AUTHOR]

There is generally a physical limit to the smallest possible capacity for a deep foundation. However, a lower bound on the capacity has rarely been accounted for in performing reliability analyses and developing reliability-based design codes. The objectives of this paper are to investigate the effect of having a lower-bound capacity on the reliability of a geotechnical engineering system and to propose a load and resistance factor design (LRFD) checking format that includes information on the lower-bound capacity in design. It is concluded that a lower-bound capacity can cause a significant increase in the calculated reliability for a geotechnical design even if it is an uncertain estimate. Two alternative LRFD formats that incorporate lower-bound capacities and that would not require substantive changes to existing codes are proposed. Real-world examples dealing with the design of onshore and offshore foundations indicate that the incorporation of a lower-bound capacity into design is expected to provide a more realistic quantification of reliability for decision-making purposes and therefore a more rational and efficient basis for design. [ABSTRACT FROM AUTHOR]

This note presents a method for predicting nonlinear response of pile groups in clays, subjected to vertical loads. The method is based on mobilizable strength design (MSD) concepts, in which the mobilized strength is associated with the shear strains developed in the soil. The suggested procedure is incremental, and requires evaluation of a displacement field. A simple procedure of superposition of pattern functions is suggested for the construction of a complete displacement field. The incremental procedure allows for the variation of the displacement field throughout the loading process, according to principles of minimum energy and compatibility requirements among the piles. Essentially, the procedure allows consideration of a nonlinear continuum between the piles. The pattern functions are an adaptive form of the logarithmic function suggested by Randolph and Wroth in 1979. Under small load levels, when the soil is essentially elastic, the procedure yields values comparable to those from the elastic solution of Randolph and Wroth. At larger strain levels, nonlinear pile group response is simulated based on the soil constitutive models specified by the practitioner. The method is applicable to cases where shaft loading does not induce volume changes in the soil. The method is compared with three dimensional finite difference simulation of undrained loading of pile groups with a nonlinear soil constitutive model. Fair agreement is observed. [ABSTRACT FROM AUTHOR]

This technical note develops a design approach that integrates economic design optimization with reliability-based methodologies to rationally account for geotechnical-related uncertainties. The geotechnical related uncertainties are addressed using a reliability-based approach in the assessment of ultimate limit state (ULS) and serviceability limit state (SLS) requirements. This design approach is illustrated using an example of spread foundation under drained uplift loading. Comparison of the economically optimized design with conventional designs shows that cost of the economically optimized design is lower than that of other feasible designs, and increasing foundation depth is a relatively effective way to increase uplift capacity. Impacts of geotechnical property uncertainties on foundation construction costs are quantified, and the results form a basis of a quantitative cost-benefit analysis of reducing geotechnical property uncertainties. Operative horizontal stress coefficient (K) is shown to be the key parameter that significantly affects the design of a spread foundation under drained uplift, and therefore, deserves attention in site investigation. For a typical allowable uplift displacement ya=25 mm, the spread foundation design is dictated by the ULS requirement, and the effect of ya, or SLS requirement, is negligible. [ABSTRACT FROM AUTHOR]

A series of centrifuge model tests is reported that investigated the effects of foundation position on the interaction of reverse, dip-slip faults with shallow foundations resting on sand. The model tests have allowed careful examination of both the soil and foundation deformation as a shear localization (fault) propagates through a 15 m thick sand layer for fault throws up to 5 m. By comparing results of the tests with foundations present with those from a “free-field” test, the effect of the foundation on the faulting pattern has been observed directly. The response of the foundation is very sensitive to the exact position of the fault and even when the fault emerged remotely from the foundation it sometimes caused significant foundation movements. Detailed results are presented for the tests and it is suggested that these results are used as: (1) indications of likely foundation–soil–fault interaction mechanisms; and (2) to allow future validation of numerical models for similar problems. Finally, foundation rotations measured during the fault–foundation interaction tests are compared to those predicted using a simple method based on free-field soil displacements. This simple method makes surprisingly good prediction of maximum fault rotations for different throws. [ABSTRACT FROM AUTHOR]

This paper is concerned with the vertical vibration of a flexible foundation resting on a saturated layered soil half-space that consists of a dry soil layer and an underlying semi-infinite saturated soil. The problem is of the mixed boundary value type and, by means of the Hankel transform technique, the determination of dynamic compliance coefficient and contact stress distribution leads to a pair of dual integral equations. These equations are then reduced to a Fredholm integral equation of the second kind, which is solved by standard numerical procedure. Some limiting cases existing in the literature are revisited to validate the accuracy of the present solution. Extensive numerical results are presented to illustrate the influences of the thickness of the overlying dry soil, the foundation flexibility, and the shear modulus ratio between dry and underlying saturated soils on the dynamic responses of the flexible foundations. [ABSTRACT FROM AUTHOR]

Most of the existing mechanical models for shear strength and strain calculation of beam–column joints do not explicitly account for bond conditions of the longitudinal reinforcement of the connected members that are anchored inside the joint region. When considered, bond is accounted for through empirical parameters. In this paper, an analytical method for the definition of the strain distribution along the anchorage of the column longitudinal reinforcement inside a bridge monolithic connection is proposed. The anchorage capacity of the main column reinforcement is considered to be affected by two independent mechanisms. The capacity of the first mechanism depends on the average bond stress along the elastic part of the anchorage that is calculated by a mathematical solution without taking into account the beneficial effect of the transverse reinforcement. The capacity of the second mechanism depends on the coefficient of friction arising between main column bars and transverse reinforcement that encloses and restrains the anchorage. The coefficient of friction is empirically set in relation to the position of the transverse bar; either along the elastic part of the anchorage or in the part where yielding penetrates inside the joint. A parametric evaluation of the main design parameters affecting the anchorage capacity is conducted next. The proposed model is finally used in calculating the joint shear response of selected bridge connection specimens for which reported data of strain distribution along anchorages exist. The calculated values correlate successfully with the associated experimental data. [ABSTRACT FROM AUTHOR]

Depending on the relevant material properties, failure of grouted anchor anchorage to concrete can result from pullout of concrete cones, debonding at either anchor-grout or grout-concrete interface, fracture of anchor, and combination of some of these failure modes. The intention of the present study is to present an analytical method for analyzing the concrete cone failure during the process of interfacial debonding by using deformation compatibility conditions at the anchor-grout and grout-concrete interfaces. The tensile stress in the anchor and interfacial stresses at the two interfaces are formulated at different loading stages. It is assumed that interfacial debonding modeled as an interfacial shear crack only appears at the anchor-grout interface and is initiated from the loaded end. The concrete cone and interfacial debonding failures are analyzed according to the sizes and material properties of the anchorage. Three different failure modes are considered, including concrete cone failure at the unloaded end without interfacial debonding, interfacial debonding plus concrete cone failure at the same height as the interfacial shear crack tip, and interfacial debonding plus concrete cone failure at the unloaded end. In each case, the load for the initiation of the concrete cone failure, and the cone angle are determined analytically. Subsequently, material and structural parameters are adopted to study their influences on the failure modes and calculated results. It is found that if the embedment length is relatively long, the concrete cone failure occurs within a local scope. If the concrete diameter is large enough, the failure mode is the interfacial debonding without concrete cone failure. The conclusions provide useful references for engineering practice such as designing grouted anchor anchorage to concrete in light of different needs and failure modes. [ABSTRACT FROM AUTHOR]

Observations after earthquakes where surface fault ruptures crossed engineering facilities reveal that some structures survived the rupture almost unscathed. In some cases, the rupture path appears to divert, “avoiding” the structure. Such observations point to an interaction between the propagating rupture, the soil, and the foundation. This paper (i) develops a two-step nonlinear finite-element methodology to study rupture propagation and its interaction with strip foundations; (ii) provides validation through successful Class “A” predictions of centrifuge model tests; and (iii) conducts a parameter study on the interaction of strip foundations with normal fault ruptures. It is shown that a heavily loaded foundation can substantially divert the rupture path, which may avoid outcropping underneath the foundation. The latter undergoes rigid body rotation, often detaching from the soil. Its distress arises mainly from the ensuing loss of support that takes place either at the edges or around its center. The average pressure q on the foundation largely dictates the width of such unsupported spans. Increasing q decreases the unsupported width, reducing foundation distress. The role of q is dual: (1) it compresses the soil, “flattening” fault-induced surface “anomalies”; and (2) it changes the stress field underneath the foundation, facilitating rupture diversion. However, even if the rupture is diverted, the foundation may undergo significant stressing, depending on its position relative to the fault outcrop. [ABSTRACT FROM AUTHOR]

It has been recognized that the ductility demands on a superstructure might be reduced by allowing rocking behavior and mobilization of the ultimate capacity of shallow foundations during seismic loading. However, the absence of practical reliable foundation modeling techniques to accurately design foundations with the desired capacity and energy dissipation characteristics and concerns about permanent deformations have hindered the use of nonlinear soil–foundation–structure interaction as a designed mechanism for improving performance of structural systems. This paper presents a new “contact interface model” that has been developed to provide nonlinear relations between cyclic loads and displacements of the footing–soil system during combined cyclic loading (vertical, shear, and moment). The rigid footing and the soil beneath the footing in the zone of influence, considered as a macroelement, are modeled by keeping track of the geometry of the soil surface beneath the footing, along with the kinematics of the footing–soil system, interaction diagrams in vertical, shear, and moment space, and the introduction of a parameter, critical contact area ratio (A/Ac); the ratio of footing area (A) to the footing contact area required to support vertical and shear loads (Ac). Several contact interface model simulations were carried out and the model simulations are compared with centrifuge model test results. Using only six user-defined model input parameters, the contact interface model is capable of capturing the essential features (load capacities, stiffness degradation, energy dissipation, and deformations) of shallow foundations subjected to combined cyclic loading. [ABSTRACT FROM AUTHOR]

Results are presented from laboratory experiments to investigate the effectiveness of bed sills as countermeasures against local scouring at a smooth circular bridge pier, for flow conditions near the threshold of uniform sediment motion. The bed sill was located downstream of the pier, and its effectiveness with the distance between pier and sill was evaluated. The dependence of the scour depth on different dimensionless groups was defined. The results showed that a bed sill placed at a short distance downstream of the pier reduces the scour depth, area, and volume. In particular, the smaller the distance between the two structures, the larger the effectiveness of the countermeasure. The bed sill seems to take effect some time after the beginning of the test, as the scour hole downstream of the bridge pier develops sufficiently and interacts with the countermeasure. [ABSTRACT FROM AUTHOR]