Advances in Soil Dynamics and Foundation Engineering

Track vibration of a tramway in operation was theoretically analyzed. The relationships of critical velocity with elastic modulus of subgrade and thickness of track beds were obtained by solving vibration equation. It was shown that the critical velocity was greater than the design speed of trams. Another vibration differential equation was established to analyze track vibration. Both equations adopted moving impact load and ignored the impact of damping, but irregularities of rails were considered in the second equation. The analytical solutions of vibration deflection and acceleration were deduced. Based on the solutions and superposition principle, the dynamic responses under single axle loading and tram loading were analyzed. The results indicate that: (1) vibration deflection increases exponentially with irregularities amplitude; and (2) vibration acceleration has a negative logarithmic correlation with irregularity amplitude.

The opening of the Qinghai-Tibet Railway, which runs across the permafrost region on the Qinghai-Tibet Plateau, leads to an increasing concern for the stability of the embankment. The maintenance of the railway and assessment for its influence to the permafrost require an effective investigation method. The authors carried out a field test and studied the applicability of High Density Surface Wave Survey (HDSWS) for the investigation. The field test was carried out on the natural ground and the railway embankments with various soil structures. For data processing, first, the phase velocities of Rayleigh wave were estimated from the recorded seismic data. Then, the shear wave velocity (Vs) profiles were calculated by multi-mode phase velocity inversion. The results revealed the Vs structure of the embankment as well as the natural ground. Being coincident with soil structure of the embankment and borehole data on the natural ground, the test result shows that the HDSWS is effective for permafrost investigation.

The defects in high-speed railway embankment will grow during operation. It will bring potential risk to railway safety. In order to develop an efficient detection method for the defects in embankment, a numerical simulation and field model test are carried out to study the influence of defect on wave propagation in embankment. A three-dimensional model of embankment and finite element method is employed, and the characteristics of wave form, amplitude response, and particle motion of sampling point on the slab are taken into account. The field entity model is a full scale one. It was built with materials in accord with the real railway embankment, and the construction methods were all the same. An elastic wave is excited by impacting on the surface of the entity model slab using a rubber hammer. The wave field is observed by vertical geophones on the slab. Common offset gather and common source gather are recorded for seismic imaging and elastic wave analysis. The result of the simulation agrees well qualitatively with that of the field test. It shows that the seismic imaging technique is effective for detecting embankment defects immediately under the slab.

The problem of torsion of a non-homogeneous saturated half-space subjected to certain distribution of dynamic shearing force on the plane boundary is investigated. On the basis of Biot's theory of the saturated soil, the dynamic differential equations of nonhomogeneous saturated soil are established. By using the technique of Hankel transform, the differential equations are solved and the tangential displacement and shear stresses in Hankel transform domain are formulated. Considering the wave radiation condition and the boundary condition at the surface of the saturated half-space, the undetermined coefficients of the displacement and stress in the Hankel transform domain are solved. Then, the displacement field and stress field in the nonhomogeneous saturated half-space are formulated by inverse Hankel transform. Numerical examples are presented to investigate the influence of the nonhomogeneous coefficient and excitation frequency on the torsional dynamic response.

The loess is very sensitive to moisture content. The dynamic and static mechanical properties of loess subgrade under moisture content are important parameters in the design of subgrade. A series of tests - static triaxial, dynamic triaxial, seismic subsidence, and collapse - were carried out under different moisture contents from Shanxi loess. We analyzed the relationships between: (1)the moisture content and the dynamic and static strength, (2) the collapse settlement, and (3) the rebound modulus. The results indicated that the dynamic and static strength decreased with increase of the moisture content. The dynamic strength of the loess is lower than the static strength when the moisture content is less than 15 percent, but the dynamic strength approached or exceeded the static strength when the moisture content was more than 15 percent. The collapse settlement of the loess decreased with the increase of the moisture content, and the seismic subsidence increased with increase of the moisture content. The rebound modulus of the loess decreased with increase of the moisture content. It decreased more with increase of the moisture content when less content of clay and decreased less with increase of the moisture content when higher content of clay. Through test dates analysis, it set up the relationship between dynamic strength and static strength of Shanxi loess.

An experimental study was conducted on ground vibration of the Xiajiao Depot on the Guangzhou Metro Line 3, induced by reverse cyclic loading of metro vehicles on the test line. The regulation of vibration attenuation was analyzed. The results show that the frequency of the vibration waves is mainly in the range of 10 Hz to 80 Hz and the vertical vibration is stronger than the horizontal vibration. The acceleration amplitude of ground vibration is determined by the horizontal distance from measuring points to the track center, and there exists a vibration amplifying zone a certain distance to the track. With the increase of distance, the vibration attenuation of high frequency is faster than that of the low frequency. It is most noteworthy for the vibration attenuation within 6 m to the track center. There is little impact of vibration 38 m from the track, where theaverage of maximum vibration levels of the 1/3 octave is 60 dB. The research on vibration in metro depot is still in the initial stage and it is necessary to carry out special evaluation.

A field measurement was carried out at switch area of Xiajiao Depot of Guangzhou Metro Line 3 to study train-induced ground vibration. The propagation law of ground vibration was investigated in the time-domain and frequency. It was found that the vibration values in two directions attenuate with the distance from the centerline of track, and there are tiny amplified zones at 17 m in the vertical vibration and 23 m in the horizontal vibration. Both the vertical vibration and horizontal vibration should be simultaneously taken into account in the environmental evaluation of the switch area of the metro depot. The frequency corresponding to the peak values of vibration decrease with distance from the centerline of the track and appear at 38-50Hz. In the measuring range of this test, the main frequency range of horizontal vibration is wider than vertical vibration. Compared to other straight rail (no rail switch) test results, the result of this test has broader frequency range.

Sea ports play an important role inthegrowth of any country's economy. To reduce devastation due to seismicity, suitable site specific seismic hazard analysis of ports is a must. In the present paper, site-specific seismic hazard analysis of two important ports - namely, Mumbai port and Jawaharlal Nehru port - which helped Mumbai to beome the financial capital of India, has been evaluated probabilistically. This study develops site-specific seismic hazard curves and uniform hazard response spectra for three different probabilities of exceedance (50%, 10%, and 2%) in a span of 50 years. The epistemic uncertainty in hazard estimation was accounted for by employing seven different ground motion prediction equations developed for worldwide, shallow, crustal, intra-plate environments. The generated response spectrum was compared with that specified by Indian seismic code (IS:1893-Part 1, 2002) for rock sites. Seismic hazard results were deaggregated for three different probabilities to understand the relative contributions of earthquake sources in terms of magnitude and distance. For both ports, the hazard is observed to be at equal distance with different magnitudes for all levels of probability. Also, the larger earthquakes were observed to contribute more significantly to seismic hazard for longer periods for the two ports in the Mumbai metropolitan region.

The installation of bender elements (BE) in different geotechnical testing devices has been increasing in recent years. One of the most widespread combinations in this matter is the use of BE in resonant-column (RC) equipment. Taking into account that the piezoceramic elements can work alternatively as a transmitter or as a receiver, a complementary testing procedure is proposed by using the same RC-BE device. In this case, the perturbation signal is produced by the RC oscillator, while the response of the system is measured by the pair of BE located at each end of the specimen. The analysis of the received data by use of frequency domain techniques allows the dynamic properties of the soil specimen to be obtained. An RC apparatus capable of producing and transmitting a signal with a specific frequency band (i.e. sine sweep or random noise) was equipped with BE and software designed to perform this type of combined tests (TRFD). A laboratory test programme of RC and TRFD combined tests was conducted in order to study the feasibility of this hybrid method. Results indicate that the method could be useful as a complementary tool to evaluate the small-strain stiffness of soil when performing RC and BE tests.

There have been several statistical methods developed to evaluate the probability of seismically induced soil liquefaction. Among these methods, the logistic regression has been the most widely used method to model the probability of liquefaction using the Standard Penetration Test (SPT)- and Cone Penetration Test (CPT)-based case histories. However, the predicted probabilities using logistic regression can be different based on the uncertainties related to distribution of explanatory variables, significance of coefficient of explanatory variables, and distribution of liquefaction to non-liquefaction case histories. In this paper, a possible approach has been developed to select the logistic regression model that best addresses these uncertainties for SPT- and CPT-based case histories using various statistical tests. This approach is developed for the most updated CPT-based case histories from Ku et al. (2012), and SPT-based case histories from Idriss et al. (2010). Further, the logistic regression model is compared with the existing probabilistic models for CPT- and SPT-based case histories. This study shows that without considering the aforementioned uncertainties, the probability values can be significantly different and can give false sense of risk of liquefaction for a particular site of interest.

Dynamic compaction is a well-known method of soil improvement. In this method, a tamper falls from a specified height on the soil and results in energy spreading through its body, increasing horizontal and vertical stresses and relative density. In the present study, the finite element method is used for numerical modeling of dynamic compaction phenomenon. ABAQUS 6.10-1 software is used for two dimensional modeling of dynamic compaction in dry sands. A cap plasticity model is used as the constitutive model and the variation of peak ground velocity and peak ground acceleration are investigated. Considering PGV of 76 mm/s as the maximum value for mitigation of structural hazards in this research, critical distance of dynamic compaction process from adjacent structures is determined and applicable patterns are recommended. Moreover, the effect of initial soil density on the calculated critical distance is evaluated considering different SPT N-values. Based on the results, the effect of soil density on the critical distance is low and reduces with the increase in compacted alluvium depth.

Seismic settlement is a major cause of seismically induced damage to highway and railway embankments. Site investigation was conducted which showed road embankment always settled by shaking in areas above intensity VIII during an earthquake, and embankment settlement increased exponentially with the rise of seismic intensity in the areas from seismic intensity VIII to X. According to the discrete element method calculation, seismic settlement caused by the relative movement of particles occurs only when the ground motion intensity reached a certain magnitude, and settlement value would increase with the rise of the ground motion intensity. Large-scale shaking table model tests were used to verify the results of numerical calculation, which found that the longer the duration and the wider the spectral range of seismic waves, the larger the seismic subsidence.

This work aims to gain an insight into the dynamic stress responses of subsoil subjected to traffic loading. By introducing scalar potential functions, Helmholtz decomposition theorem, Fourier transform and inverse Fourier techniques are used to achieve an analytical solution to the three-dimensional dynamic stress in the saturated poroelastic ground, subjected to a harmonic rectangular moving load. The stress responses to dynamic characteristic of moving loading - including frequency and moving velocity - are investigated. It was found that both loading velocity and loading frequency produce significant influence on the dynamic stress. Some critical velocity has been observed and tends to result in the strongest dynamic response of stress.

This paper documents a series of large-scale shaking table experiments to investigate the dynamic response of liquefaction soil. Test results are discussed in terms of pore water pressure, earthquake-induced ground settlement, and acceleration of soil. The measured data show that, under strong ground motion, the model foundation was more sensitive to the ground motion whose low frequency component is more.TheArias Intensity of ground motion was associated with the peak of pore water pressure ratio. Under lower peak ground acceleration (PGA) ground motion, the magnification effect of acceleration response spectra appeared at the range of low-period component. However, in higher PGA ground motion, the model foundation shows obviously high frequency filtering characteristic. Observations in this study may serve as basis for engineers and researchers.

The passive surface wave survey method provides a non-invasive seismic site exploration approach for civil engineers. It works through measuring either human activity-induced ground vibrations or background ambient noise. It is superior to conventional geotechnical field testing approaches for site characterization over a large area. This paper reports surface wave survey case studies to demonstrate the application of this method to characterize local sites. Passive surface wave surveys were implemented in this research by collecting microtremors with designed sensor arrays. Measurements were processed to obtain the soil shear wave velocity profiles of the sites. Testing results were compared with borehole exploration data, which validated the passive surface wave survey measurements. Instrumentation, field testing design, and data analysis of this method were discussed. The paper envisages a great potential of the passive surface wave survey method in earthquake and geotechnical engineering applications in the urban environment.

Earthquake records of in-service, long-span bridges provide valuable insights into their seismic behavior and performance. In this paper, the strong motion records of arrays installed at two steel suspension bridges in a M4.8 earthquake are illustrated and preliminarily analyzed. The data reveal that the differences in the arrival times of peaks and valleys appear to be significant, which clearly illustrates the wave propagation effect. It is also shown that the differences in local soil conditions at different towers have significant influence on the spectra and time history of ground motions. The results suggest that the spatial variation of seismic ground motions induced by local site effect should receive more attention in seismic design and analysis of long-span bridges.

Based on Biot's wave equation, the dynamic response of a saturated half-space with impeded boundary to a moving load is studied theoretically. By using the Fourier transform method, the integral form solutions are obtained. At last, the influence of the boundary permeability to the dynamic response is analyzed by the numerical Fourier inverter transform. It shows that the influence of the boundary permeability to the dynamic response is associated with the permeability of soil and the velocity and frequency of the moving load.

Traffic-load-induced permanent settlement of road on soft subsoil should be given enough attention, especially for the Yangtze River Delta area. The traffic loading induces the degradation of the strength and stiffness and the accumulation of the excess pore water pressure. Based on the existing cyclic triaxial test results, a modified stiffness degradation model was proposed and the equation for calculating pore water pressure was built. Moreover, based on the modified stiffness degradation model and the layer-wise summation method, a new method is suggested to estimate the permanent settlement of road on soft subsoil under traffic load. The calculation results show that settlement increases rapidly in the early phase and then tends to be stable. The settlement of road is mainly composed of compression deformation of the 4th mud-siltly clay subsoil. Because additional dynamic stress of the 5th layer of silt is small due to the stress dispersion, its compression deformation is also very small.

Dynamic triaxial experiments of the saturated Nanjing fine sand are designed and accomplished. The slope of the relationship curves of the shear stress-shear strain rate of saturated sands under cyclic loading decreases with the build-up of the pore water pressure. Meanwhile, the apparent viscosity weakens gradually, and more and more strong fluid properties are shown. The rate-dependence of apparent viscosity is tested. The apparent viscosity decreases with the increase of shear strain rate. A typical shear-thinning fluid feature and power law relationship is discovered. A kind of fluid dynamic constitutive model was proposed for the saturated Nanjing fine sand. The effects of the cyclic stress ratio and the effective consolidation pressure on the flow characteristics of the saturated Nanjing fine sand were discussed

The proper selection of geoconstruction technologies under given site- and project-specific conditions is an important first step to ensure an adequate, sufficient and cost-efficient mitigation treatment plan. The objective of this study is to develop an interactive, readily accessible selection system for geoconstruction technologies for liquefaction mitigation. The interactive selection system generates a list of unranked geoconstruction technology candidates based on a user's input addressing several critical site and project-specific characteristics influencing technology selection for liquefaction mitigation. The influence of various critical factors on technology suitability is discussed. The value of this system is to provide a screening tool and resources on liquefaction mitigation using a variety of geoconstruction technologies.

At 14:46 (Japan Time) March 11^th 2011, a massive earthquake of magnitude 9.0 on the scale occurred on the Pacific coast from Sanriku to the Ibaraki coast. It was the most powerful earthquake known to hit Japan, and one of the five most powerful earthquakes in the world since modern record-keeping began in 1900. The earthquake triggered extremely destructive tsunami waves of up to 38 meters (124 ft) that struck Japan. In this study, the author investigated the characteristics of the Tohoku earthquake and tsunami based on the official information. The detailed earthquake response analysis was based on three sets of seismic strong motion data from K-Net by applying software viewave. The response history, response spectrum and Fourier spectrum were derived for in-depth comparison. Last, the investigation of seawalls was conducted to judge the seawalls' effect in defending tsunamis. The evidence showed that seawalls are ineffective when facing an extreme event, and it is necessary to rethink the design criteria.

Liquefaction is a common phenomenon of the sandy ground in an earthquake. It leads to the floatation of underground structures or subsidence of structure in the ground. Formerly, the phenomenon was associated with the main shock that lasts for a relatively short time. In recent years, however, it has been found that the bearing capacity of soils may also decrease during short-term seismic motions (aftershocks) that occur multiple times in the same way as in a long-term seismic motion. Crushed tiles are abundant in Aichi Prefecture (Japan), a center for the tile industry, and are one of the promising recycling materials for a countermeasure against soil liquefaction. This research investigates the effectiveness of these tiles as a countermeasure against liquefaction for a long-term seismic motion and short-term multiple aftershocks in case of small structures, and confirms their physical and mechanical properties.

An attempt has been made to estimate the seismic hazard at rock level in terms of PGA using a probabilistic approach. The detailed catalogue of historical and recent seismicity within a 350-km radius around the Ahmedabad region has been compiled and a new seismotectonic map has been generated. The completeness of the data should be checked before carrying out seismic hazard analysis; so, subsequently, it has been checked adopting different independent techniques. Finally, earthquake data has been analyzed statically and the seismicity of the region is evaluated by defining 'a' and 'b' parameters of the Gutenberg-Richter relationship. Eventually, a probabilistic hazard map corresponding to 500 and 2500 years of return period was developed for the region. Further, the Uniform Hazard Response Spectra with 5% damping was developed at both rock level and considering local site effects.

An improved response surface method is performed to study the reliability analysis of laterally loaded piles under pile head displacement failure. A development of p-y curves for laterally loaded pile response in ground is used to model the pile-soil system. The random variables used are the N_pu, N_po, λ, E₅₀, H, and E_pI_p. The CDF and PDF curves of laterally loaded pile head displacement obtained from the improved response surface methods are proposed and are in good agreement with the Monte Carlo method. The influences on the failure probability by a number of random variables are studied and discussed. The failure probability of the pile under the pile head displacement failure mode is sensitive to coefficients of variation of N_pu, H, N_po, E_pI_p and E₅₀. The coefficients of variation ofλ do not significantly affect the failure probability of the pile under pile head displacement failure mode.

The failure modes of suction bucket foundation - which have different length-to-diameter ratios - are proposed. The research shows that the failure modes have something to do with the length-to-diameter ratio. According to the rotation center position of the bucket foundation and distribution form of soil resistance - which have different length-to-diameter ratios - a three-dimensional finite element model is used to build the computational formula of the horizontal bearing capacity. Compared to the existing research, this paper aims at the saturated sand ground bucket failure mode - considering the length-diameter ratio of instability mode influence - establishing the different simplified calculating model according to the rotation center position as the boundary of the upper and lower parts of soil resistance distribution form. The effects of friction acting on the bucket's outer surface and the base bottom surface on the horizontal bearing capacity is also taken into account.

The paper aims at analyzing the factors which contain length and diameter of isolation piles, pile spacing and the distance S₁ between isolation piles and settlement-reducing piles, influencing isolation effects of isolation piles under surcharge load. The results summarized by eight laboratory model tests show that the maximum axial force and bending moment of settlement-reducing piles tend to decrease with the increasing length or diameter of isolation piles or with the declining pile spacing. Meantime, the length of isolated piles plays a significant role in diminishing the bending moment. The isolation effects of axial force and moment can be neglected when pile spacing reaches 8D. Apart from that, the isolation effects for axial force could be enhanced while diminishing the distance S₁. However, impacts on the moment isolation effects are not significant subject to the variation of distance S₁. This investigation could provide a good reference for the design and application of isolation piles.

A new kind of pile - named concrete-cored DCM pile - was developed in recent years. It is composed of precast core pile and deep cement mixing (DCM) column socket. The mechanisms and calculation method of bearing capacity for concrete-cored DCM pile in composite foundation are not clear. In this paper, plate load tests on single pile (PLT-I) and plate load tests on single pile in composite foundation (PLT-II) are conducted in Nanjing-Changzhou (NC) Expressway and Nanjing Surrounding (NS) Expressway. Based on the results of PLT, stress tests and CPT, the foundation improvement effect and bearing mechanisms of concrete-cored DCM pile were discussed. Finally, the calculation method for the bearing capacity of concrete-cored DCM pile composite foundation is proposed.

According to the situation of the shortage of the bearing capacity of the soft and thick covering stratum, the root-caisson foundation - a new type of foundation - was introduced. The construction procedure involves: (1) sinking a caisson with reserved holes in the side wall; then, (2) pushing prefabricated roots into the soil through the reserved holes by the jack after the caisson has been sunk to the design level; and (3) casting concrete to make sure that the roots are fixed with the caisson. The mechanism of vertical bearing capacity of root-caisson foundation was analyzed, and the improvement of bearing capacity due to the soil compaction and the bending resistance of roots was discussed. The self-balanced test method was utilized in the field tests to investigate the vertical bearing behavior of a root-caisson foundation with a traditional one. The results indicate that: (1) the roots are capable of activating a large range of soil to bear the load, and (2) with reasonable installation of roots, the ultimate bearing capacity of a root-caisson foundation is greatly larger than that of a traditional caisson foundation. Compared with the traditional caisson, the vertical bearing capacity of a root-caisson foundation could be increased by100%.

As the size of offshore structures has been increasing, the interest for foundation systems with large capacity is also rising. Along with this trend, studies are in progress on suction piles (widely used as mooring anchor systems) which can develop large capacity. In this paper, the concept of multiple suction pile anchors - which are composed of several suction piles connected in parallel - is introduced. Two types of multiple suction pile anchors are presented. In one type, two single-suction piles are connected. The other type is composed of three single-suction piles connected in parallel. The pullout behavior of the single-suction pile anchor and the two types of multiple suction pile anchors are investigated using numerical analysis. Numerical simulations using Abaqus software are performed and the three-dimensional model is deployed to duplicate the body shape of suction pile anchors. The load and displacement of the suction pile anchors are computed under continuous horizontal loading, and the pullout capacity of each type of suction pile anchors is evaluated.

In order to build new offshore breakwater on weak ground, prefabricated, thin-walled structures are often considered as its foundation. Integrated into a preliminary design study for a prototype breakwater to be built, a series of geotechnical centrifuge model tests are carried out to investigate the penetration behavior of a large, thin-walled, ellipse suction bucket into a layer of thick, muddy clay. The bucket foundation is first sunk into the muddy clay layer under its self-weight during the elevation of centrifugal acceleration to the appointed value. Then, an external sinking force is applied in flight on a bucket by a driving actuator of large travel. During this penetration stage, the internal compressive strains of wall and partition boards are measured against bucket displacement along with the external force applied. After penetrating the clay layer, the bucket base is rested upon a silty clay layer. It is found that a turning point occurred on the relationship curve of total resistance with penetration displacement, indicating the contact of the soil within bucket with its inner ceiling. Accordingly, the value of resistance at the turning point is specified as the critical resistance of penetration, which governs how much vacuum value is utilized in its embedding process by means of vacuum method. Also, the friction profile with penetration displacement of the outside wall and inner diaphragms of the bucket foundation are also analyzed.

This article presents procedures performed in order to investigate the behavior and capacity of suction caisson anchors. Primarily, literature surveys were conducted to gather pertinent information that could assist the study. Then, small-scale experimentation was performed using suction caissons having an aspect ratio of 2.0. Small-scale experimentation included both static and cyclic pull-out testing. Through static pull-out testing, the failure displacement, adhesion factor (α) and reversed-end bearing factor (N_c) were defined. Cyclic pull-out testing was then implemented to observe more convincing suction caisson anchor capacity by emulating the loading and unloading system due to wind and wave.

During the environmental loading of the wind turbine, the monopile is subjected to lateral load cycles which might cause an accumulated displacement of the wind turbine. This study aims at investigating the behavior of offshore monopile by presenting a 3D numerical model for soil-structure analysis which efficiently captures the fundamental mechanisms of dry and saturated granular soil behaviour. The parametric studies were performed to quantify pile displacement and determine the effect of relevant factors. Among others, the functions of the cyclic load amplitude and loading frequency were investigated along with the effect of irregular load patterns on the monopile-soil system. The monopile response is highly influenced by system densification and soil dilation resulting from soil stiffness increase and development of negative pore pressures at shallow depths, respectively.

Recently, design of pile foundation in liquefiable soil has drawn considerable attention because of extensive damage to marine structures, such as bridges and wharves, which occurred in earthquakes. One of the major factors which governs the safe design of pile foundations is the soil-pile interaction, which itself can be affected by nonlinearities such as pile yielding, gapping, and soil recompression. After running a fully coupled dynamic analysis in a finite difference program (FLAC-2D), gapping effects on pile-soil interaction are evaluated here. Pore pressure generation, liquefaction and energy dissipation are captured in a developed numerical model. The model and the process of computation have been verified with centrifuge test data. A number of analyses are conducted in two conditions - with and without gap formation - for a wide range of frequencies to evaluate the effect of interface nonlinearities. It is observed that consideration of gapping may result in striking changes in pile internal forces and critical sections as well as excess pore water pressures in the vicinity of a pile.

Soil-Structure Interaction (SSI) plays a significant role in seismic response of the structures by altering the dynamic properties of the system and increasing the lateral deflection which, in turn, could change the performance level of structures. In this study, in order to experimentally investigate the influence of different types of foundations on SSI phenomena, a series of shaking table tests has been conducted considering four different cases, namely: (i) fixed-base structure representing the situation excluding the soil-structure interaction; (ii) structure supported by shallow foundation on soft soil; (iii) structure supported by floating pile foundation in soft soil, and (iv) structure supported by end-bearing pile foundation in soft soil. Benchmark earthquakes - including the 1995 Kobe, the 1994 Northridge, the 1968 Hachinohe, and the 1940 El Centro earthquakes - are adopted. Results indicate that presence and type of pile foundations change the dynamic characteristics and behaviour of the superstructure which should be considered in predicting the damage level of structural and non-structural elements.

This paper focuses on the issues that riverbed scouring causes in piles and pier of a balanced cantilever box girder bridge during a seismic event. Finite element model of a 9-span balanced cantilever box girder bridge with ANSYS was developed for the analysis. Earthquake was applied both in parallel and perpendicular directions to the traffic of the bridge by single point response spectrum analysis while varying the riverbed scouring depth. Moment in piles increases 137% and 87% about original no scouring condition for earthquake in perpendicular direction of traffic and parallel direction of traffic, respectively. While the percent decrement of pier moment, about original no scouring condition, for earthquake in perpendicular direction of traffic and parallel direction of traffic is 59% and 67%, respectively. Capacity ratios of the bridge pile were also observed using CSiCOL and scouring depth at which capacity ratio exceeds 1 was calculated.

A multi-story parking building with steel frame was designed and constructed according to the Building Standards Law of Japanese architecture. This study is to investigate the seismic performance of the building during and fter a great earthquake that will definitely hit the central part of Japan in the near future. Special attention is paid to the differential settlement caused by the liquefaction and the long-term settlement after the arthquake. The analysis is carried out by 2D soil-water coupled dynamic/static finite element analysis using a program named as DBLEAVES (Ye, 2011). The input earthquake wave is a kind of 3 synchronization huge earthquake wave whose main shock lasts about 150s with a maximal acceleration of 182 gal. The ground behavior is described by Cyclic Mobility Model (Zhang et al., 2007, 2010, 2011). From the analysis, it is known that not only the liquefaction, but also the long-term settlement after earthquake, should be given serious consideration. Meanwhile, even if the seismic evaluation per the design code is OK, a detailed calculation may reveal the risk of under-estimation due to the shortcoming of such an overwhelming design code. In a word, sometimes an evaluation by an individual engineer will become crucially important.

In the present study, the dynamic behaviour of a hollow steel 3-pile group was investigated under vertical vibration by field vibration test and continuum approach analysis. The soil samples were collected from a borehole of 6.5-m depth. Both laboratory and field tests were performed to determine the soil properties. The forced vibration tests were conducted on a 3-pile group for different eccentric moments with static load of 10 kN. The time-acceleration response was measured for different frequencies using an accelerometer which was connected with a data accusation system. From the measured time-acceleration data, the frequency versus vertical displacement amplitudes were determined for different eccentric moments. The dynamic response of the pile group was analysed using the continuum approach of Novak, and the analytical results were compared with the dynamic test data. In the analysis, the interaction between two piles was used to formulate the group complex flexibility matrix from which the group stiffness and damping were deduced. It was found that the frequency-amplitude response obtained from the analysis was very close to the field response curve. The accuracy of the frequency response was found to be dependent on various nonlinear parameters like shear modulus ratio, thickness ratio and separation of soil-pile interface.

Piled raft foundations are often used when a raft foundation alone does not satisfy the design requirements or the raft settlements exceed allowable values. The addition of piles may improve both the ultimate load capacity and the settlement performance of the raft. In this paper, the behavior of a piled raft foundation is investigated using three-dimensional finite element analysis and 100-g centrifuge tests. The effects of a gravel layer on the maximum and differential settlement behaviors of piled raft is considered. Based on the results, the behavior of piled raft foundation is dependent on the thickness of the gravel layer and the particle size.

In reliability analysis, the crude Monte Carlo method is known to be computationally demanding. To improve computational efficiency, this paper presents an importance sampling-based algorithm that can be applied to conduct efficient reliability evaluation for axially loaded piles. The spatial variability of soil properties along the pile length is considered by random field modeling, in which a mean, a variance, and a correlation length are used to statistically characterize a random field. In each realization, the random fields are used as inputs to the well-established load transfer method to evaluate the load-displacement behavior of an axially loaded pile. Failure is defined as the event where the vertical movement at the pile top exceeds the allowable displacement. By sampling more heavily from the region of interest and then scaling the indicator function back by a ratio of probability densities, a faster rate of convergence can be achieved in the proposed algorithm. An example is given to demonstrate the accuracy and the efficiency of the proposed method. It is shown that the estimate based on the proposed method is unbiased. Furthermore, the size of samples can be greatly reduced in the developed method.

This paper presents an experimental program to investigate the failure behavior of belled pile under combined load. The article focuses on the interation of different kinds of load on bearing capacity of belled pile, bearing capacity resistance mechanism of belled pile and bearing capacity characteristics of yield envelope surface under the combined load. The measured data and phenomenon are discussed. As a result, the following behaviors have been clarified: the yield envelope curve on M=Hh plane is an ellipse approximately, which can be roughly estimated by an equation from V_m, H_m, and U_m. The failure curve on M-H plane also was an ellipse approximately. This ellipse can be determined by results of two laterally loaded pile tests. The interaction among vertical, lateral and moment load must be considered in the design of pile foundation.

As one of the primary pile styles in soft soil, the pretensioned spun concrete piles are applied widely in many fields, such as building engineering, traffic engineering, port engineering, and hydraulic engineering. However, there are many limitations in technology, such as its lower shaft resistance, lower resistance to bending and shearing, and poor linking manner and durability of connection between pile sections. A new-style pretensioned spun concrete nodular pile is introduced in this paper. The main construction technology, mechanical bonding manner and bearing character are improved aiming on the shortcoming of the traditional pretensioned spun concrete pile. Through the compressive and tensile static loading test, the bearing capacity of the new-style pretensioned spun concrete nodular pile is much higher than that of the ordinary one by at least 26%. Especially, its ultimate uplift resistance can be increased enormously, which the engineer is quite concerned about. Finally, the bearing mechanism and how the new nodular pile improve the skin friction are developed. So, the new-style pretensioned spun concrete nodular piles have many merits compared to the traditional one, which is helpful to its spread and application in soft soil.

The axial and lateral monotonic and cyclic behaviors of helical pile foundations were investigated and new innovative helical screw systems suitable for seismic loadings were developed and patented. More than 100 full-scale field load tests were conducted on instrumented helical screw piles installed in cohesive soil. The piles included: plain helical screw piles (P-HSP); grouted (G-HSPs); fiber-reinforced polymer FRP-G-HSPs; and reinforced grouted RG-HSPs. The RG-HSP piles' axial capacity was more than twice that for P-HSP with minimal reduction after cyclic loading, and their lateral capacity was more than 3 times the P-HSPs capacity. A 3-D finite element model was established. The results of 3-D finite element modeling were used to establish the load transfer mechanism and a design methodology for the considered piles.

Micropiles are the piles with small diameter which are used increasingly in recent years because of easier installation and less material than piles, while they provide targeted performance. This article focuses on finite element modeling of micropiles under dynamic loading, where mass concentrated is under consideration variable which is located in the central part above the micropile in order to stimulate the mass of superstructure and influence of inertial force. Numerical analysis has been performed by ABAQUS 3D finite element modeling software. Then, the performance of micropile - including lateral displacement and micropile bending moment - are investigated according to the mass super structure change under dynamic conditions. The environment of isotropic soil was considered by elastic behavior and implicit method has been used under dynamic conditions. Performed studies indicate that bending moment and lateral displacement of micropiles increase with the increase of mass super structure.

Solutions of cylindrical cavity expansion are used widely in geotechnical and tunnel engineering. Traditional cylindrical cavity expansion theory is based on the assumption that the lateral pressure coefficient K₀ = 1.0. In practical engineering - due to long-term deposition in the initial anisotropic stress state - in most cases, the lateral pressure coefficient K₀ of soil is not equal to 1.0. Based on the Unified Strength Theory (UST), elastoplastic solutions for cylindrical cavity expansion are deduced considering the variation of K₀. Case study results indicate that: (1) it is necessary to consider the effect of K₀; (2) traditional analytical solutions of cavity expansion, which are based on the K₀ = 1.0 supposition, overestimated the critical expansion pressure and ultimate expansion pressure; and, (3) underestimated the plastic zone field around the cavity.

Since the seismic performance of a modern subway station remains unclear, it is of urgent need to clarify it through a simple, yet rigorous method. So far, the pushover analysis is a powerful tool for evaluating the expected seismic performance of building and bridge structures. It is a static elasto-plastic method, so no complicated constitutive model is needed. In this paper, a static pushover analysis is conducted on a multi-story subway structure in Shanghai through the general purpose finite element code, ABAQUS. An inverse triangle displacement pattern obtained from non-linear dynamic time history analysis is determined as the lateral load pattern and is imposed on the side wall of the structure in pushover analysis. The damaged plasticity model and idealized elastic-plastic model are adopted for concrete and rebar, respectively, to trace the nonlinear behavior of the materials. The numerical results indicate that the deformations of some floors of the underground structure are different from those of a surface structure because of the large floor-to-column-stiffness ratio. Furthermore, the seismic failure mechanism of a subway structure is a global one, and the columns on the bottom floor are the vulnerable spots where flexural failure, rather than shear failure, occurs.

In recent years, pile driving adjacent to a slope often happens in the practice and thus, many accidents incurred. Due to the non-axisymmetric characteristics of pile driving boundary conditions, it is difficult to solve this problem by theoretical solution. In this paper, the Finite Element Method (FEM) is used to analyze the slope squeezing displacement under pile driving adjacent to slope. The results indicate that the size of the influence zone in which soil squeezing displacement is obvious continues to increase with the penetration of pile, and the displacement mode around pile changes as well. The soil adjacent to the pile body settles downward under the radial compression and side friction. However, beyond a certain distance to pile, uplift displacement of the soil is observed under the free boundary of surface and slope. After the pile reaches the bottom surface of the slope, the subsequent pile sinking has little influence on soil squeezing displacement. The experimental results:(1) reveal the soil squeezing performance caused by pile driving adjacent to slope and the mechanism for slope deformation, and (2) provide reference for designing practical engineering, setting construction parameters and controlling soil squeezing displacement.

Raft foundations are the favorite choice for most of the designers; but nowadays, due to constraints of cost increment decreasing availability of land because of rapid industrialization & urbanization, there is growth in the vertical direction resulting in many high-rise buildings going up. This has resulted in heavy load, complicated stress conditions, limitation of bearing capacity of soil, and settlement of high-rise buildings. As a solution to the settlement problem of high-rise buildings, a number of piles are used and a new type of foundation - called a piled raft foundation - is coming up in a big way. In some designs, approach piles are used for reducing the settlement and a load is carried by raft only. Another design method still concentrates on providing adequate axial capacity from the piles to carry the structural load and the bearing capacity of the raft is neglected. In both the design approaches, the piled raft foundation becomes uneconomical as bearing capacity of raft and pile are not utilized in the single design approach. This shows that design rules and standards for piled-raft foundations are not well established. The interesting observation in the Poulos-Davis-Randolph (PDR) design methodology for piled raft, but using a simple stiffness formula, the piled raft foundation can be designed and analyzed. It is observed that an increase in pile length leads to increase in the settlement, which is contrary to the practical observation. It is because the stiffness of any structural member in our case pile decreases with increase in length for a given diameter. This can be avoided by using a length of pile up to depth of fixity. The length of pile below fixity, due to surrounding soi,l can be neglected. This length of pile above depth of fixity is also called free-standing length of pile. This free-standing length can be calculated using Indian standard on pile. By using simple stiffness formulae in PDR methodology, the piled raft design can be simplified.

To establish rational design and construction process, two-dimensional model tests are carried out varying the length and inclination of ground anchors. Numerical simulations with finite element method using FEMtij-2D are also carried out for the same scale as the model tests. Subloading t_ij model (Nakai and Hinokio, 2004) is used in the analyses to model the ground material. It has been revealed that installation of a longer anchor at the bottom part of the excavation area is very effective in reinforcing the effects of the earth retaining wall. Inclination of the ground anchor also has a significant effect on the displacement of the backfill ground and deformation of the retaining wall. The finite element analyses show very good agreement with the results of the model tests.

To increase bearing capacity of a foundation, geosynthetic is laid beneath the foundation. In previous research, the authors investigated the reinforcement mechanism by changing the length and the laying depth of the reinforcement (Nakai et al, 2009). In the present study, to get more bearing capacity, the reinforcing effect in the case that each edge of the reinforcement is fixed with the soil is investigated. For this purpose, 2D model tests and the corresponding non-linear finite element analysis are carried out. In these tests and simulation, the depth of the reinforcement is changed under constant length of reinforcement. Reinforcing effects, under concentric and eccentric load, are discussed. It is revealed that a significant increase of the bearing capacity is observed in the model tests when the reinforcement is set up in the ground with an appropriate depth under both concentric and eccentric loads. The results of numerical simulation - in which the stress-stain behavior of the soil and the frictional behavior between soil and reinforcement are properly taken into consideration - show good agreement with the observed results.

In order to reduce buckling problems of railway ballasted tracks, efforts have been made to improve lateral resistance of sleepers. There has been a lot of research on the development of new shapes of sleepers which may increase lateral resistance. However, detailed investigation on the mechanism of improvement has not been studied. Based on the above, a series of model tests was attempted in this study. Six types of sleepers were prepared for model tests. Single-sleeper pullout tests and track panel pullout tests were conducted on the sleepers. The model test results revealed that lateral resistance of the sleepers is significantly affected by their shapes. The idea that the lateral resistance measured at a horizontal displacement of 2.0 mm in full-scale (or 0.4 mm in 1/5-scale) single-sleeper pullout tests corresponds to that in track panel pullout tests is only valid for limited conditions. This is because of the piled group effect in track panel pullout tests, which affects the lateral resistance. Because the degree of the piled group effect is controlled by the ratio of the sleeper width to the sleeper spacing, a significant reduction of lateral resistance may be observed in track panel pullout tests depending on the sleeper type.

This paper presents the pullout capacity of steel chain embedded in pure sands using 1g lab-scale model test. The anchor chain made of steel is often embedded into sands connecting anchor to floating structures. Even though the lateral or vertical forces applied to the floating structures are resisted by both anchor and anchor chain, most research has focused on the capacity from the anchor system, not from the anchor chain. In the model test, a steel anchor chain was embedded into Jumunj in sands and horizontally pulled out to failure. The pullout capacity of the anchor chain was divided into frictional resistance and passive resistance, and the necessary factors to estimate each component were proposed using test results. It was found that the maximum pullout capacity of anchor chains increased as the embedment depth increased. The contribution of passive resistance to the total pullout capacity was calculated to be as much as 81~93%.

Stability assessment of submarine slopes subjected to wave-induced pressure is a necessary part of the design process for pipelines or structures in the marine environment, as the instability or liquefaction of the seabed induced by waves can cause significant displacement. To evaluate the stability of seafloor slopes, the upper bound approach of limit analysis combined with strength reduction technique is presented to solve the factors of safety (FS) of seafloor slope considering wave-induced pressure. First, the analytical formula for the stability of seafloor slope under static water condition is derived and the stability is analyzed. Then, waved-induced pressure is considered to act on the surface of slope as an external load to analyze the effects on the stability of seafloor slope. Compared with the results from elasto-plastic finite element method, the present solutions are validated. A series of calculations by changing parameters are carried out. The results show that the effects of wave have some disadvantages on the stability of seafloor slopes and this kind of affect will expand in shallow seas or in the situation of huge waves.

A geogrid reinforced retaining wall is a relatively new flexible retaining structure. However, its dynamic behavior and seismic resistance mechanism under earthquakes are not clear at present. A laminar shear container was used to install the test model of geogrid reinforced retaining wall. Its seismic response was investigated by a large-scale shaking table test. The similarity criterion of the model was confirmed by the Froude constant of Bockingham Π theorem in dimensional analysis theory. A series of variables - such as acceleration, horizontal displacement of the wall, seismic subsidence of reinforced zone and unreinforced zone under different waves - were measured. The measured results show that the reinforced wall model has different responses under different earthquake motions. Accelerations of the wall were amplified under earthquake wave caused by far field, while the distribution of spectrum is symmetric and the largest spectrum value was presented on the top of the wall. The displacement of wall top is the largest along the reinforced wall height, and the seismic subsidence of the reinforced zone is smaller than unreinforced zone, which indicates the geogrid effect on the reinforced soil retaining wall.

The concept of seismic active earth thrust is essential for the safe design of earth retaining walls in the seismic zone. In the proposed method, reaction along the planar failure surface is obtained using Kötter's (1903) equation. Further, limit equilibrium method is effectively used to compute active earth thrust considering pseudo-static condition with both horizontal and vertical seismic co-efficients. An attempt is made to locate the point of application of active thrust using moment equilibrium condition in c-φ backfill. This study is further extended to compute active earth thrust considering pseudo-dynamic condition which is more realistic in representing time and phase difference within the soil backfill. The effects of various parameters - such as angle of internal friction, wall friction angle, and angle of backfill inclination, horizontal and vertical seismic co-efficient, shear wave, and compression wave - are discussed. It is seen that seismic active earth thrust decreases with increase in both friction angle and cohesion. Further, active earth thrust increases with increase in horizontal seismic co-efficient and surcharge angle. The results obtained by the trial and error method are underestimated by 2% as compared to the results obtained from the pseudo-static and pseudo-dynamic analytical approaches suggested by Sharma and Ghosh (2010). Similarly, predictions made in case of static approach are in good agreement with results obtained from analytical approach suggested by Sharma and Ghosh (2010).

In recent years - due to its own characteristics of the embedded anti-slide pile in the slope support - it is a widespread application and is becoming a main way of slope support. In the static case, the research of the embedded anti-slide pile has already been relatively mature, but the research in dynamic action is still less. This paper completed the design of the slope's shaking table model test through the importation of different type, frequency, amplitude of seismic wave and the white noise excitation, to discuss the dynamic characteristics and regularity of dynamic response of embedded anti-slide pile under the action of earthquake, as well as the influence of the motion parameters toward the dynamic characteristic and dynamic response. Then, simulate this model, and draw some meaningful conclusions, to better guide slope seismic design, and embedded anti-slide pile to better guide slope seismic design, and has a wide range of application prospect.

The seismic stability of an earth slope reinforced with a row of anchors is analyzed within the framework of pseudo-static approach. First, the upper-bound approach of limit analysis combined with strength reduction technique is employed to solve the safety factor and the corresponding critical log-spiral failure mechanism for a given slope. Then, the slope reinforced with a row of anchors is considered and the analytical expressions for calculating the safety factor are derived. The reasonability of solutions is fully verified by comparison with the known solutions from different methods. Further, a pseudo-static seismic load is applied to the anchored slope, and the new analytical formula is also built. Finally, the parametric study is carried out to illustrate the effect of anchor orientation, anchor position, and seismic loading on slope stability.

The Pastor-Zienkiewicz-Chan model, based on the generalized plasticity theory, can simulate the stress-strain relationship of soils quite well. Based on the triaxial tests of the filling materials of an earth-rockfill dam, model parameters were obtained through fittings of model and test data. The fitting curves showed that the generalized plasticity model is capable of simulating the mechanical behaviors of rockfill materials. The model was then implemented into a finite element code to carry out 3-dimensional static and dynamic analyses of the earth-rockfill dam. Permanent displacement of the dam was gained and discussed. The results show that the generalized plasticity model can give a good description of dynamic response characteristics of earth-rockfill dams.

Earthquakes and subsequent rainfall infiltration often easily trigger a landslide, such as the "10.4" Yiliang slope incident in Yunnan Province. In the present study, based on detailed on-site survey, indoor rainfall tests were designed to investigate the different hydraulic responses of initial and seismic slopes to rainfall. To further assess the joint effects of earthquake disturbance and subsequent rainfall on slope failure, the rainfall unsaturated seepage fields of the above two types of slope were simulated separately. Then, based on the pore water pressures obtained in the above calculations, the safety factors of the slopes were calculated using a finite element method. The results showed that the seismic slopes are inclined to rainfall infiltration, which significantly increased the pore water pressure and induced the rise of ground water. Moreover, the factor value of seismic slope safety suffering subsequent rainfall was shown to be smaller than the undisturbed one. Finally, a deeper potential failure zone and wider soil mass sliding range evidently illustrated the combined effect of earthquakes and rainfall on the triggering of slope failure.

This paper presents a study of dynamic responses of underground structures in liquefiable soil. Analysis is performed using the open source finite element framework OpenSees, and a novel, three-dimensional, cyclic plasticity model for the analysis of large post-liquefaction deformation was used. 2D and 3D numerical analysis were performed respectively to compare the stress and deformation of the underground structure. Computation results showed that the 2D calculation may overestimate the displacements of the structure and underestimate the dynamic stress responses of the structure. Through 3D analysis, parametric studies on the effects of slope angle of the ground and buried depth of the underground structure were conducted.

Two existing methods for estimating in-situ coefficient of consolidation in the horizontal direction (c_hp) from "non-standard" piezocone dissipation curves (initial u increased for a short period and then dissipated) are applied to the test results in 11 sites in Japan, China, USA, UK, Italy and Canada. One method is correcting t₅₀, the time period of measured pore water pressure (u₂) dissipated from its maximum value to 50% of the maximum value (t_50c method), and another is extrapolating √t (t is elapsed time) ∼u₂ curve (√t method). The analysis results show that, for most cases, t_50c method results in higher c_hp value than that of √t method. It is reasoned that c_hp value from t_50c method is closer to the field "true" value. Comparing c_hp values from t_50c method with the corresponding laboratory measured coefficient of consolidation in the vertical direction (c_v) indicates that for most data c_hp/c_v ratios are varied from about 3 to about 100. The data from six (6) sites in Jiangsu, China showed higher c_hp/c_v ratio which implies that the sites may have higher anisotropic consolidation properties.

GeoWall - a reinforced retaining wall - is a common structure in the field of civil engineering. It is often applied in highway and railway projects. In the United States, the GeoWall competition is quite an important part of the ASCE student conference competition. In this competition, the structure of GeoWall is simplified as a model consisting of post-board paper face, kraft paper reinforcements and sand in a box. By participating in such games, students could learn more about GeoWall structure and gain their own thoughts towards the calculation assumptions and methods which would even be applied in real construction cases. In this paper, the author would combine the competition experience to expatiate the design assumption, method and experience and make a further analysis combined with soil mechanics and real engineering projects.