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As a common lithology material of tunnel surrounding rock, rock mass in fault fracture zones is often wetted by groundwater to produce extensive wetting-induced deformation, which threatens the long-term stability of underground engineering. To investigate the wetting-induced deformation behavior of such surrounding rock mass and to explore effective maintenance and control techniques, the strength and wetting deformation characteristics of completely weathered granite from a tailrace tunnel to be excavated in the fault fracture zones were studied using a large-scale triaxial shear apparatus. Under the same confining pressure, the natural and saturated specimen strengths were slightly different, but their deformations were very different, especially under low confining pressures. After wetting, the wetting-induced deformation of the specimens was affected mainly by confining pressure and stress level, and the deformation was more sensitive to the stress level than the confining pressure. The wetting-induced deformation process presented significant time-dependent characteristics with stable creep. A new time-varying effect model was established based on the experimental results, which enabled an accurate simulation of the wetting deformation of the rock mass through a comparison with the experimental results. A criterion to judge the deformation stability of such surrounding rock was proposed from the perspective of an engineering application. These results allow for further study of the deformation mechanism and control measures for underground deformation by wetting.

Field evidence revealed that buried cast iron water pipes can deteriorate through large localized corrosion patches with lengths greater than 1 m, formed by a cluster of small pits. This study inve...

The deep fissured rock mass is affected by coupled effects of initial ground stress and external dynamic disturbance. In order to study the effect of internal flaw on pre-stressed rock mechanical responses and failure behavior under impact loading, intact granite specimens and specimens with different flaw inclinations are tested by a modified split Hopkinson pressure bar (SHPB) and digital image correlation (DIC) method. The results show that peak strain and dynamic strength of intact specimens and specimens with different flaw angles (α) decrease with the increase of axial static pressure. The 90° flaw has weak reduction effect on peak strain, dynamic strength and combined strength, while 45° and 0° flaws have remarkable reduction effect. Specimens with 90° flaw are suffered combined shear and tensile failure under middle and low axial static pre-stresses, and suffered shear failure under high axial static pre-stresses. Specimens with 45° and 0° flaws are suffered oblique shear failure caused by pre-existing flaw under different axial static pre-stresses. Besides, based on digital image correlation method, it is found that micro-cracks before formation of macro fractures (include shear and tensile fractures) belong to tensile cracks. Tensile and shear strain localizations at pre-existing flaw tip for specimen with 45° and 0° flaws are produced much earlier than that at other positions.

This study proposed a random Smoothed Particle Hydrodynamics method for analyzing the post-failure behavior of landslides, which is based on the Karhunen–Loeve (K-L) expansion, the non-Newtonian fluid model, and the OpenMP parallel framework. Then, the applicability of this method was validated by comparing the generated random field with theoretical result and by simulating the post-failure process of an actual landslide. Thereafter, an illustrative landslide example was created and simulated to obtain the spatial variability effect of internal friction angle on the post-failure behavior of landslides under different coefficients of variation (COVs) and correlation lengths (CLs). As a conclusion, the reinforcement with materials of a larger friction angle can reduce the runout distance and impact the force of a landslide. As the increase of COV, the distribution range of influence zones also increases, which indicates that the deviation of influence zones becomes large. In addition, the correlation length in Monte Carlo simulations should not be too small, otherwise the variation range of influence zones will be underestimated.

In order to advance the reliability analysis of practical engineering problems, a simplified iterative algorithm for forward and/or inverse first-order reliability method (FORM) is presented in this paper. The approach extends the well-known HLRF algorithms that are conventionally formulated in the uncorrelated standard normal space (u-space) into the correlated nonnormal space (x-space). Because the simplified algorithms are self-contained in x-space, the tedious mathematical transformations of random variables between statistical spaces as well as the inversion of Jacobian matrix for gradient vectors are not required, which are desirable for practitioners to implement FORM within standalone numerical codes. The convergence of the simplified iterative algorithms can be improved by properly adjusting the step length during the iterative computations. Verifications of the proposed algorithm are illustrated through a highly nonlinear problem for both forward and/or inverse reliability analysis. Based on the proposed inverse FORM algorithm, the geotechnical reliability-based designs (RBD) of a strip footing and an earth slope are performed and some insights gained.

The seismic response of a tunnel lining structure is essential for its safety design and construction. The objective of this study is to investigate the seismic response of a tunnel lining structure embedded in a thick expansive soil stratum. First, the deformation and internal force characteristics of tunnel lining structure under seismic action are evaluated from a theoretical perspective. Second, a finite element (FE) analysis is carried out of the seismic responses of the tunnel lining structure and ground stratum. In the FE analysis, the bolted connections in the tunnel lining structure are simulated using the local stiffness reduction method (LSRM). The LSRM reduces the stiffness of the lining segments affected directly by the bolted connections using a stiffness reduction coefficient (SRC), while leaves the stiffness of the rest of the lining segments to remain to be unchanged. The results indicate that under the effect of transversal waves propagating in the direction perpendicular to tunnel axis, the transversal displacement characteristics of the tunnel lining structure are almost identical to that of the surrounding soil stratum. They both decrease with an increase in buried depth. The circumferential distributions of shear force, bending moment, and axial force in lining segments are varied, but the magnitudes of them increase with an increase in SRC.

In order to explore more economic filling alternatives than typically used graded gravel + 5% cement in a high-speed railway transition zone, engineering properties of graded gravel (without cement) and A, B group filling (well graded coarse-grained soil with less than 30% of fine-grained soil) were tested. This is followed by the establishment of a 3D vertical coupling dynamic model of a tunnel-culvert-tunnel transition section based on the D'Alembert’s principle of energy weak variation and the Lagrange scheme. The model results have been validated against the in situ measurements. The analysis from the model show that both graded gravel and A, B group filling are well-graded with high strengths, and the dynamic responses of the roadbed supported by the two fillings are both less than allowable values at the speed of 350 km/h. However, the curves of vertical displacement along the longitudinal transition section are great like a shape of “W” with the A, B group filling in the transition zone. Therefore, the graded gravel is recommended to be more suitable than the A, B group filling for the studied tunnel-culvert-tunnel transition zone. This recommendation may be applicable to the case with a rock subgrade underneath to support the transition zone. Comparatively, for a soil subgrade under the transition zone, our results indicate that graded gravel + 5% cement is still the best filling material, while the other two less stiffer filling materials would result in considerable fluctuations to the roadbed surface.

Most of the research studies on the improvement of expansive soils are focused on reducing their expansive properties; however, there are few studies on the impact of the soil compressibility after the improvement. In this paper, through indoor high-pressure consolidation tests, the recent microbial-induced calcium carbonate precipitation (MICP) technology is studied to improve the compression characteristics of the expansive soil. The significant effect of different microbial concentrations (achieved by different number of treatments) on the compression deformation is revealed with the hyperbolic function that involves two parameters with clear physical meanings. In particular, after 6 times of treatment with the microbial solution, the compression characteristics of the expansive soil reach the best improvement effect; continuing to increase the number of microbial treatments is, otherwise, not conducive to improving the soil compression performance. Also, a dramatical increase of the structural strength of the microbial-treated expansive soil is presented and investigated. Moreover, we performed a scanning electron microscope (SEM) experiment and confirmed the existence of crystals due to mineralization. This study shows that MICP is an effective and environmentally friendly means of reducing the compressibility of the expansive soil.

Dynamic response of a bridge&ndash, embankment transition is determined by, and therefore an indicator of, the coupled train&ndash, track&ndash, subgrade system. This study aims to investigate the approach of coupling the train&ndash, subgrade system to determine the dynamic response of the transition. The coupled system is established numerically based on the weak energy variation, the overall Lagrange format of D&rsquo, Alembert&rsquo, s principle and dynamics of the multi-rigid body, which is verified by in-site measurements. With this model, the influence of rail bending, differential settlement and other factors on the dynamic performance of the transition system is analyzed. The results show that when the train driving speed is 350 km/h, basic requirements should be satisfied. These requirements include that the irregularity bending of the bridge&ndash, embankment transition section should be less than 1/1000, the rigidity ratio should be controlled within 1:6, and the length of the transition section should be more than 25 m. In addition, the differential settlement should not exceed 5 mm. Among these factors, the differential settlement and the bending of the rail surface are the main ones to cause the severe dynamic irregularity of the transition section. Our analysis also indicates a requirement to strengthen the 18 m and 25&ndash, 30 m distance from the abutment tail and the bed structure.

Because of the large amount of gravel with particle sizes over 40 mm in the soil-rock mixture (SRM), it is impossible to determine its California Bearing Ratio (CBR) via the indoor test method, which is a key parameter for designing the backfill in underground mined cavities or the road subgrade constructed with SRM. In this paper, X-ray computed tomography (CT) scanning and 3D reconstruction technology were used to construct the 3D structure of SRM particles with a particle size greater than 5 mm. Based on the vertical vibration test method (VVTM) and PFC3D, the numerical simulation method (NSM-CBR) of SRM was established. The CBR of the SRM with a maximum particle size over 40 mm (SRM-G) was studied by NSM-CBR, and the effects of factors such as maximum particle size, soil content, and large-size particle content (d ≥ 40 mm) on the CBR were investigated via NSM-CBR. Based on the laboratory tests and NSM-CBR, the prediction model and the determining method of CBR of SRM-G were established and verified. The results show that the maximum deviation between the CBR obtained from NSM-CBR and laboratory tests was 7.4%. The CBR of SRM-G decreases linearly with the increase in soil content and increases with the increase in maximum particle size and large-size particle content. The practical project shows that the maximum deviation between the predictive and measured values of the CBR of SRM-G was less than 1.5%, indicating that the prediction model and the method established in this paper have high reliability.

During the excavation of the Minxian tunnel, problems of large deformations of surrounding rocks and failure of support structures appeared frequently, which caused serious influences on construction safety and costs of the tunnel. Based on laboratory analysis of mineral composition and field investigations on deformation characteristics of the surrounding rocks, the large deformation mechanism of surrounding rocks of the tunnel was considered as water-absorbing swelling molecules of carbonaceous slate and stress-induced asymmetric structural deformations of the surrounding rocks. The structural deformations of surrounding rocks mainly include bending deformation, interlayer sliding, and crushing failure of local rock blocks. Then, a new constant resistance and yielding support technology based on the constant resistance and large deformation (CRLD) anchor cable was proposed to control large deformations of surrounding rocks. The field tests and deformation monitoring were carried out. The monitoring results showed that compared with original support measure, the surrounding rock deformations, stresses of primary supports, and permanent lining using new support technology decreased greatly. Among them, the maximum deformation of surrounding rock was only 73 mm. The effects of field application and results of deformation monitoring showed that the new support technology can effectively control large deformations of the surrounding rocks in the Minxian tunnel.

By virtue of its high speed, steadiness, and quality experience, high speed railway (HSR) has grown rapidly. During that development, problems such as dynamic irregularity in the bridge–embankment transition have been exposed and have aroused keen attention. To study dynamic performance in bridge–embankment transition, field dynamic tests under 120 high speed vehicles running at speeds of 5–360 km/h were carried out. Then, processed signals were obtained from the original signals by a series of signal processing methods such as wavelet soft threshold filtering, Newton-Cortege integration, and five-thirds smoothing. Moreover, the statistical test data were analyzed in the time/frequency domain to obtain the frequency characteristics, the rules governing changes in dynamic responses along the longitudinal and depth directions, and the rules governing changes in dynamic responses with train speed, train running direction, vehicle axle load, and adjacent load. The results showed that (i) the concentration range of the first two main frequency was generally 0–50 Hz, (ii) particular attention should be paid to sections 7.5 m, 13 m and 25 m from the abutment tail, and (iii) importance should be attached to the bed surface layer. As well, 275 km/h was the critical train speed and acceleration was a sensitive dynamic index. Finally, the dynamic responses showed that a bridge–embankment transition with the subgrade filled with graded gravel + 5% cement satisfied design and operation requirements at speeds of 5–360 km/h.

Periodic inspection of pipeline conditions is an important asset management strategy conducted by water and sewer utilities for efficient and economical operations of their assets in field. The Level 1 pipeline condition assessment involving resistivity profiling along the pipeline right-of-way is a common technique for delineating pipe sections that might be installed in highly corrosive soil environment. However, the technique can suffer from significant perturbations arising from the buried pipe itself, resulting in errors in native soil characterisation. To address this problem, a finite element model was developed to investigate the degree to which pipes of different a) diameters, b) burial depths, and c) surface conditions (bare or coated) can influence in-situ soil resistivity measurements using Wenner methods. It was found that the greatest errors can arise when conducting measurements over a bare pipe with the array aligned parallel to the pipe. Depending upon the pipe surface conditions, in-situ resistivity measurements can either be underestimated or overestimated from true soil resistivities. Following results based on simulations and decoupling equations, a guiding framework for removing pipe influences in soil resistivity measurements were developed that can be easily used to perform corrections on measurements. The equations require simple a-prior information on the pipe diameter, burial depth, surface condition, and the array length and orientation used. Findings from this study have immediate application and is envisaged to be useful for critical civil infrastructure monitoring and assessment.

This paper presents a novel unified model coupling soil volumetric hardening and water retention. The volumetric hardening law is formulated using the effective stress concept and can be applied to various soil types with unified formulations. This law also considers the influence of stress-induced anisotropy, and provides an enhanced prediction of soil response under elevated stress levels and loading–unloading cycles. Furthermore, this law is coupled with a new Soil Water Retention Curve (SWRC) model by considering the dependency of SWRC on the volume change. The new SWRC model captures the hysteretic nature of the water retention, and offers an improved prediction of the hydraulic path for high suction levels. The SWRC model also allows capturing the experimentally observed reduction in the degree of saturation which may occur during the early compression stage under constant suction. With the coupling of the volumetric hardening law and the SWRC model, the unified model is finally developed. The unified model is validated with reasonable accuracy against a wide range of experimental data reported in the literature on clay, silt and sand.

Based on the 1–3 identical high-rise buildings with pile-raft foundation, a series of building-site two-dimensional finite element analysis models with different building spacings is established. Then, considering the nonlinear characteristics of soil and structure, the static-dynamic coupled numerical simulations are conducted to study the structure-soil-structure interaction (SSSI) under different ground motion. The results show that: 1) Adjacent high-rise buildings have the most unfavorable impact on the peak acceleration of the 1/4–1/2 height floors of the middle building, and increase the normalized response acceleration spectra value of acceleration near the second natural period of the structure; 2) Adjacent high-rise buildings have the most significant impact on the inter-story drift of the top, bottom and basement of the middle building; 3) Adjacent high-rise buildings redistribute the total horizontal shear force of the pile top of the middle building among the pile foundations, so that the peak value of the pile top shear force of each pile changes significantly, which is extremely unfavorable to the seismic safety of the structure. It should be taken seriously in the seismic design of structures. In addition, the structure spacing that results in favorable or unfavorable effects is discussed, and the reasons for the impact are analyzed.

The stability of rock engineering is generally dominated by existing seepage , particularly the seepage evolution due to the rock masses damage. However, the current research generally overlooks the seepage-damage coupling when studying the hydraulic-mechanical coupling effect in rock masses. This study aims to propose a dual-medium model, including equivalent continuous and discrete fracture media to study the coupled seepage-damage effect in fractured rock masses . The dual-medium seepage model considers the substantial water storage of the fracture network and the high conductivity of major large-scale fractures. Also, the seepage evolution is constructed to be a function of stress, seepage pressure and length of crack propagation in the rock mass. To illustrate the new model's application, a case of high-pressure water injection in a coal seam has been investigated to reveal the damage evolution in the coal seam. The results indicate that during the initial stage of the water injection, the seepage pressure in the discrete fracture medium increases faster than that in the equivalent continuous medium. Moreover, the seepage pressure difference between the two media gradually decreases with the increase of the seepage time, eventually forming a stable seepage field in the coal seam. Notably, the high-pressure water injection in the coal seam significantly affects the distribution of the coal seam's stress field, resulting in the effective minimum principle stress changing from compression to tension states. Also, during coal seam water injection, the damage zone and major fracture apertures in the coal seam gradually increase with increasing injection time .

Openings including their size, shape and distribution in rock play a significant role in the performance of rock related structures. The well-established knowledge in this area can contribute to the engineering practices, for example, underground space design, planning and optimisation in Civil and Mining Engineering and wellbore stability in Drilling Engineering, among others. Thus, understanding the failure mechanism of rock with openings is theoretically and practically meaningful. Laboratory testing on rock or rock-like materials with openings have been studied extensively in the literature, which, however, primarily focuses on the cracks/fractures. In this paper, a comprehensive numerical study on the effect of non-banded openings, i.e., circular, rectangular, and triangular opening, on the rock mechanical behaviour is performed using a hybrid continuum-discrete element method. It is revealed that the proposed simulation method can reproduce reasonably the crack initiation and propagation, and predict well the change of the mechanical behaviour due to the openings. In addition, the influence of the opening shape and opening ratio (=area of opening/specimen area) on the mechanical behaviour is also investigated.

We examine a new continuum micromechanical approach to predicting the macroscopic mechanical responses of Haubourdin chalk under various load conditions. The approach is based on a simple breakage model that accounts for an evolving microstructural degradation through coccosphere crushing with only five physically meaningful parameters and one grading index. The model correlates the intrinsic failure mechanisms including the coccosphere crushing, pore collapse and plastic shearing that are identified by corresponding internal variables within thermodynamic framework. On this basis, numerical predictions of the stresses and strains are examined against their experimental counterparts as well as the results from an existing continuum model. Parametric studies are further conducted to investigate the effect of the model parameters. The favourable agreements in various conventional and complex compression tests indicate a satisfactory performance of the breakage model, highlighting the importance of capturing the microscopic degradation mechanisms when building a constitutive model.

To understand the high temperature effects on the mechanical and failure behaviors of rock, uniaxial compression tests were carried out on granite specimens containing three pre-existing holes using a rock testing system. Based on the experimental results, the influences of testing temperature on the physical and mechanical parameters of granite were analyzed in detail. An obvious color change of tested granite occurs from gray at room temperature to reddish after 450 °C and to red-brown after 900 °C high temperature treatment. The granite volume increases, mass decreases and density decreases with increasing testing temperature. As the temperature increases, the peak strength first increases and then decreases, while the elastic modulus decreases. However, the peak strain changes slightly before 450 °C, increases dramatically up 450 °C. As the bridge angle increases, the mechanical parameters of granite specimens first decrease and then increase. And then, the crack initiation, propagation and coalescence behavior of granite specimens after high temperature exposure was investigated using an acoustic emission (AE) and photography monitoring technique. The cracking process shows that the propagation of crack from the surface of holes leads to the coalescence between adjacent holes. A large AE count and a stress drop are observed during the crack initiation and propagation. The failure modes can be generally classified into three categories: splitting mode, shear mode and mixed mode and they are closely related to heat treatment temperature and bridge angle. Finally, the mechanism causing the differences in the mechanical parameters observed with increasing temperature was discussed based on the SEM observations.

Pitting/patch corrosion is a major and common cause of leaks and (or) bursts in cast iron (CI) pipes that consist of over 50% of global pipelines. The determination of the remaining life of a CI pipe is a major challenge facing water utilities requiring an estimate of the impact of pitting corrosion on the degradation of structural pipe capacity. This paper uses an efficient finite element analysis (FEA) to model the behaviour of large diameter CI pipes with natural or simulated corrosion pits and patches. The test results were obtained through laboratory pressure testing. Laser scanning was used to develop three dimensional geometric models of pipe specimens for direct use in the numerical modelling. The CI material was simulated by a non-linear hyperbolic elastic model (termed MHM-CI) recently developed by the authors for CI pipe modelling. The numerical results showed that the proposed FEAs with the MHM-CI model are reasonably capable to predict the measured responses with increasing water pressure, importantly at the critical pipe corrosion patches, such as hoop strains, initiation of leak and burst failures. The initiation of fracture was explained by material failure purely by tension, which can form a crack that could lead to water leakage. Final burst possibility was modelled by using a simplified fracture mechanics approach to determine the critical crack length for spontaneous fast fracture as in a burst. Our numerical findings suggest that the proposed simplified numerical approach may be used to determine whether a corroded cast iron pipe would leak before break provided that the corrosion condition of the pipe and the relevant material properties are available. However, the window of time for leak before break would require further testing since this would be governed by sub critical fracture growth subject to repetitive external and internal pipe loadings.

Cast iron (CI) pipes were widely installed as water mains and service connections in the last century and still large numbers of CI pipes remain in service. However, many CI pipes are becoming aged and severely corroded, causing frequent pipe leaks and breaks. To better understand the failure mechanism of CI pipes, this paper provides an efficient numerical approach to analyse the behaviour of CI pipes under various loading conditions. The numerical investigation was realised by implementing a hyperbolic constitutive model (a simplified nonlinear stress-strain analysis) for CI materials into finite element analysis (FEA) in ABAQUS. Three-dimensional (3-D) FEAs were carried out for a series of uniaxial tensile and compressive tests, 3-point beam bending tests and ring bending tests on various CI pipe coupons. The stress-strain characteristics and load-deflection responses obtained from these numerical examples were validated by experimental results. The numerical results obtained from the proposed method are in good agreement with the measured data, which indicates that the mechanical performance of deteriorated CI pipes can be adequately modelled using the relatively simple nonlinear constitutive model implemented in 3-D FEA. As nonlinear behaviour has proven to be intrinsic to the widely used CI pipes, it is expected that the proposed 3-D FEA modelling technique will be of importance to the evaluation of the mechanical performance of CI pipes and, possibly, other CI structures.

In the context of the recently developed breakage mechanics that is based on thermodynamics principles, this paper presents a mathematical modelling procedure to implement the simple (i.e., linear elastoplastic) breakage constitutive model using finite element analysis (FEA) with illustrations by engineering applications. More informative mathematical derivation procedures of energy dissipations, plastic potential, yield function and non-associated flow rules are presented. In contrast, the existing relevant publications often lack sufficient elaboration, leaving knowledge gaps in the full understanding the model. This is followed by a series of numerical simulations in ABAQUS to test the model at the constitutive level. Various isotropic and triaxial shear tests in drained or undrained conditions are tested to illustrate the key features of the breakage model, which seem to be overlooked in the literature. Finally, a few numerical results are compared with experimental shear tests to demonstrate the ability of the simple breakage model in reflecting mechanical responses of crushable granular aggregates.

Failure of cast iron water mains in Australia is a common occurrence. Water utilities are seeking solutions to optimise the renewal and rehabilitation of ageing cast iron critical water mains (diameter ≥ 300 mm). Failure pressures of three large-diameter cast iron pipe specimens (600 mm in diameter) were tested. A large corrosion patch was machined onto each pipe section to initiate pipe failure. A large corrosion patch and significant reduction (>90%) of pipe wall thickness were needed to fail the tested pipe specimens. All three pipes under test exhibited leaking before bursting, indicating that the concept of leak-before-break (LBB) could be used for pipe failure prevention. In addition, LBB provides valuable information that could be added to the pipe asset database to make better management decisions on repair or replacement along with all other asset information. The study also found that small corrosion patches (

Cast iron was the dominant material for buried pipes for water networks prior to the 1970s in Australia and overseas. At present, many water utilities still have a significant amount of ageing cast iron pipes. Cast iron is a brittle material and when large diameter cast iron pipes (diameters above 300 mm) further deteriorate, the consequences of failure can be substantial. Focusing on the likelihood of failure to assist risk assessment, this paper examines the performance of large-diameter cast iron pipes using probabilistic analysis, incorporating uncertainties of governing variables. Finite element analysis is first conducted to study the physical mechanism of buried pipes subjected to complex environmental conditions. The deterioration of cast iron pipes due to corrosion is considered on the basis of recent research. The uncertainties of governing variables, such as the physical properties of soil, cast iron, water pressure and corrosion patterns, in pipe failure risk assessment are considered. Using probabilistic physical modelling, the lifetime probability of failure is derived and a time-dependent sensitivity analysis is presented. The results of this probabilistic physical modelling are compared with cohorts of failure data from two Australian water utilities to examine the underlying trends from both physical modelling and statistical analysis.

Tests of rock strength under different loading rates and stress paths often lead to ambiguous results, as both factors are inter-playing each other. As a result, there is surprisingly little research into the study of unifying both factors when comparing the rock strengths from various triaxial compression tests. In this technical note, we propose a simple but rigorous mathematics expression to assess and compare the rock strengths under different loading rates and stress paths. To make the proposed method as accessible as possible to a broad application, we have derived the explicit forms of solutions for three popular rock failure criteria. We then examine and validate the proposed method using the results of triaxial tests on marbles and sandstones, based on the important Mohr-Coulomb criterion.

This paper investigated shear-related roughness classification based on Fuzzy comprehensive evaluation, and established a new strength model of natural rock joint. The joint profiles were extracted from 3D data to evaluate roughness, and a series of direct shear tests were carried out on three kinds of natural rock joints. The height statistical parameters Sm, Sq, Ss and Sk, and the textural statistical parameters Si, Sc, and Z2 were measured by Talysurf morphology instrument. Considering the existence of strong positive relations between Sm and Sq, and Z2 and Si, the four morphological parameters of Si, Sq, Sc, and Sk are considered as the main influencing factors related with rock joint shear behaviors. A new fracture roughness coefficient FRC is proposed based on fuzzy comprehensive evaluation (FCE), which considers that the influence of multi morphology parameters on the roughness of rock joint surface, and generally, the FRC is higher than the JRC. Compared with the previously published shear strength models, the proposed FRC-JCS shear strength model, which can more comprehensively reflect the influence of joint surface morphology parameters to shear strength, are in better agreement with the experimental data.

The dynamic performance of a bridge-tunnel transition section with a deep buried pile-plank structure (DBPPS) for short transitions was studied. Field tests were performed, analyzing accelerations, velocities and displacements in the track and subgrade. Based on the field test results, the influences of the train types, driving direction and running speed on the dynamic response in the transition zone were investigated. A 3D finite element model considering vehicle-track-subgrade coupled interactions was presented, and the results from the model were compared with the measured responses. Based on the model, the distribution of the vertical dynamic stress in the subgrade was analyzed, and the running quality for the comfort of passengers on the train and the dynamic response along the DBPPS transition zone with alternative fillings in the subgrade, such as graded gravel and AB group filling (well graded coarse-grained soil with less than 30% fine-grained soil), were discussed. Comparatively, the graded gravel is recommended for the filling of base layer in the DBPPS subgrade.

The soil-concrete interface shear strength, although has been extensively studied, is still difficult to predict as a result of the dependence on many factors such as normal stresses, surface roughness, particle sizes, moisture contents, dilation angles of soils, etc. In this study, a well-known rigorous statistical learning approach, namely the least squares support vector machine (LS-SVM) realized in a ubiquitous spreadsheet platform is firstly used in estimating the soil-structure interface shear strength. Instead of studying the complicated mechanism, LS-SVM enables to explore the possible link between the fundamental factors and the interface shear strengths, via a sophisticated statistic approach. As a preliminary investigation, the authors study the expansive soils that are found extensively in most countries. To reduce the complexity, three major influential factors, e.g., initial moisture contents, initial dry densities and normal stresses of soils are taken into account in developing the LS-SVM models for the soil-concrete interface shear strengths. The predicted results by LS-SVM show reasonably good agreement with experimental data from direct shear tests.

Existing research on rock freeze-thaw mainly focuses on a single freeze-thaw process, while little attention is paid to the cumulative effect of cyclic freeze-thaw on rock mass joints. However, the accumulated freeze-thaw effects are precisely the leading cause of rock mass deterioration and damage in severe cold regions. This study aims to investigate the use of a novel laboratory testing method, i.e., membrane pressure sensors in the joint, to demonstrate the impact of cyclic frost-thaw on jointed rocks. With the sensors, the change of frost-heaving pressure in the joint under cyclic process is continuously monitored. The measurements indicate that under freeze-thaw cycles, the initiation of frost-heaving pressure is critical, which is followed by an explosion, stability, and ablation stages. In these stages, the maximum frost-heaving pressure is observed to emerge at the early stage of the freeze-thaw cycle. Based on the experimental observations, frost-heaving pressure evolution law and damage mechanism of jointed rock masses are analyzed. For example, the peak frost-heaving pressure increases exponentially with the decrease of temperature and decreases exponentially with the increase of freeze-thaw cycles. Also, the pressure has a positive linear relationship with the geometric size of the joint. In essence, the deterioration of freeze-thaw cycles on jointed rock masses is mainly due to crack propagation caused by the frost-heaving pressure.

At present, a significant proportion of Australia’s ageing water infrastructure is composed of cast-iron pipes. The corrosion of cast-iron pipes is the main triggering factor for Australia’s water industry. It has been found that the failure mode of small diameter water mains (

Concentrated working stress of a corrosion pit is known to be an important factor inducing the deterioration and consequently the breakage of a buried pipe. In this paper, we investigate the stress concentration factors (SCFs) of isolated elliptical corrosion pits using 3-D finite element analyses. The elliptical pits are fully characterized by their 3-D geometries, i.e., major and minor diameters and pit depth via a series of parametric studies of finite element pipe models. This is to quantify the effect of geometric variations of the pits on SCF. Realizing the fact that the 3-D finite element analysis is computationally intensive, efficient statistically predictive models have been developed based on least squares support vector machine (LS-SVM) realized in a ubiquitous spreadsheet platform. This approach shows very close predictions of SCF to the numerical findings for elliptical corrosion patterns on buried pipes. Particularly, two typical kernel functions have been adopted to cross validate the excellent performance of the LS-SVM method in SCF prediction of corroded pipes.

The stability evaluation of earth slopes is a common practice in geotechnical designs. To account for uncertain characteristics of soil properties, probabilistic evaluation that requires repeated calculations of factor of safety (FoS) is inevitably encountered. Because FoS for most slopes in practice is computed numerically due to the lack of analytical solutions, various surrogate models are usually developed to ease the probabilistic evaluation. This paper investigates the probability of slope system failure with surrogate models based on the least-squares support vector machine (LS-SVM) regression. First, some limitations in the current application of LS-SVM to complex slopes with multiple failure modes are pointed out. In the context of Monte Carlo simulations (MCS) for probabilistic slope stability evaluation, the authors first discuss the importance of space filling of training data to the success of the LS-SVM and then propose an efficient routine for generating the training data by which the global prediction of FoS is reasonably guaranteed. The application of the LS-SVM is illustrated through two well-documented slope examples. Comparative studies are conducted to identify the effect of training data size and hyperparameters on the model performance. It is observed from this study that the LS-SVM model can reasonably capture the global characteristics of complex slopes only when all the relevant soil layers are treated probabilistically; otherwise, some local inconsistency could be encountered. Focusing on the probability of failure prediction defined by different FoS thresholds, it is shown that the LS-SVM is robust and a promising method for the evaluation of complex slopes.

This letter extends an earlier theoretical and numerical analysis that aimed to improve predictions for the large-displacement end-bearing capacity of piles in sand by considering the boundary conditions applying to steady penetration and the effects of grain crushing via breakage mechanics. The earlier work led to good agreement with the end-bearing capacities, soil displacements and evolution of grain size distributions observed in experiments of penetrating model piles. The purpose of the current paper is to complement the previous evaluation through comparisons with more recently published calibration chamber measurements of the stresses surrounding instrumented model piles penetrating into dense silica sand. Encouraging agreement is demonstrated for the radial, circumferential and vertical stress components. Scope for further improvements is also identified.

A new formula is proposed for the end-bearing capacity of piles penetrating into crushable soils. The formula is based on a breakage mechanics model that accounts for the evolution of the grain size distribution (GSD) due to grain crushing with only physically meaningful parameters. The model is integrated using the finite-element method to study the penetration problem. Predictions of GSDs surrounding piles and pile end-bearing capacities are validated against experiments. Next, a parametric study is carried out to quantify the effects of grain crushing on the bearing capacity, and then to establish the formula. The predictive capability of the new formula is highlighted against predictions by previous formulae, which highlights its superior origins.

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...