This paper presents a simplified analytical approach for evaluating the load-displacement response of single tapered pile and pile groups under static axial compressive loads. The response of the tapered pile shaft is considered elastically in the initial stage, whereas the increase in stresses due to slippage along the pile-soil interface is obtained from a developed undrained cylindrical cavity expansion solution based on the K₀-based anisotropic modified Cam-clay (K₀-AMCC) model. An effective iterative computer program is developed to calculate the load-displacement behaviour of a single tapered pile. Regarding the response analysis of tapered pile groups, a finite-difference method is employed to calculate the interaction between tapered pile shaft, and the linear elastic model to simulate the interaction developed at the pile base. A reduction coefficient is introduced into the analysis of pile shaft interaction to clarify the reinforcing effect between tapered piles. Therefore, the settlement calculation methods of pile groups are proposed for different pile cap stiffness. The calculation methods of single tapered pile and pile groups are validated using two 3D Finite Element (FE) programs, and the comparison results show that reasonable predictions can be made using the method proposed in this paper. Parametric studies are conducted to investigate the effects of taper angle, soil anisotropy, pile spacing, and pile number on the load-displacement behaviour of single tapered pile and tapered pile groups.

This paper summarizes the results of small-scale laboratory modelling of pile behavior under lateral loading, considering the parameters such as short or long, single or group, spacing and rigidity or flexibility of piles. The head of piles was fixedly connected to the cap. In addition, the PIV method has been used to examine the effect of the mentioned parameters on the failure mechanism and pile-soil interaction more accurately. The results show that the short piles have a rigid movement, the displacement of the surrounding soil has occurred along the total length of the pile and the piles rotate around a point but the long piles have a flexible movement at the part of the pile length. It seems that the group effect be more obvious for long piles than short piles. Also, the effective depth of total soil displacement vectors around the trail pile is more than the lead one in long pile group, while this depth for trail pile is less than the lead pile in short pile group. Due to the sharper angles of total displacement vectors around the trail pile, the intensity of soil shear strains around the trail pile is greater than the lead pile.

Although the development and utilization of X-section cast-in-place concrete (XCC) pile have been reported for some time, the long-term effects of XCC piling in fine-grained soil, in particular the set-up effects, have received little attention. This paper reports a coupled effective analysis of XCC piling using the dual-stage Eulerian-Lagrangian (DSEL) technique. The pile installation and subsequent soil consolidation was explicitly and consecutively modelled. The generation of excess pore pressure and alteration of stress states during the pile installation were explored. The distribution and magnitude of effective normal stress at pile/soil interface, in particular its evolution with time, were investigated. The influence of set-up effects on the XCC pile shaft resistance was assessed and quantified. It was found out, although the shaft resistances of both XCC and circular pile develops substantially with time, the consolidation in the wake of XCC pile installation can bring in more capacity enhancements and therefore practical benefits. The ultimate shaft resistance of XCC pile is 45% higher than that of the circular pile of the same cross-sectional area. Additionally, practical advice was given on how to optimize of the cross-sectional shape of XCC piles to take full advantage of set-up effects and achieve economical designs.

In this study, a rock tunnel subjected to blast load is modeled mathematically. For this purpose, a cylindrical shell element is used and the motion equations are derived by energy method and Hamilton's principle. In the inner surface of tunnel, different blast holes are considered and its force in radial direction is coupled by motion equations. The structural damping of the structure is assumed by Kelvin-Voigt model. Hoek-Brown failure criterion is utilized for explosion damage analysis of the tunnel. The motion equations are solved numerically by differential quadrature method (DQM). The effect of different parameters such as depth of tunnel, number and diameter of blast holes, type of stone, geological strength index (GSI) and density of stone, type and mass of explosive material are studied on the damage factor of Hoek-Brown criterion. Numerical results show that with increasing the density of explosive material, number and diameter of blast holes, the thickness of damage is increased in the tunnel. In addition, the depth of damage is decreased with increasing strength, GSI, density of rock and depth of tunnel.

To determine ground stress behavior under the special condition of a regenerated roof, we established a model of elastic rectangular cantilever thin plates. Moreover, the critical conditions for bending and fracturing the regenerated roof during mining were analysed. Meanwhile, by applying continua FLAC-3D numerical simulation, this research simulated changes in the stress and strain on a regenerated roof during mining and proposed prevention and control methods for dynamic disasters. The results show that: (1) the thinner the regenerated roof, the larger the tensile stress on the roof based on analysis using the theoretical model. Furthermore, the longer the advance distance during mining, the greater the tensile stress on the regenerated roof. (2) By analysing simulation results, during the fracturing of the regenerated roof, roof displacement firstly suddenly increases and then gradually decreases to be stable. Floor-heave-induced displacement presents a divergent state, that is, increases outwards in an elliptical manner. (3) For control of the regenerated roof, monitoring on activities of the roof should be strengthened and stress should be relieved timeously. Moreover, effective support methods should be taken to prevent development of hazards on working faces and roadways caused by the widespread behavior of the roof.

The reliability of reinforced concrete structures is frequently compromised by the deterioration caused by reinforcement corrosion. Evaluating the effect caused by reinforcement corrosion on structural behaviour of corrosion damaged concrete structures is essential for effective and reliable infrastructure management. In lifecycle management of corrosion affected reinforced concrete structures, it is difficult to correctly assess the lifecycle performance due to the uncertainties associated with structural resistance deterioration. This paper presents a stochastic deterioration modelling approach to evaluate the performance deterioration of corroded concrete structures during their service life. The flexural strength deterioration is analytically predicted on the basis of bond strength evolution caused by reinforcement corrosion, which is examined by the experimental and field data available. An assessment criterion is defined to evaluate the flexural strength deterioration for the time-dependent reliability analysis. The results from the worked examples show that the proposed approach is capable of evaluating the structural reliability of corrosion damaged concrete structures.

With the development of city construction, the situations of foundation pit excavations adjacent to an existing structure occur more frequently. A series of centrifuge model tests and numerical analyses considering actual excavation process were performed to study the deformation and earth pressure of retaining wall, deformation characteristics of retained soil with various limited soil widths. The horizontal displacement and bending moment of the retaining wall decrease with decreasing limited soil width while the rate of the decrease increases with decreasing limited soil width. The horizontal displacement of the retained soil decreases with decreasing limited soil width while the settlement of the retained soil increases with increasing limited soil width. The deformation zone is almost triangular for unlimited condition and trapezoidal for limited condition. As the limited soil width decreases, the deformation zone shrinks and the inclination of deformation zone increases. The lateral earth pressure on the retaining wall shows two-segment distribution and decreases with decreasing limited soil width. The vertical earth pressure shows non-uniform distribution along width and decreases with decreasing limited soil width due to increasing arching effect. The critical width is much smaller than excavation influence width. This may be explained by the fact that only the deformation of soil within critical width will influence the soil near the wall.

This research presents dynamic response analysis of a porous functionally graded (FG) nanobeam under a moving point load. The nanobeam formulation has been established with the use of a higher-order refined beam model and nonlocal strain gradient theory (NSGT) including two scale factors named nonlocal and strain gradient factors. The porous FG material has been modeled via modified power-law functions which contain porosity volume according to even or uneven porosity dispersions. Moreover, graded nonlocality has been considered in order to provide a better modeling of size effects for FG nano-size structures. The governing equations of the nanobeam have been discretized with the use of differential quadrature method (DQM) and inverse Laplace transform approach has been utilized to calculate the dynamic deflections. The main findings of the present research indicate the influences of nonlocal strain gradient factors, moving load speed, pore amount, porosity distribution and elastic medium on dynamic deflection of FG nanobeams.