Guosheng Jiang

Vertical dynamic response of pile embedded in layered transversely isotropic soil

The dynamic response of pile embedded in layered transversely isotropic soil and subjected to arbitrary vertical harmonic force is investigated. Based on the viscoelastic constitutive relations for a transversely isotropic medium, the dynamic governing equation of the transversely isotropic soil is obtained in cylindrical coordinates. By introducing the fictitious soil pile model and the distributed Voigt model, the governing equations of soil-pile system are also derived. Firstly, the vertical response of the soil layer is solved by using the Laplace transform technique and the separation of variables technique. Secondly, the analytical solution of velocity response in the frequency domain and its corresponding semianalytical solution of velocity response in the time domain are derived by means of inverse Fourier transform and convolution theorem. Finally, based on the obtained solutions, a parametric study has been conducted to investigate the influence of the soil anisotropy on the vertical dynamic response of pile. It can be seen that the influence of the shear modulus of soil in the vertical plane on the dynamic response of pile is more notable than the influence of the shear modulus of soil in the horizontal plane on the dynamic response of pile.

Vertical dynamic impedance of tapered pile considering compacting effect

Based on complex stiffness transfer model, the vertical vibration of tapered pile embedded in layered soil is theoretically investigated by considering the compacting effect of the soil layer surrounding the tapered pile in the piling process. Allowing for the stratification of the surrounding soil and variable crosssection of the tapered pile, the pile-soil system is discretized into finite segments. By virtue of the complex stiffness transfer model to simulate the compacting effect, the complex stiffness of different soil segments surrounding the tapered pile is obtained. Then, substituting the complex stiffness into the vertical dynamic governing equation of tapered pile, the analytical solution of vertical dynamic impedance of tapered pile under vertical exciting force is derived by means of the Laplace technique and impedance function transfer method. Based on the presented solutions, the influence of compacting effect of surrounding soil on vertical dynamic impedance at the pile head is investigated within the low frequency range concerned in the design of dynamic foundation.

Torsional Dynamic Impedance of a Tapered Pile Considering its Construction Disturbance Effect

The dynamic response of a tapered pile (considering its construction disturbance effect) is investigated when the tapered pile is subjected to a time-harmonic torsional loading. For most engineering conditions, the surrounding soil may be weakened or strengthened owing to the construction disturbance effect of the tapered pile, resulting in the soil becoming radially inhomogeneous. In order to consider this problem, the circumferential shear complex stiffness transfer model is proposed to simulate the radial inhomogeneity of soil. Then, the governing equations of a tapered pile-soil system subjected to torsional dynamic loading are established. By virtue of the circumferential shear complex stiffness transfer method and the impedance function transfer method, the analytical solution of torsional dynamic impedance at the head of the tapered pile is derived. Based on the presented solution, the influence of the construction disturbance effect of the surrounding soil on the torsional dynamic impedance at the pile head is investigated within the low-frequency range concerned in the design of a dynamic foundation. The results show that, even if the hardening range and softening range of the surrounding soil vary within a smaller scale, the hardening effect and softening effect also have a notable influence on the torsional dynamic impedance at the pile head.

Effects of High Temperature on the Mechanical Properties of Chinese Marble

With the increasing tendency of rock engineering applications to involve high temperatures, such as deep geological disposal of nuclear waste (Salama et al. 2015; Verma et al. 2015; Ye et al. 2016) and exploitation of geothermal resources (Sigurvinssona et al. 2007; Gelet et al. 2013; Zeng et al. 2013), research on the mechanical properties of rocks under/after exposure to high temperature has again attracted great attention. The rock material, a typical porous medium, contains original micro-holes and micro-cracks. Under hightemperature conditions, mineral thermal expansion and reactions occur in a rock, leading to variations in rock physical and mineralogical characteristics (Tian et al. 2012, 2013; Ozguven and Ozcelik 2014), and causing extension of the primary micro-cracks and development of new ones inside the rock body (Ferrero and Marini 2001). Consequently, the rock mechanical properties (e.g., elastic modulus and uniaxial compressive strength) exhibit macroscopic variation with temperature, which has been verified experimentally through measurements of rock samples both under and after exposure to high-temperature conditions (e.g., Ranjith et al. 2012; Brotóns et al. 2013; Yang et al. 2014; Zhang et al. 2016). Among the corresponding test results, extensive literature studies have been conducted on common igneous rocks such as granite (Heuze 1983; Dwivedi et al. 2008) and sedimentary rocks such as sandstone (Tian et al. 2012), providing interesting conclusions and guidance to scholars and engineers. Unfortunately, a similar literature study on metamorphic rocks has not been openly published in English. Marble is a widely distributed metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Its mechanical characteristics are mainly influenced by the original rock mineral composition and the environments experienced during metamorphic processes. In this study, an extensive review of Chinese publications, not considered in the English-speaking scientific community so far, covering the elastic modulus, uniaxial compressive strength, and peak strain of marble under/after exposure to high-temperature conditions and a generalized rule describing the effects of high temperature on marble are presented.