Construction Safety and Quality Supervision Station

Shanghai, China

Construction Safety and Quality Supervision Station

Shanghai, China

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Xiao W.,Tongji University | Xiao W.,Sichuan Agricultural University | Xia C.,Tongji University | Wang W.,Construction Safety and Quality Supervision Station | And 2 more authors.
International Journal of Geomechanics | Year: 2016

A contact algorithm to determine the aperture evolution of a rock fracture during shearing is reported. The algorithm was based on a theoretical normal closure model and semianalytical dilation model and required only the three-dimensional topography data of the two fracture surfaces at the initial stage before shearing. It allowed the prediction of the aperture distribution of a fracture under normal stress and various shear displacements, which is difficult to observe in coupled shear-flow tests. To ensure the precision of the surface topography data, a laser-scanning profilometer system was used for surface topography measurement. The contact algorithm was then used to predict the aperture evolution of a marble fracture during shearing. The results of aperture variation under normal stress and shear displacement were analyzed and compared with an equivalent aperture derived from back-calculation of flow test results. The results indicated that the contact algorithm is efficient in predicting aperture evolution. © 2015 American Society of Civil Engineers.


Xia C.,Tongji University | Xiao W.,Tongji University | Wang W.,Construction Safety and Quality Supervision Station | Ding Z.,China Railway Eryuan Engineering Group Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2010

The mechanical and flow characteristics of rock joint are closely associated with its three-dimensional topography. For a single rock joint, the roughness and waviness of its surface is of paramount importance to flow; and the flow characteristics are related not only to the topography of a single joint surface, but also to the composite topography of the upper and lower joint surfaces. Different contact condition results in different composite topography. The analysis of joint composite topography is the basis of research on flow in a single rock joint. In order to compute the three-dimensional composite topography effectively, the conditions for determining stable contact of two joint surfaces are presented; and the contact algorithm based on determinant conditions is introduced. The Visual C++ programming language is adopted to provide a procedure for three-dimensional composite topography calculation. By using the procedure, the composite topography of joint under different contact conditions can be calculated conveniently with the surface topography data derived from TJXW-3D portable rock surface topography laser scanner developed by Tongji University. Then the fresh marble tension joint is taken as an object; and different contact conditions are formed by dislocating the upper joint surface from the lower joint surface for 1, 2, 3, 4, 5 mm respectively after scanning the joint surfaces by TJXW-3D topography scanner. Based on topography data, the composite topography parameters under different contact conditions are calculated by the procedure proposed above; and the influence of different contact conditions on joint composite topography is discussed, which provides a foundation for researches on the relations between three-dimensional composite topography and the mechanical and flow properties of joint under different contact conditions.


Xiao W.,Tongji University | Xia C.,Tongji University | Wang W.,Construction Safety and Quality Supervision Station
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2011

Joints are the main passages for underground water flowing through rock-masses. Fluid flow through joint has been one of research focuses on joint hydraulic properties. Due to the joint surface is rough and uneven, flow through a rough joint is greatly different from that between a pair of parallel plates. A void model for fluid flow through a rough rock joint is established. The joint plane is divided into a series of square meshes with the dimension of 1mm×1mm, the apertures of the grids of each mesh are determined by the 3D void composite topography. Assumed that the cubic law is applicable for fluid flow analysis in each mesh, analyse are performed one mesh by one mesh. Fluid flow through the whole joint plane is calculated by considering the continuity equation among the meshes and a procedure for flow calculation was compiled by MATLAB functions. Then an artificial marble tensile fracture is taken as an object, different contact states are formed by offsetting the upper joint surface along the length direction from the lower one for 1, 2, 3, 4, 5 and 6 mm respectively. The 3D void composite topographies in these six cases are calculated by contact algorithm, thus obtaining joint aperture distributions and the mean apertures under different contact states. The theoretical volumetric flow rates under different contact states calculated by void model and cubic law are compared with the results of laboratory flow tests carried out on the marble joint specimen. It indicated from the comparison that the results of void model are closer to experimental results than that resulting from cubic law and there existed a difference between void model and experimental results. And the reasons resulting in the difference were discussed.


Xiao W.,Tongji University | Xia C.,Tongji University | Wang W.,Construction Safety and Quality Supervision Station | Bian Y.,Tongji University
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2011

Uneven distribution of joint apertures mainly causes the tortuosity of flow through a rough joint. Taking two joint specimens B01 and B02 as research objects, laboratory flow tests and numerical simulations through the specimens are performed after scanning three-dimensional (3D) surface topography of joint. The tortuous streamlines of flow through a joint are derived from numerical simulations; and the tortuosity coefficient which quantitatively describes the tortuosity effect of flow through a joint is defined and calculated according to the 3D void composite topography. Then based on modified cubic law taking into account the roughness of joint surface, the new equation accounting for tortuosity effect for calculating flow volumetric rate through a joint is deduced by applying the equivalent channel model which is adopted to analyze the permeability of rock. The two constants A and B in the new equation are obtained by fitting the numerical simulation results of joint specimen B01. Then the flow rates of joint specimen B02 derived from the new equation and numerical simulations are compared with each other to validate the new equation. Furthermore, the flow volumetric rates of the two joint specimens derived from the new equation, SU Baoyu empirical method and laboratory flow experiments are compared with each other, which shows that the results obtained by the new equation agree well with experimental observations, while the SU Baoyu empirical method overestimates the flow rates, thus verifying the validity of the new equation.


Xiao W.,Tongji University | Xiao W.,Southwest Jiaotong University | Xia C.,Tongji University | Wei W.,Construction Safety and Quality Supervision Station | Bian Y.,Tongji University
Journal of Geophysics and Engineering | Year: 2013

Fluid flow through rock joints is greatly influenced by tortuosity and surface roughness, which cause a deviation from the cubic law of joint permeability. In this paper, in order to consider the combined effects of tortuosity and surface roughness on flow rate through a rough joint, a semi-empirical equation is first presented. In this equation, the impacts of tortuosity and surface roughness are represented by three quantitative parameters i.e., the tortuosity τ, surface tortuosity coefficient T s and relative roughness Δ/2d, all of which can be computed based on surface topography data. Furthermore, the empirical constant A in the equation is determined according to the results of flow tests on three artificial joint specimens. Then the validity of the semi-empirical equation is confirmed by use of previously published experimental and numerical results. The obtained semi-empirical equation can predict the fluid flow rates through a rough joint well, and will be helpful to investigate the permeability of rock masses. © 2013 Sinopec Geophysical Research Institute.


Xia C.,Tongji University | Xia C.,Shaoxing University | Gui Y.,Tongji University | Wang W.,Construction Safety and Quality Supervision Station | And 2 more authors.
Journal of Geophysics and Engineering | Year: 2014

To determine the void spaces of rock joints under different normal stresses and shear displacements, we mainly introduce a numerical method which was developed based on equivalent void space derived from composite topography. The new method requires the 3D surface data of rock joints, and the normal closure data of the compression test under different shear displacements, while in conventional methods, some disparate materials are inserted between the joint surfaces or special equipments are needed for the measurement of the void space of rock joints without shearing occurs. To apply the technique, a modified 3D box counting method that considers the self-affine fractal property of void spaces was employed to calculate the 3D fractal dimension of the void space. Specially designed experiment was conducted on a cylindrical specimen of artificial joints to explore aperture distribution, and the correlations between void space characteristics, 3D fractal dimension and mean aperture, and normal stress under different shear displacements. The present study focuses on the introduction of the new method for estimating void spaces of rock joints, while the void spaces model obtained contains the combined surfaces roughness and aperture information of rock joints under different normal loads and shear displacements is promising in investigating the mechanical and hydraulic properties during the loading process. © 2014 Sinopec Geophysical Research Institute.


Xiao W.-M.,Tongji University | Xia C.-C.,Tongji University | Wang W.,Construction Safety and Quality Supervision Station | Bian Y.-W.,Tongji University
Yantu Lixue/Rock and Soil Mechanics | Year: 2013

The contact area will make flow tortuosity more obvious and influence the flow rate significantly. In order to investigate the effect of contact area on fluid flow through joint, a conceptual flow model is established to obtain the contact influential coefficient. And the influential coefficient is introduced into the equation for flow rate calculation considering the effect of tortuosity; a new equation considering the effect of contact area is derived. As the contact area makes the calculation of tortuosity coefficient more complicated, an algorithm for calculating the average tortuosity coefficient is proposed based on the joint aperture distribution. An artificial marble joint is taken as an object and the surface topography data are scanned. In one hand, flow tests are carried out on the joint specimen under five levels of normal stresses. In the other hand, on the basis of the average tortuosity coefficients and contact area ratios of joint specimen under five levels of normal stresses calculated according to the joint surface topography data, the volumetric flow rates through joint specimen are predicted by the new equation considering contact area presented in this paper and Zimmerman's equation, respectively. Then the predictions of the two equations are compared with experimental observations. It is shown from the comparison results that the predictions of the new equation agree well with experimental observations, while Zimmerman's equation overestimates the flow rate through the joint, thus validating the veracity of the new equation.


Xiao W.,Tongji University | Xiao W.,Southwest Jiaotong University | Xia C.,Tongji University | Wang W.,Construction Safety and Quality Supervision Station | Bian Y.,Tongji University
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

In order to investigate fluid flow through a rough joint during shearing, shear dilation of a rough joint is firstly analyzed by using the shear dilation model developed by Barton, and then dilations under different shear displacements can be calculated. The Brown-Scholz (B-S) theoretical model is employed to compute the closures of joint under different levels of normal stress. The relation of the aperture during shearing with normal stress and shear displacement are established according to the relations among initial aperture, normal closure and shear dilation, on the basis of which a new equation accounting for the volumetric rates through a rough joint during shearing is derived. Then laboratory flow tests on rock joint specimens are carried out; and the new equation derived from the shear dilation model developed by Barton and Barton's empirical equation are adopted to predict flow rates through joint specimens. Comparisons between theoretical predictions and experimental results are conducted. From the comparisons, it is shown that predictions of the new equation agree well with experimental results while the results of Barton's empirical equation deviate from experimental results to a large extent, which verifies the validity of the new equation for predicting fluid flow through a rough joint during shearing.

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