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Xu S.-L.,Hefei University of Technology | Liu Y.-G.,Hefei University of Technology | Xi D.-Y.,Hefei University of Technology | Li G.-C.,Zhejiang East China Engineering Safety Technology Co. | Du Y.,Hefei University of Technology
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

The stress state and the geometrical structures in rock mass are adjusted during unloading. Since it is difficult to describe the process of stress adjustment, the geometrical structures are used in the present paper to investigate the process of rock mass unloading, and the elastic wave velocity is studied by considering the interaction of geometrical structure and elastic wave. A double-crack structure is employed to make approximate analysis of the elastic wave velocity in jointed rock mass. In the model, the analysis method of interaction within the double-crack structure is used to partly consider multiple scattering between the joints of rock mass, and the linear superposition method between double-crack structures is adopted to analyze the localization effect for defects in rocks. The influence of unloading on the rock bridge is described by the opening displacement and the opening rate of joints, and variation of elastic wave velocity of four different kinds of rocks corresponding to two dominant frequencies, 25 kHz and 1 kHz, is studied under excavation unloading condition. The results show that in the process of unloading, relative acoustic velocity corresponding to 25 kHz and seismic velocity corresponding to 1 kHz are gradually decreased; however, the decreasing degree of acoustic velocity is less than that of seismic velocity. For example, acoustic velocity of highly unloaded rock mass reduces to be 80% of that of the original rock mass, and seismic wave velocity reduces to be 50% of that of the original rock mass. These conclusions are of good guidance for the inspection and evaluation of water conservancy project and railway tunneling construction. Source


Di S.,Hydrochina Huadong Engineering Corporation | Di S.,Zhejiang University | Shan Z.,Hydrochina Huadong Engineering Corporation | Wang M.,Hydrochina Huadong Engineering Corporation | And 3 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

Test methods which are suitable for testing shear wave velocity in the offshore site and intertidal zone are studied and compared. The shear wave velocity in-situ test for the Xiaoyangkou intertidal zone of Yellow Sea is conducted. The statistical relationships between change law of shear wave velocity and soil parameters are analyzed and the shear wave velocity is predicted by the built relationships. In addition, some applications of test data are analyzed. The research results show that: (1) The suspension test method for shear wave velocity is appropriate in the study site by the comparison of economic applicability. (2) There exist power function relationships between the shear wave velocity and the depth of test data and they have a good relativity. In the meantime, according to statistical relationship analysis of soil layers, the correlations and envelope curves basically reflect their regularity. (3) The relationships between shear wave velocity and soil parameters are power or linear functions, and they correlated well. (4) Based on the test data, compound relationships are established among shear wave velocity Vs, void ratio e, density ρ and effective gravity stress σ'. Based on the methods, good function results can be achieved through the contrast analysis of the calculation results; and other prediction analysis for relative parameters can also be performed. (5) Furthermore, based on the in-situ test data, soil type classification, dynamic parameters calculation and earthquake liquefaction judgments are carried out. The methods and results can provide references for survey and design engineers. Source


Xu S.-L.,Hefei University of Technology | Zheng W.,Hefei University of Technology | Liu Y.-G.,Hefei University of Technology | Xi D.-Y.,Hefei University of Technology | Li G.-C.,Zhejiang East China Engineering Safety Technology Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

The propagation rules of elastic wave in rock mass with defects take on scale effect, just like the rock mass. The dynamic finite element method (DFEM) is employed to investigate the propagation rules of elastic waves at site-EC37-201-06. The whole computation area is 3.0×3.2 m2 and 15 kinds of computation scales are applied. A static finite element method (FEM) is used to study the relations of elastic wave velocities to the confined pressure and computation scales at site-EC37-101-06. The whole computation area is 1.2×1.2 m2 and 60 kinds of computation scales are applied. The ray theory is used in the former method, and the effective media theory is used in the later. The scale effect of elastic waves is obtained, but there are differences for the two methods. To establish their relations and provide a simple model for engineering computation, a semi-theoretical phase velocity equation is proposed based on the dimensionless method. Compared with the in-situ sonic velocities, seismic velocities and velocities computed by the theoretical model with randomly distributed joints, the proposed equation can be well used in rock mass. Source


Liu Y.,Anhui University of Science and Technology | Xu S.,Anhui University of Science and Technology | Xi D.,Anhui University of Science and Technology | Li G.,Zhejiang East China Engineering Safety Technology Co. | And 2 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2010

The jointed basalt is a kind of complicated material with large numbers of complex structures such as micro-cracks, micro-holes at the meso scale, and with non-uniformity and non-continuity properties at the macro scale, which leads to complexity of propagation rules of elastic wave in them. The analytical method based on the continuity can not be used to fully deal with those. In the present paper, for the study of mesostructure of rock on the law of wave propagation, cracks are taken for example and treated as inner boundaries. Based on the Green's function method, considering the introduction of suitable inner boundary conditions, and combined with method of boundary integral, the scattering of elastic wave is studied. Wave velocities of elastic wave predicted by the dispersion equation are compared to the results of laboratory experimental and in-situ test results, which show that the theoretical results in the present model are consistent well with in-situ test results; however, there is a wide gap with the results of laboratory experiment, which may be due to the differences between the environment of indoor experiment and in-situ test such as the stress state of rock samples, temperature and other factors. Furthermore, the mesostructures factors of the jointed basalt influencing on the dispersion effect are discussed, which results that the dispersion effect is strengthened with the increase in porosity and crack length in a certain range; all those results are guidance for in-situ test of acoustic and seismic wave. Source

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