Zheng H.,Beijing University of Technology |
Liu Z.,CAS Wuhan Institute of Rock and Soil Mechanics |
Ge X.,CAS Wuhan Institute of Rock and Soil Mechanics
International Journal for Numerical Methods in Engineering | Year: 2013
For second-order problems, where the behavior is described by second-order partial differential equations, the numerical manifold method (NMM) has gained great success. Because of difficulties in the construction of the H 2-regular Lagrangian partition of unity subordinate to the finite element cover; however, few applications of the NMM have been found to fourth-order problems such as Kirchhoff's thin plate problems. Parallel to the finite element methods, this study constructs the numerical manifold space of the Hermitian form to solve fourth-order problems. From the minimum potential principle, meanwhile, the mixed primal formulation and the penalized formulation fitted to the NMM for Kirchhoff's thin plate problems are derived. The typical examples indicate that by the proposed procedures, even those earliest developed elements in the finite element history, such as Zienkiewicz's plate element, regain their vigor. © 2013 John Wiley & Sons, Ltd.
Huang L.-X.,CAS Wuhan Institute of Rock and Soil Mechanics
Yantu Lixue/Rock and Soil Mechanics | Year: 2011
In rock dynamics, one of typical types of loading is impact loading, which can induce the strain rate up to 1 × 10 -1-1 × 10 4 s -1. Impact loading can be generated by a dynamic machine, Hopkinson bar testing equipment and blasting, and is used to investigate the dynamic behavior of rock. When rock is subjected to dynamical loading, inertial effect will become significant. Hence the objective of rock dynamics is to investigate the propagation and dissipation of stress waves in rock, the interaction between the stress waves and the joints of rocks, the reflection, diffraction and injection of the stress waves in layered materials. Initial study of rock dynamics in China could be traced back to the early sixties of last century, when the dynamic effect of blasting on the slope stability of Daye Iron Mine was investigated. Comprehensive research for such a subject started in 1965, when State Commission of Science & Technology and National Defense Commission of Science & Technology approved to establish the defense engineering research group, and launched "construction and research for protective engineering" as a key national research program. Through such events, China built up the foundation for its rock dynamics study. In 1987, the Commission of Rock Dynamics, a sub-committee of Chinese Society of Rock Mechanics and Engineering was founded; and this event became the milestone of the further development of rock dynamics. Members of the commission came from universities and research institutions of water conservancy, hydropower, energy, mining, coal, petroleum, railway transportation etc. Organized by the commission, the "National Conference for Rock Dynamics" has been held every two years, making a great contribution to the advancement of rock dynamics research. This paper will introduce the development and new achievements of rock dynamics in China recent 10 years; and it can be divided into two parts, i.e. the past achievements and the future development trends.
Zheng H.,CAS Wuhan Institute of Rock and Soil Mechanics |
Li X.,CAS Wuhan Institute of Rock and Soil Mechanics
International Journal of Rock Mechanics and Mining Sciences | Year: 2015
In the classical Discontinuous Deformation Analysis (DDA) the contact conditions are enforced by what is referred to as open-close iteration. The open-close iteration involves repeatedly fixing and removing the artificial springs between blocks in contact and thus falls into the category of trial-and-error solution procedures that cannot guarantee the solution is always convergent. Meanwhile, improper stiffness parameters of the artificial springs might cause numerical problems. In order to avoid the introduction of the artificial parameters and to avoid the open-close iteration, this study reformulates DDA as a mixed linear complementarity problem (MLCP). Then, the Fisher-Burmeister Line Search Algorithm (FBLSA) is modified to solve MLCP. Some typical examples including those originally designed by the DDA inventor are reanalyzed, proving the procedure is feasible. © 2015 Elsevier Ltd.
Zheng H.,Beijing University of Technology |
Xu D.,CAS Wuhan Institute of Rock and Soil Mechanics
International Journal for Numerical Methods in Engineering | Year: 2014
Aiming to solve, in a unified way, continuous and discontinuous problems in geotechnical engineering, the numerical manifold method introduces two covers, namely, the mathematical cover and the physical cover. In order to reach the goal, some issues in the simulation of crack propagation have to be solved, among which are the four issues to be treated in this study: (1) to reduce the rank deficiency induced by high degree polynomials as local approximation, a new variational principle is formulated, which suppresses the gradient-dependent DOFs; (2) to evaluate the integrals with singularity of 1/r, a new numerical quadrature scheme is developed, which is simpler but more efficient than the existing Duffy transformation; (3) to analyze kinked cracks, a sign convention for argument in the polar system at the crack tip is specified, which leads to more accurate results in a simpler way than the existing mapping technique; and (4) to demonstrate the mesh independency of numerical manifold method in handling strong singularity, a mesh deployment scheme is advised, which can reproduce all singular locations of the crack with regard to the mesh. Corresponding to the four issues, typical examples are given to demonstrate the effectiveness of the proposed schemes. © 2014 John Wiley & Sons, Ltd.
Zheng H.,CAS Wuhan Institute of Rock and Soil Mechanics
Engineering Geology | Year: 2012
In the stability analysis of landslides based on limit equilibrium methods, the "rigorous" methods that satisfy complete equilibrium conditions are more reliable and are preferred. For two-dimensional analyses, the rigorous methods of slices are becoming mature in both theory and practice. However, the attempts to realize their three-dimensional rigorous counterparts have not yet been realized. Introducing the Morgenstern-Price (M-P) assumption on the internal forces of the slip body, this study presents the three-dimensional version of the M-P method, which is rigorous and applicable to failure surfaces of complex shape. In the formulation, meanwhile, the volume integrals over the slip body are transformed into the boundary integrals, rendering column-partitioning unnecessary. The methodology developed in this study can be utilized to extend those two-dimensional rigorous methods of slices to their three-dimensional rigorous versions. © 2012 Elsevier B.V.
Li J.C.,CAS Wuhan Institute of Rock and Soil Mechanics
Geophysical Journal International | Year: 2013
Studying wave propagation across joints is crucial in geophysics, mining and underground construction. Limited analyses are available for oblique incidence across non-linear joints. In this paper, the time-domain recursive method (TDRM) proposed by Li et al. is extended to analyse wave propagation across a set of non-linear joints. The Barton-Bandis model (B-B model) and the Coulomb-slip model are adopted to describe the non-linear normal and shear properties of the joints, respectively. With the displacement discontinuity model and the time shifting function, the wave propagation equation is established for incident longitudinal-(P-) or transverse-(S-)wave across the joints with arbitrary impinging angles. Comparison between the results from the TDRM and the existing methods is carried out for two specific cases to verify the derived wave propagation equation. The effects of some parameters, such as the incident angle, the joint spacing, the amplitude of incidence and the joint maximum allowable normal closure, on wave propagation are discussed. ©The Author 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.
Fan H.,Northwest University, China |
Kong L.,CAS Wuhan Institute of Rock and Soil Mechanics
Canadian Geotechnical Journal | Year: 2013
As indicated by the theory of a clay-water-electrolyte system, the dispersive mechanism of cohesive soil involves three aspects: low clay content, high sodium ion percentage, and strongly alkaline pH. Accordingly, an empirical equation was established with an associated procedure and criteria proposed for evaluating the dispersivity of cohesive soil. The equation consists of four soil physical and chemical indicators: liquid limit (WL), clay content (PC), sodium percentage in the pore water (PS), and pH. The equation is F = 4 - 0.01(2WL + PC - PS) + 0.1 pH, where F is the soil dispersivity value. Compared with the evaluation based on laboratory tests, the empirical equation had higher accuracy for the evaluation of the dispersivity of cohesive soil, and was thus conducive to greater engineering safety. This indicates that the proposed empirical equation is applicable for evaluating the dispersivity of cohesive soil in general engineering.
Li Z.,CAS Wuhan Institute of Rock and Soil Mechanics
Journal of Hazardous Materials | Year: 2014
Bioclogging of leachate drains is ubiquitous in landfills for municipal solid wastes. Formation of calcium precipitates and biofilms in pore space is the principal reason for clogging. But the calcium speciation in leachte rich in dissolved organic matters (DOM) remains to be uncovered. In spite of its complexity, NICA-Donnan model has been used to compute the speciation of metals and the binding capacities of humic substances. This study applies NICA-Donnan theory into the simulation of calcium speciation during the formation of precipitate-dominant clogging in leachate drainage aggregates for the first time. The consideration of DOC-Ca complexation gives reasonable explanation to the speciation of calcium, which is viewed as oversaturated, in leachate with concentrated DOM. The modeling results for calcium speciation are in good agreement with a large collection of experimental observations, suggesting that NICA-Donnan theory could be used in the modelings of reactive transport and clogging of landfill leachate collection systems. © 2014 Elsevier B.V.
She S.,CAS Wuhan Institute of Rock and Soil Mechanics |
Lin P.,Tsinghua University
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2014
According to the papers published in some relevant journals in the field of rock mechanics and geotechnical engineering in China, the representive papers published in recent years written by Chinese authors are analyzed. In association with China National Awards, "973 Program", "The Major Projects of National Science Foundation", and "TAN Tjongkie Lecture" etc., in the last decade, the challenging, development and relevant progress in rock engineering field are summarized. The major issues, key theories, engineering survey and design, rock excavation and reinforcement, and early warning and forecast in rock engineering are presented. Some typical rock engineering cases in China are also analyzed. Based on analysis of characteristics and associated problems in Chinese rock engineering developments, ten challenging issues in rock engineering are proposed subsequently; furthermore, some suggestions are given for adressing those problems.
Feng X.-T.,CAS Wuhan Institute of Rock and Soil Mechanics |
Hudson J.A.,Imperial College London
International Journal of Rock Mechanics and Mining Sciences | Year: 2010
Following two previous papers in which we discussed the ways ahead for rock engineering design methodologies, and presented two updated flow charts, this paper discusses how to establish the necessary quality and quantity of information required for rock engineering modelling and design. We demonstrate how different types of information are required by the different modelling and design methods, via their required inputs and constraints (a corollary being that a 'standard site investigation' is not appropriate) and that the degree of co-operation between the site investigation personnel and the modelling and design personnel is a crucial component. A five step procedure for establishing the required information is recommended. Two illustrative rock slope case examples (one 'simple', one 'complicated') demonstrate the different modelling methods used, the type of information that was obtained for the modelling and design, with the results and conclusions. The paper illustrates the importance of understanding and establishing the necessary information requirements and ensuring that this information is in fact obtainable and obtained. © 2009 Elsevier Ltd.