WU De-lun

Chongqing University of Technology

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XU Nian-chun

Chongqing University

Li Chengfang

Yang Le

Chinese Academy of Civil Aviation Science and Technology

Mingjie Zhao

University of Chinese Academy of Sciences

Ye Xiaoming

Lin Jun-zhi

Chongqing Jiaotong University

Jianhua Zhang

Wuhan University of Technology

Xiong Qidong

Cooperative Institutions

Chongqing University

Chongqing Jiaotong University

Chongqing University of Science and Technology

Chinese Academy of Civil Aviation Science and Technology

Yunnan Forestry Vocational and Technical College

China University of Mining and Technology

Daqing Oilfield General Hospital

Chang'an University

Air Force Institute of Aviation Medicine Affiliated Hospital

State Administration of Foreign Experts Affairs

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A WEIGHTED ABSORBING BOUNDARY CONDITION FOR THE WAVE PROPAGATION IN SATURATED POROELASTIC MEDIA

Chinese Journal of Geotechnical Engineering (1997)

WU De-lun Jianhua Zhang

An absorbing boundary condition is generally needed to model the wave propagation in an unbounded domain in finite element method analysis. Considering that the absorbing capability for the incident waves with large obliquity is commonly poor, a weighted absorbing boundary condition is presented and computational formulae are derived based on the Fourier transformation solution of wave propagation equations in the poroelastic media. Its efficiency is compared with the results of G. Degrande and G. De Roeck in a numerical example by a study of the reflected wave amplitudes for the waves - P1, P2 and SV at various angles of incidence. The results show that the weighted absorbing boundary is an improvement on the absorbing capability, especially for P1 and P2 waves.

Poromechanics

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Finite element analysis of underground caverns in layered rock mass based on Cosserat theory

Rock and Soil Mechanics (2010)

WU De-lun

When bilaminated rock mass is numerical analyzed by conventional finite element method,that the shortcomings produced is not only the huge modeling workload and maneuverability become more inefficient with layer numbers increasing;but also the method can't reflect the bending deformation of the layered material.The Cosserat medium expanded model is a equivalent methods aiming at the complex rock mass.The basic principle of the Cosserat continuum theory and its expanded constitutive model are introduced firstly;and the Mohr-Coulomb plastic yield criterion of the new model is given.Then the FEM program is written by using Matlab system;and it is applied to the underground caverns.The results of comparison between Cosserat model and conventional continuum model are presented;and it is shown that the program based on Matlab and Cosserat model is effective,applicable and superior.

Mohr–Coulomb theory

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Reflected Wave Isotraveling Time Circle and Its Application in Inverting Jointed Rock Masses

Journal of Chongqing Jianzhu University (2008)

XU Nian-chun Lin Jun-zhi WU De-lun

Joints are crucial factors in rock masses engineering,so using stress waves to invert joint attitude is a valuable practice.The stress wave emitted from a vibration source is reflected by joints and returns to the ground.A formula to calculate the reflected wave travel time was deduced using analytic geometry theory.In the formula,a direct relationship was established between a joint's real dip angle,real dip direction and the travel time at test spots on the ground.The reflected wave's isotravel time circle described by the formula has a clear conception and a definite meaning.Using the program on the MATLAB platform,this formula can be applied to invert the joint attitude by searching the center of the circle based on the measured travel time at the testing spots around the wave source.

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A poroelastic pressure research for nonsaturated clay

WU De-lun

In general, when dealing with issues on strength of clay, emphasis should be paid on the stress variation and the relative change in pore pressure. The unsaturated clay due to the existence of the solid, fluid and gas phases is much more complicated to deal with. In this paper applying the elastic deformation theory and theoretical gas law, and assuming the conversation of mass , a general pore pressure formula has been derived; as the result the Skempton formula抯 coefficients A and B are obtained. On other hand, applying the mixture theory the Bishop formula抯 coefficient X is obtained also. In parallel works, the experimental results have been presented to validate the academic theories. It shows that the capillary action has a little influence on pore coefficient.

Poromechanics

Effective stress

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A Cosserat Theory-based Numerical Simulation of an Underground Cavern in Layered Rock Mass

Journal of Chongqing Jianzhu University (2008)

Yang Le WU De-lun XU Nian-chun

Conventional equivalent continuum theory poorly interprets the bending deformations and damage phenomena encountered in rock engineering because the theory ignores the influence of gradient stress.The influence of the bending effect on deformation characteristics of the media has been considered in Cosserat continuum theory which introduces the concepts of coupled stress and bending curvature.The basic principle of Cosserat medium theory and its expanded constitutive model were introduced firstly.Next,a numerical simulation of an underground cavern was carried out using FLAC software.After this,the results of the Cosserat model and explicit joint model were compared.The simulation results not only displayed the bending deformation of layered rock mass well,but also demonstrated the validity and superiority of the Cosserat expanded model.

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Determination of suitable anchorhead spacing of prestressed anchor pile based on three-dimensional soil arching

Rock and Soil Mechanics (2011)

Li Chengfang Ye Xiaoming Xiong Qidong WU De-lun

The existing problem of load transmission path of traditional prestressed anchor piles is discussed;and a mechanical calculation model is first proposed based on three-dimensional soil arching effect by its mechanics property;and the correctness of the model is verified.Then the soil arch shape and arch rise are analyzed;and further the mathematical expression of the model is presented.Meanwhile,three-dimensional soil arch formation conditions are demonstrated;static equilibrium and the strength of the conditions are established.On this basis,anchorhead spacing control equation is deduced and the influences of shear strength parameters c and and soil pressure q on anchorhead spacing are analyzed.Finally,a project example is given so as to verify saving project cost.

Lateral earth pressure

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THE ULTRASONIC IDENTIFICATION OF ROCK MASS CLASSIFICATION AND ROCK MASS STRENGTH PREDICTION

Chinese journal of rock mechanics and engineering (2000)

Mingjie Zhao WU De-lun

Rock mass classification and rock strength predication are widely applied in rock engineering. In this paper several classifications have been developed for rock mass, e.g. the RMR and Q-system, and the Hoek-Brown criteria is the most accepted for rock mass strength predication. A combination of the RMR and Q-system is related to ultrasonic velocity based on the foregoing investigations and experience formulae, so that the rock mass classification can be assessed according to the measured ultrasonic velocity of rock mass in situ. Also by the existed relationship between the RMR and Hoek-Brown criteria, a prediction for the strength parameters of rock mass is reached. An example taken from the Three Gorges Project of Yantze River has shown the application significance in rock engineering.

Rock mass rating

Geological Strength Index

Three gorges

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