Papers by Author: Qing Wen Ren

Abstract: Infilling rock joints widely exist in natural rock masses, and the shear failure of infilling rock joints plays an important role in the instability of rock masses. In order to study the shear failure mechanism of infilling rock joints, Particle Flow Code is used to simulate the direct shear test of infilling rock joints. The PFC models with different infilling thickness are established firstly, and then the procedures of PFC simulation are described. In the end, the shear failure process of infilling rock joints with different infilling thickness is simulated. Based on the PFC simulation results, it can be concluded that the shear failure mode changes with increasing infilling thickness, and the shearing of the infilling rock joint rarely gives birth to microcracks in rock due to the existence of the infilling material.

Abstract: The calibration of micro-properties of bonded particle model (BPM) is usually artificially accomplished by the means of trial and error which has some intrinsic drawbacks such as high time consumption, arbitrariness, uncontrolled accuracy, etc. In order to overcome these shortcomings, the optimization inversion method based on the asynchronous particle swarm algorithm is proposed to estimate the micro-properties of BPM in PFC. The optimization model is firstly established by formulating the objective function and related constraint conditions, and then the procedure of optimization inversion is presented. Furthermore, a FORTRAN program called PIBPM is developed for the realization of the proposed method. The feasibility of the proposed method and the correctness of PIBPM are verified through an application example.

Abstract: The stability of rock masses is controlled by the shear behavior of rock discontinuities, and it is hard to investigate the shear behavior of rock discontinuities at micro-scale by using traditional physical test method. With this in mind, Particle Flow Code is used to simulate the direct shear test of rock discontinuities. The PFC model of rock discontinuities is established firstly, and its micro-properties are inversed by using the proposed optimization inversion method based on the asynchronous particle swarm algorithm. Then, the PFC simulation of shear behavior of rock discontinuities is performed. The simulation results show that the number of microcracks gradually increases with the increasement of shear displacement, and the accumulated microcracks result in the shear failure of rock discontinuities.

Abstract: The failure of concrete dam is a process started from local failure to global instability, and there is a huge scale difference in the process, so the analysis should be conducted in a multiscale manner. Choosing a typical failure curve as a signal, the precursor load is determined in the form of singularity point in the curve. With a numerical example, the previous reported methods for determining precursor load are compared with the wavelet approach, and it is shown that the wavelet approach gives more accuracy and reasonable results. Besides the precursor load, the failure mode, local failure or global instability, can also be figured out by the wavelet approach. By applying it to the Jinping arch dam, the obtained results are in good consistency with geology mechanical test. It is shown that the wavelet approach is of good applicability and accuracy for dam failure analysis.

Abstract: For the instability problem of gravity dam sliding along base surface, cubic nonlinear constitutive model of soft material in base surface is adopted, which is usually expressed by Weibull model. Dynamic Equations of dam sliding along base surface is established. By means of catastrophe theory, the jumping and hysteresis phenomena of the vibration amplitude of the dam is analyzed, the parameter range of stable region in which amplitude doesn’t happen catastrophe is given and the factors which cause amplitude instability are discussed. The results obtained in the paper are of significant value for understanding the sliding instability mechanism of gravity dam under earthquake, as well as guiding the design of gravity dams.

Abstract: In this study, an experiment program is presented to study the bonding mechanism between corroded bolts and grout and in particular the influence on bonding behavior in terms of different corrosion sections along anchor. With respect to four groups of manufactured bolt specimens, the noncorroded and the corroded, respectively, on the front, middle and rear section along anchor, a pullout test is conducted to reveal the relationship between load and loading-end slip and to investigate the bond-stress distribution characterization along full anchor. Experimental results show that corrosion product, acting as lubricating effect at the interface between bolts and grout, can result in the degradation of bonding mechanical behavior. Meanwhile, corrosion on different sections along anchor has a different effect on the anchorage capacity of bolts. Especially, corrosion on the front section induces the greatest decrease of anchorage capacity of bolts. Thus, it is concluded that the front section along anchor is the key region affecting the bonding mechanical behavior between bolts and grout.