Applied Mechanics and Materials Vols. 256-259

Abstract: The mechanics parameters of a slope are difficult to determine accurately by conventional methods, because of weathering, fracture and excavation induced stress release. Based on the orthogonal test and three-dimensional numerical calculation to get the learning samples of displacement, By using the neural network method to obtain the relationship between the mechanical parameters and displacement, Combined with measurement results of deformation in the field mining, Obtained the reasonable strata parameters to provide the basis for slope treatment.

Abstract: Since rock masses are not a true continuous, homogeneous, isotropic and linear-elastic (CHILE) continuum, the loading and unloading behaviors differ greatly from each other. Professor Ha Qiulin and his co-workers have demonstrated that strength and deformational characteristics, initial rock stresses, scale effects, creep, deformation and fracture patterns are quite different and stress path dependence is particularly emphasized. As engineering unloading of the rock mass is essentially of a dynamic nature by excavation, we will first discuss the excavation process and related stabilization techniques. For the complex stress and deformation conditions around the excavated boundaries, it seems rational to define an excavation disturbed zone (EDZ) as in the last decades. In tunnel excavation, temperature and ventilation effects should be also taken into account. Space-and-time dependence on tunnel behaviors is important. Finally, further research topics are discussed.

Abstract: Three new types of reinforced earth structures were introduced including reinforced gabion retaining wall, green reinforced gabion retaining wall and flexible wall face geogrid reinforced earth retaining wall. In order to study settlement behavior of these three retaining walls, lab tests were carried out. Cyclic loading-unloading of different levels (0~50kPa, 0~100kPa, 0~150kPa, 0~200kPa, 0~250kPa, 0~300kPa, 0~350kPa) were imposed. The settlement behaviors of retaining walls were analyzed, and secant modulus when loading and unloading was obtained. Results show that retaining walls present great elastic and plastic deformation, and plastic deformation is greater than elastic deformation. Secant modulus decreases with the increase of loading-unloading cycles under the same loading level. Unloading secant modulus is bigger than loading secant modulus in the same cycle. With the increase of loading level, both elastic and plastic deformation increase, and plastic deformation increases more quickly than elastic deformation.

Abstract: For three-dimensional geological modeling by TP model, the problem of deviation in the original drilling data must be resolved. In this paper, the original logging data of drilling is utilized to study the spatial relationship between the geological bodies constructed by equivalent vertical and real drilling respectively, and a correction method on deviated drilling is therefore proposed. The result shows the method can effectively conduct the lossless correction of deviated drilling under various drilling and stratum conditions, thus providing reliable logging data of drilling without deviation for the construction of TP models.

Abstract: By means of FLAC^3D software, firstly 3-demensional model was built, and stress migration and evolution law of coal seam in the process of mine roadway excavation are studied. Then according to the stress evolution law, the mechanism of acoustic emission (AE) generation in coal after excavation was analyzed. The results show that: after excavation, due to lateral displacement constraints in the coal body near the free face is removed, the coal in this zone was in 2-dementional stress condition. Because the vertical stress exceeded the uniaxial strength of coal body, the coal got into the post-peak strain-softening state. With the evolution of time, the stress in the zone gradually reduced until a state of equilibrium. In this zone the principle of AE generation is that lateral stress reduction result in macro crack propagation, coal mass failure, then elastic wave emitted. Signals come from the zone, i.e. stress relief zone, is the main part of AE signals, and should be the focus of study in AE technology of predicting coal or rock dynamic disasters. In stress-peak zone, due to the constraints of the lateral displacement, the lateral stress and strength of coal increased, the vertical stress of coal body gradually increased until the strength peak in the 3-dimensional stress state. After the excavation of roadway, the stress in stress-concentration and stress-peak zone gradually increased to equilibrium state over time. The principle of AE generation in this region is that due to the increase of the vertical stress, coal and rock gradually damaged that resulted in the release of the elastic wave.

Abstract: Strength, elastic modulus and failure modes of samples with different joint dip angle, joint continuity degree, joint set and joint width under uniaxial compressive load are studied by similar material tests. To the sample with single joint, its strength, elastic modulus and failure mode are controlled by joint dip angle to much extent, and it will shear and slip along or split across joint face to fail, in which sample’s strength and elastic modulus is minimum corresponding to the first failure mode. To the jointed sample with different joint continuity degree, its strength and elastic modulus decrease with joint continuity degree, and effect on sample’s strength is much more serious. With increase of joint set, sample’s strength and elastic modulus gradually decrease. With increase of joint width, strength and elastic modulus decreases, and effect on sample’s strength is much more serious.

Abstract: On the basis of the theoretical framework of breakage mechanics for geo-material ,the fissured loess can be regarded as a composite material consisting of bonded blocks and weakened bands，therefore a fissured loess binary-medium model is formulated. Then the model will be applied to the study of fissured loess. By the numerical calculation, the relationship of stress-strain can be obtained. A comparative analysis between calculation and triaxial test has been done. The results show that there is a good adaptability to apply the binary medium model to fissured loess.

Abstract: Taken an open-pit landslide as an example, the cause of formation and the factors inducing the slope to failure are analyzed. According to deformation characteristic of the landslide, the deformation has been exacerbating with the deep mining in depth, and the deformation has close relationship with the rainfall. Rainwater infiltration, which soften the rock mass and induce the pore water pressure to increase, induce envoke landslides. Through analysis on the factors of landslides, the formation lithology(FL) and precipitation are main factors triggering generation and reactivation of landslides. Meanwhile, the deformation failure mechanism and instability mode of the landslide is obtained, which is the sliding and bending deformation model.

Abstract: In order to study dynamic deformation behavior of green reinforced gabion retaining wall, lab test was carried out and the dynamic loads of 4 frequencies and 4 amplitudes were imposed. The total cycles of dynamic load reached 2 million. Lateral and vertical deformation behaviors of green reinforced gabion retaining wall were investigated, and the main factors which influenced the dynamic deformation behavior and their significance were obtained. Meanwhile, fatigue life analysis on green reinforced gabion retaining wall was made. The results show that dynamic deformation is greatly affected by amplitude and the cycles of dynamic load, not significantly affected by frequency. The maximum lateral and vertical deformation occur in the fifth layer of green reinforced gabion wall. With the increase of train load and train speed, fatigue damage and fatigue life of green reinforced gabion retaining wall can be estimated based on accumulative fatigue damage theory.

Abstract: This paper presents an experimental investigation on the failure surface and plastic potential in deviatoric plane of Bangkok Clay. The results of torsional shear hollow cylinder and triaxial tests with various principal stress directions and magnitudes of intermediate principal stress on undisturbed Bangkok Clay specimens are presented. The obtained stress-strain behaviors assert clear evidences of anisotropic characteristics of Bangkok Clay. Both failure surface and plastic potential in deviatoric plane of Bangkok Clay are demonstrated as isotropic and of circular shape (Drucker-Prager type) which implies an associated flow rule. Concerning the behavior of Bangkok Clay found from this study, the discussions on the effects of employed constitutive modeling approach on the resulting numerical analysis are made.