Applied Mechanics and Materials Vols. 105-107

Abstract: The research of stability of underground structures under earthquake action is one of the hot topics in Geotechnical Engineering researches .Through numerical simulation the article studies the dynamic response rules of the underground structure under vertical earthquake action. The result shows that under vertical earthquake action the vertical stress on the roof and bottom plate of underground structure and the same depth in the earth both increases, and the vertical stress on the roof and bottom plate of underground structure is much higher than that on the same depth in the earth (above two times); under vertical earthquake action the underground structure experiences greater vertical stress from time to time, and produces vertical compressive deformation, and sometimes it completely separates from the above soil layer.

Abstract: The failure damage of granite under axial load are caused by the propagation and coalescent of cracks at mesoscale, so it is of important theoretical value and practical significance to to understand the mechnical properties of rock by experimental research on meso damage of granite. The microfracturing process of the pre-crack marble sample on surrounding rock in immerged Long-big tunnel in Jinping Cascade II Hydropower Station under uniaxial compression is recorded by using the testing scheme. According to stereology theory, the propagation and coalescent of cracks at meso-scale are quantitatively investigated with digital technology. Therefore, the basic geometric information of rock microcracks such as area, angle, length, width, perimeter, is obtained from binary images after segmentation. The results show that the new meso-mechanical testing scheme on rock meso-damage could be used to quantitatively analyzed from the geometric information of rock microcracks.

Abstract: Composite soil-nailing is a new technology developed from abroad in recent years, to be used in excavation of soil, slope stability. This paper studied the stress and deformation of composite soil nailing wall by nonlinear FEM. According to the structure characteristic, the finite element analysis for composite soil nailing construction process is carried out. Based on geotechnical elastic-plastic constitutive model, the adopted failure criterion was a composite Drucker-Prager criterion with tension cut-off. A kind of rotational Goodman interface element is employed to simulate the behavior of interface between the soil-mixed cement which forms the barrier of seepage flow along the boundary of foundation pit, and soil ground. Through the comparative analysis with on-site monitoring data, the finite element calculation results have good precision.

Abstract: Abstract: The method of system identification has been initially applied in the field of the shipbuilding, especially in the application of the ship maneuverability.This article established the mathematical model of system identification of composite trimaran pitching motion model based on the genetic optimization algorithm, using VB language to write the recognition software, Design and produce a composite trimaran test model, doing the free pitching decay test ,then completing the pitching motion system identification according to the test data, and got the pitching motion equation which will be used to do the forecast ,the results of forecast can well match with the test results,confirmed the feasibility of this set of identification method, laid the foundation for other sway motion research of composite trimaran.

Abstract: The embedded length of anti-slide piles reinforcing slopes is analyzed by three-dimensional elasto-plastic shear strength reduction finite difference method. The effect of embedded pile length on safety factor and pile behavior, and the effects of the pile spacing, pile head conditions, bending stiffness and soil style on pile length and pile behavior are analyzed. The results show that the pile spacing and the pile head conditions have significant influence on the critical pile length. The critical pile length is seen to increase with decreasing pile spacing, and smaller pile spacing tends to increase the integrity of the piled slopes. A theoretical analysis of the slip surface is also described, and the slip surface determined by the pressure on piles considering the influences of both soil and the piles of slopes is in agreement with previous researches.

Abstract: In this work, the degradation of Rhodamine B by hydrogen peroxide under microwave irradiation is studied and the optimum conditions are designed by single factor experiment. The UV-VIS spectral changes of RhB solution is detected under the optimum conditions. The results indicate that microwave induction can efficiently improve the oxidative degradation of RhB by hydrogen peroxide in alkaline solution, espcially the dye has the best photodegradation efficiency more than 99% when the concentration of RhB was 300mg/l and the pH of solution was 12 after irradiated for 10min, It is better than RhB under visible irradiation in alkaline environment with hydrogen peroxide. The solution initial pH has no effect on the temporal absorption spectral of RhB. The process of reaction conforms to the first-order kinetic equation.

Abstract: Based on the test results, the wave velocity and the attenuation rule of elastic wave of weathered zone in Longmen Grottoes are studied. The wave velocity decreases with the increasing of the attenuation coefficient in a certain range. When wave velocity decreases to a certain value, there is not a relationship between wave velocity and attenuation coefficient. The attenuation coefficient thresholds of P-wave 0.01and S-wave 0.1 separate good rockmass quality from poor rockmass quality. The test results show that the elastic wave velocities of the surrounding rocks are generally high, which indicates that the rockmass skeleton is solid. But the rockmass anisotropy is obvious, which indicates that the structure planes are more developed. The results of the study are important for the protection of historical relics.

Abstract: A meso-mechanical testing scheme based on scanning electron microscopy(SEM) is developed to carry out the experiment of microfracturing process of rocks. The microfracturing process of the sample on surrounding rock in immerged Long-big tunnel in Jinping Cascade II Hydropower Station under uniaxial compression is recorded by using the testing scheme. According to digital image processing theory, the meso-structural information of rock microfracture such as length, angle, area, etc are obtained from SEM images. Then, the meso-structural information of microfracturing process under uniaxial compress is analysized and the distribution regularities of microfracture parameters are generalized extreme value distribution with variable parameters. The process was described of the damage from the perspectives of macro-and micro-scale under the uniaxial compression loads.

Abstract: With the full consideration of the heterogeneity, existing joints, and cracks in the rock, the coupled gas-rock model for investigating the failure process of coal-rock is established by introducing the related equations governing the evolution of stress, damage and gas permeability along with the deformation of coal and rock. A numerical approach of realistic failure process analysis (RFPA) to simulate the stratum movement, layer separation, the whole collapse progresses, and gas permeability changing of the protected coal seam is proposed. The numerical simulation results well displayed the whole processes of the cracks growth of gas seepage passage and the change of gas permeability for the closed distance protected coal seam. It can be seen from the distribution of acoustic emission in the space that the stratum failure is transferred from deeper to surface. By the analysis of the stress fields changing, the reasons of the gas permeability improvement of the protected coal seam are presented.

Abstract: The damage caused by blasting vibration on rock mass is an extremely complex process, and has certain impact on the mechanical properties and bearing capacity of the rock, which will affect the overall stability and safe operation of the construction. Therefore, studying on the damage effect of blasting vibration is very necessary. Taking Laxiwa hydropower station project as a background, the paper computed relative velocity response spectrum using monitoring and measuring blasting velocity as an excitation, then analysis was carried out to study the relationship between the depth of rock blasting and the integral value of relative velocity response spectrum as well as the index of cooperation of the integral value and the blast vibration’s duration time. The results show that using three-parameter (velocity, frequency, duration time) was clearly superior to two-parameter (velocity, frequency) on studying the damage fracture of rock blasting, and two-parameter was better than one-parameter (velocity) by analogy.