Applied Mechanics and Materials Vols. 90-93

Abstract: At the turn of the last century, bolt supporting of coal roadway had rapidly developed with the applied range of bolt stretching continually. The bolt supporting in roadway has been implemented widely. But until now, there is no reliable theoretical support or appraisal system on the design of bolt supporting roadway and the evaluation of supporting conditions. Supporting effect is tested only by practice and roof-fall accidents take place repeatedly. This paper conducts the research on the bolt supporting parameters in No.315 transportation-up-hill roadway of Nan Ye Coal Mine with numerical analysis method; it is discovered that numerical analysis can be a good way to predict and evaluate roadway supporting effects to be worthy popularizing.

Abstract: In this paper, the combination of antenna array detection method of ground penetrating radar is put forward to solve the actual engineering problem that it is difficult to monitor the length of CFG pile. The experiments of length of six CFG piles find that the relative error of the length is 5.26%. The result indicates that it is enough reliable to determine the pile length by using the GPR method and can meet the engineering needs. Furthermore, the effect of the mix proportion, moisture content on the monitoring quality is obtained.

Abstract: On May 10, 2007, the Muzhuping landslide moved into Modao-he River caused by impoundment and early rainfall, which is a first landslide hazard in the Shuibuya Reservoir. Using ABAQUS software to analysis the mechanism of deformation with considering the coupling Seepage-stress, and by according to residual thrust method, some predictions of the slope stability were performed with considering to fluctuation of the reservoir water. The numerical results show that the initial impoundment and rapid declining of reservoir water level are most dangerous for a reservoir.

Abstract: This paper analyzed the interaction between two parallel vertical cracks in a transversely isotropic half space by using the boundary element method (DBEM). The crack surface is perpendicular to the free surface and isotropic plane subjected to normal and tangential uniform distributed load respectively. The stress intensity factor (SIF) values of the crack are calculated from the crack opening displacements. And the interaction effect factor of SIF values is employed to quantitatively describe the interaction between two cracks. The variations of interaction effect factor are investigated with the distances between cracks, the side ratios and free surface. Results show that the existence of the free surface exerts more obvious influence on the SIF values of the crack close to free surface in half space than those in infinite medium. But the free surface has almost no influence on the interaction between two cracks.

Abstract: In order to know about the rheological properties of typical biotite granitic gneiss in Xiaowan Hydropower Project, triaxial rheological experiments with biotite granitic gneiss were carried out on the rock servo-controlling rheological testing machine. As a result the typical complete rheological curve of the biotite granitic gneiss indicates that when the stress level is low, the rheological deformation of rock specimen is not obvious; when in high stress conditions, the rock mass rheological properties are very significant with large rheological deformation, including three typical rheological phases. The rheological deformation decreases with the increase of the confining pressure, and at the same time the rheological rate of rock specimen changes with the change of stress level. In low stress state, the corresponding rheological rate of the rock specimen incarnated as the rheological rate attenuation stage and the rheological rate uniform stage, while once the stress level exceeds the long-term strength of rock specimen, the rheological rate would first decreases and then keep at a constant value, and finally it will trend to follow the non-linear acceleration law. The rupture form of the low-intensity biotite granitic gneiss specimen is the main crack surface which causes the damage of rock specimen, and finally generated by the expansion and transfixion of the crack in the initial cavern flaw. The rheological deformation and rupture form of rock specimen in different confining pressures are not exactly the same.

Abstract: Through the test research of the two different molding methods of vibration and static pressure, including the analysis of traditional heavy compaction and the new vibration compaction, we could see that the result of the vibration could satisfied the field construction. Analysis of mechanical property was 7d unconfined compressive strength, at the same dose of cement, the strength of vibration was higher than the static pressure method’s and it was more rational and effective for the field control of the construction. Evaluation of water stability was up to the 28d and 5 times freezing-thawing tests, and the resistance ability against frost of vibration was better than the static pressure method. So adopting the vibration method could improve the resistance performance against frost of the road in northeast region of freezing-thawing in spring. From the 7d dry shrinkage test we got that the adopting the vibration method the resistance performance of dry shrinkage was much better and could improve the resistance against shrinkage of the road.

Abstract: Parameter-M is the proportion factor of horizontal soil reaction when the soil is compressed horizontally, and the corresponding method of pit retaining structure analysis is named as M-method. M-method is widely used to determine the working state of pit retaining structures in China, however, parameter-M varies significantly when deduced by different approaches. An analysis unit is chosen in the subway station pit in Zhengzhou, center of China, on the bank of Yellow River. The retaining structure consists of reinforced concrete piles, internal bracing struts made of steel pipes. The horizontal displacements of retaining piles and the axial forces in pipe bracing struts are monitored in-situ. Then, calculation assumption is taken as that during the elastic deformation stage, parameter-M for each soil keeps constant. Then a series of equilibrium equations of forces acting on retaining structure are set up to determine the values of M for each soil corresponding to deferent stages of excavation. When the identified values of M are applied in the later projects, it shows the validity and accuracy of the method. Precise values of M are applied in the similar geological sites to optimize the retaining structure design.

Abstract: The paper has in-depth systematically studied stability and early warning of high engineering high slopes in depth, and established the early early-warning model of slope and the health diagnosis system. The results show that: ① displacement deformation increases with time and decreases with increasing depth. Changes of displacement can be divided into three stages: deformation rapidly increases in the early, and slowly increases in the medium term, and becomes gradually stable in the later; ② by through stability analysis of Mayanpo slope of Mayanpo slope ofby finite element strength reduction FEM, stability coefficient is 1.72; ③ Using using boundary displacement method and taking the equivalent plastic strain region through as a criterion for the early- warning analysis of slope landslide landslide, the paper presents establishes the early-warning monitoring system of slope based on double controlleding indicators of displacement deformation amount and safety factor.

Abstract: The socketed depth in rock-socketed pile can influence its bearing mechanism largely. At present the numerical simulation is used to study the socketed depth’s influence on pile’s bearing mechanism. It can reveal the pile bearing mechanism in some degree; however, there are some defects and limitations in simulation for its assumptions and simplifications. Based on the pile foundation of Tian-xing-zhou Bridge, the model test is conducted to study the socketed depth’ influence on rock-socketed pile bearing mechanism. In the model test, the socketed depth of model piles are made different ranging from 60mm to 200mm at the step of 20mm, and the bed rock is simulated with mixture of sand and plaster, the rock-soil overlain the bed rock is simulated with silty sand, the pile is simulated with organic glass rod according to similarity principle respectively. The results show that the settlement of top of model pile is smaller and the ratio of point resistance is smaller when the socketed depth is longer. When the socketed depth reaches 5D (D represents diameter of model pile), the ratio of point resistance is no more than 40%, and it is less than 1% when 8D. The conclusions drawed from model test are useful to deciding the length of pile foundation in Tian-xing-zhou Bridge.

Abstract: This paper propose genetic algorithm combined with neural networks, greatly improving the convergence rate of neural network aim at the disadvantage of the traditional BP neural network inversion method is easy to fall into local minimum and slow convergence.Finally, verified the feasibility and superiority of the above methods through the successful initial ground stress inversion of actual project.