Applied Mechanics and Materials Vols. 71-78

Abstract: Based on similarity theory and model test, this paper proposes the empirical formula of chemical grouting pressure in porous media that mainly reflects the characteristics of grouting machine, grouting materials, and the propriety of geotechnical medium. This formula reflects the complex grouting process in a simple way. And the orthogonal experiment results indicate that the factors affecting grouting pressure are the permeability of rock mass, grout viscosity, and grouting pump flow. Based on the empirical formula, and according to the achievement in fluid mechanics, this paper further studies and proposes the empirical formula of grouting pressure influenced by pipelines

Abstract: Cracking is a common phenomenon in long concrete structure. But for hydraulic structure it is not permitted because crack will cause heavily seepage and other disaster. Temperature control is an important way to prevent cracking. As for a long deck which has to be constructed in summer, temperature control and crack prevention is a hard work. With the aid of finite element method for temperature field and stress field simulation, research is carried out for a long deck of a pump station. Different measures, such as pipe cooling, surface preservation and pouring temperature control, are tried to control the temperature and stress. The simulation results of different measures composite schemes are analyzed. At last the optimized measures are proposed and its application at site shows it’s successful.

Abstract: The Mg-12Gd-2Y-0.5Sm-0.5Sb-0.5Zr (wt.%) alloy was prepared by casting technology. The microstructure of alloy was then investigated after T6 heat treatment. The results show that at 523K, the alloy has shown the superior tensile strength (i.e. 345.5 MPa). When experimental alloy was stretched with temperature increasing from 293K to 523K, the increases of deformation strengthening and critical crack propagation stress caused the anomalous temperature dependence of tensile strength.

Abstract: A general numerical simulation method is presented for the analysis of the dynamic interaction problem between a large-span concrete culvert, discretized by a plane strain finite element model (FEM), and a dynamic system of vehicle traversing at various speeds. The vehicle is represented as a mass-spring-damper FEM system with seven degrees of freedom. The time-variable coupled dynamic system is solved by a step-by-step solution technique using Newmark’s integration scheme. The backfill soil elastic modulus is modeled as varying linearly with depth below the ground surface. Several numerical examples are investigated by modifying different parameters such as backfill height and road surface stiffness, respectively. The dynamic displacement response for the mid-span point of the concrete culverts is analyzed, as well as the displacement impact factor. The research results demonstrate that the impact factor changes with the vehicle speed and strongly depends on the road surface roughness conditions.

Abstract: The overburden of high embankment culvert is over 10 m, such high fill always leads large earth pressure on the slab of the culvert. The imperfect ditch covered with geogrid method was employed to reduce the vertical earth pressure on the slab. A series of numerical analyses were performed to investigate the load reduction effect of the imperfect ditch. In the simulation, the number of geogrid layers, the geometry of the load reduction ditches, as well as the location and the stiffness of the geogrid are investigated to analyse the influences on the vertical earth pressures. The results show that the slope angle and the height of the ditch, the plane stiffness of the geogrid have great effect on the load reduction efficiency, ditches with higher height and a slope of 90°lead to a significantly reduction on vertical earth pressures on the crown of culverts. The width of load reduction ditch, number of geogrid layers, the location and spacing of the geogrids have little effect on load reduction, the results can provide references for load reduction of slab culvert.

Abstract: Comprehensive evaluation method for interchange project is built on the basic principle and the solution process of the projection pursuit algorithm. The method can determine directly the objective weights of the indexes from the project of being evaluated, and avoid the subjective negative impact on the conclusion of the determining index weights and the conclusion influenced by the index weights given by people themselves in other evaluation methods. Real coding based Accelerating Genetic Algorithm (RAGA) is proposed and applied to deal with global optimization problem of high-dimensional data effectively by optimizing the projection index function and searching for the optimal projection directional vector.

Abstract: A finite element reinforced concrete model has been analyzed by the author with Ansys v.9 finite element program for both unstrengthened and CFRP-strengthened hollow columns using solid65 concrete element, its size 24x26x24 mm and Link8 discrete steel distribution element. The CFRP has been modeled using Solid46 element, which has orthotropic properties. The deflection results have been compared with an experimental and other finite element model which are performed by Lignola [6], in which using Tno Diana v. 9.1 finite element program for modeling concrete using three-dimensional solid brick element type Chx60, steel using embedded reinforcement truss element and CFRP using three-node plane bonded element. These results show that the author's model is much better than the Lignola's [6] model comparing with the experimental one. A parametric study has been done on the proposed model for obtaining the effect of using the GFRP instead of the CFRP in column strengthening by comparing the failure loads and the concrete and steel properties at failure. This study show a reduction in the failure load values by an amount 0.6 to 2.8% when using GFRP, indicating that the CFRP is more preferable in strengthening of the hollow column than the GFRP.

Abstract: A general numerical simulation method is presented for the analysis of the dynamic interaction problem between a large-span concrete culvert, discretized by a plane strain finite element model (FEM), and a dynamic system of vehicle traversing at various speeds. The vehicle is represented as a mass-spring-damper FEM system with seven degrees of freedom. The time-variable coupled dynamic system is solved by a step-by-step solution technique using Newmark’s integration scheme. The backfill soil elastic modulus is modeled as varying linearly with depth below the ground surface. Several numerical examples are investigated by modifying different parameters such as backfill height and road surface stiffness, respectively. The dynamic displacement response for the mid-span point of the concrete culverts is analyzed, as well as the displacement impact factor. The research results demonstrate that the impact factor changes with the vehicle speed and strongly depends on the road surface roughness conditions.

Abstract: The elastic-plastic constitutive relationship and the Drucker-prager yielding criterion are used to simulate the behaviour of non-linear geo- materials. Dynamic change laws of abutment pressure of S₂S₂ work face of xiaokang coal mine is simuluted by the ansys program. It is shown that the distribution of abument pressure can be divided into two zones, elastic region and plastic region. The front inside the 13m distance is plastic zone. The zone outside 13m distance is elstic zone. The affecting scope is 144m when the concentrated coefficient of abutment pressure is 5%. The affecting scope is 160m when the concentrated coefficient of abutment pressure is 3%. The simulation provides a reference bases for the application and promotion of thick seam mining technology.

Abstract: Based on the strong danger and great difficulty characteristics of coal pillars mining under strong ground pressure in Datong coal district, the observations on the No.311 coal face in Tongjialiang coal mine were carried out by the method of drilling bits. The key zone of ground pressure prone was determined and the effective unloading measures by blasting were also taken to mining coal pillars by fully mechanized mining technique.