Applied Mechanics and Materials Vols. 204-208

Abstract: In order to fully investigate dangerous sections, implement Security engineering, and reduce accidents, based on the analysis of road and traffic characteristics of rural highway, methods of identifying dangerous road and sections of rural highway are put forward. With the application of Variable Weight Comprehensive Evaluation and Fuzzy Mathematic Comprehensive Analysis method, the methods are raised in mountainous areas and common areas under the conditions of no accident data. Based on the accident data, the methods used different range come up with Quality Control-Identify Index method, Fuzzy Evaluation method, and Double Variables Filtration method. Among them, the Fuzzy Mathematic Comprehensive Analysis method is a new method of evaluation road safety degree According to the traffic and road characteristics of rural highways. These methods provide a scientific theory method for the grass-roots workers, offer the theory basis to the implementation of Safeguards engineering, and enhance the economical rationality of implementing Safeguards engineering, achieving the best economic benefit.

Abstract: To study the applicability of dynamic compaction for loess subgrade, the model test had been done. According to the test results, some conclusions were drawn out as follows: dynamic compaction can improve the density of loess in a short time, the lateral effective compaction width of loess was narrowed with the depth of loess deepened. In the same depth of soil, the density was improved with the tamping times, and the lateral compaction width was relevant to the distance between tamping pit and discussing spot.

Abstract: Subgrade consolidation settlement was the basic content of deformation monitoring and settlement assessment for the railway, controlling settlement deformation was one of the key factors for the project. Based on measured settlement from subgrade, major mechanical parameters about subgrade soil were obtained by finite element method and BP neural network. After obtaining these parameters, finite element calculation would be done for consolidation settlement about subgrade, the deformation from pavement in different periods and post construction settlement and the average degree of consolidation for every stratum would be predicted based on the results, feedback analysis on consolidation settlement for the subgrade would be obtained. The results from it’s application in a railway subgrade project show that: this method may not only obtain rapidly the major mechanical parameters of soil layer, but also predict the consolidation settlement from subgrade reasonably. It can provide a good reference for the design and the operation and the settlement assessment in the railway project.

Abstract: Water and heat conditions and their interactive affections are the key factors for the frost damages of highway engineering. In order to understand the moisture and thermal movement of subgrade soil deeply, a moisture-thermal coupling model has been developed for analyzing the temperature distribution in the permafrost subgrade of highway. The model takes into account both the effects of heat generation, internal conduction and convection, and the moisture movement to accurately predict the temperature evaluation. The theoretical calculations are compared to in-situ test results for the Qinghai_Tibet Highway and shown to be in great agreement at accuracy and precision. The coupling model can serves for the prediction of the frost depth of permafrost subgrade, further prevent the highway engineering from damages.

Abstract: The article designed optimum asphalt aggregate ratio of asphalt mixture by mechanical index method, the purpose of the mechanical index method is that the bond strength and internal friction angle of asphalt mixture can reach a best balance, the shear stress reaches the maximum, so the results have a good effect for preventing rut. The research indicated that the surface layer performance of asphalt mixture which designed by the mechanical index method is better than by the traditional Marshall method, so the mechanical index method is a simple and effective method.

Abstract: In this paper, firstly, based on asphalt pavement central layer, the comparison with the foreign related gradation of asphalt mixtures, one typical kinds of gradations are decided; Secondly, the asphalt aggregate ratio is predicted based on professor Lin’s Theory , and five asphalt aggregate ratio are selected. Finally, the road performance of asphalt mixture is experimented, and the road performance of five asphalt aggregate ratio is analyzed. As a result, we can predict the range of the optimum asphalt aggregate ratio based on the road performance.

Abstract: Using the finite element method, influences of vehicle load, subgrade fillings and compactness on the subgrade work zone were analyzed, of which the traffic load impacts most. Considering the traffic and mechanical character of the subgrade, it is determined that the appropriate subgrade work zone depth of rural highway is 1.0m. As a result, applying proper work zone depth plays an important role in the construction cost of rural highway.

Abstract: Based on the data obtained in the in-situ test of layered settlements in Wen-Fu Railway, the settlement regulation of the thick-layer soft soil treated by the composite structure of PHC pile-net is analyzed, and two calculation models are utilized to predict the final settlement. Since the predicted settlement is far less than the value required by the standard, the treatment method for the deep soft soils is proved to be reasonable. After that, according to the mechanism of the composite structure of PHC pile-net, the settlement values are calculated using various common calculation methods and the results are compared to the corresponding experimental data. The applicability of these methods is discussed and then the settlement calculation method of the thick-layer soft foundation treated by the composite structure of PHC Pile-net is obtained. The series of conclusions finally given provide the basis for the theoretical research and optimum design of pile-net composite foundation.

Abstract: Aimed at the supporting problems in the fully mechanized roadway with large mining height of the specially thick coal seam in workface 8105 in Tashan coal mine, the “three highs with one low” supporting technology of high strength, high stiffness, high reliability and low support density was adopted to solve the roadway supporting problems of specially high coal side and specially large section and effectively control the surrounding rock deformation and ensure the roadway safety. It also increased the roadway excavation speed which made good conditions for fast advance of the fully mechanized workface, and it made the soft-rock roadway supporting technology in Datong mine area develop into a new level.

Abstract: The parameters of dynamic compaction impacting on consolidation effect such as fall-height of hammer, impact mode, impact space, etc. are analysed by dynamic FEM method. The method of choosing parameters of dynamic compaction and consolidation effect of dynamic compaction on filling subgrade are illuminated by field test. Conclusions are drawn: with the increase of impact energy, the range of plastic deformation zone will extend to a certain depth in subgrade, which will certainly expand the effective reinforcement range of subgrade; optimal impact times of a subgrade is available; the consolidate depth and influencing area by light hammer with heavy impact is less than that by heavy hammer with light impact when impact energy is equal; with the increase of hammer diameter, both deformation and strain of subgrade reduce under the same impact energy.