Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the...Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0 5 m zone behind the abutment should be specially designed. The results of the study from vehicle track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction(K30) is greater than 190 MPa within the 0 5 m zone behind the abutment and greater than 150 MPa in other zones.展开更多
In the zones of high seismic activity, tailings dam should be assessed for the stability against earthquake forces. In the present paper, a simplified method is proposed to compute the factor of safety of tailings dam...In the zones of high seismic activity, tailings dam should be assessed for the stability against earthquake forces. In the present paper, a simplified method is proposed to compute the factor of safety of tailings dams. The strain-dependent dynamic properties are used to assess the stability of tailings dams under seismic conditions. The effect of foundation soil properties on the seismic stability of tailings dams is studied using the proposed method. For the given input parameters, the factor of safety for lowfrequency input motions is nearly 26% lower than that for high-frequency input excitations. The impedance ratio and the depth of foundation have significant effect on the seismic factor of safety of tailings dams. The results from the proposed method are well compared with the existing pseudo-static method of analysis. Tailings dams are vulnerable to damage for low-frequency input motions.展开更多
There are a number of geotechnical systems used at open cut operations of Anglo American's Metallurgical Coal business unit in Australia. These systems are mainly mine site specific, based on geological informatio...There are a number of geotechnical systems used at open cut operations of Anglo American's Metallurgical Coal business unit in Australia. These systems are mainly mine site specific, based on geological information and used as hazard plans. They are qualitative and reliant upon the experienced judgement of site based engineers and the general workforce. They are not suitable for calculating the associated risks of geological structures and mining responses. A uniform risk rating system that can be used to provide an unbiased, standard and quantifiable assessment of the risk from highwall and lowwall failures is therefore developed using the experience gained with such systems in Anglo American's South African operations. This system is a semi-quantitative risk rating system and takes into account the relative differences in the importance of hazards as experienced at each mine site as a result of different combinations of geotechnical factors and mining conditions. It is based on critical geotechnical and other parameters that have been identified by site mining engineers, geologists and geotechnical engineers. The primary advantage of this risk rating system is that all open cut mines in the Anglo American's Metallurgical Coal operations use a near identical system, which enables the user to compare the risk after each blast and with other mines. The system can be adjusted to meet local mine specific requirements. The implementation of this system, a computer program that automatically calculates the risks and recommends predetermined controls, has been made as practical and as easy to use as possible. This program can be used by personnel from other mining disciplines not directly related to geotechnical engineering.展开更多
A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil archi...A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which was quantified by the load transfer factor in the limited equilibrium analysis. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, an extension modification of the deterministic method into a probabilistic method is developed in this paper. The MCS （Monte Carlo simulation） with log-normal random variables has been employed to calculate the probability of failure （Pf） for the drilled shafts/slope system. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Finally, a case study has been performed to illustrate the application analysis of the developed probability approach in drilled shafts/slope system.展开更多
The shear strength parameters of soil （cohesion and angle of internal friction） are quite essential in solving many civil engineering problems. In order to determine these parameters, laboratory tests are used. The ...The shear strength parameters of soil （cohesion and angle of internal friction） are quite essential in solving many civil engineering problems. In order to determine these parameters, laboratory tests are used. The main objective of this work is to evaluate the potential of Artificial Neural Network （ANN） and Regression Tree （CART） techniques for the indirect estimation of these parameters. Four different models, considering different combinations of 6 inputs, such as gravel %, sand %, silt %, clay %, dry density, and plasticity index, were investigated to evaluate the degree of their effects on the prediction of shear parameters. A performance evaluation was carried out using Correlation Coefficient and Root Mean Squared Error measures. It was observed that for the prediction of friction angle, the performance of both the techniques is about the same. However, for the prediction of cohesion, the ANN technique performs better than the CART technique. It was further observed that the model considering all of the 6 input soil parameters is the most appropriate model for the prediction of shear parameters. Also, connection weight and bias analyses of the best neural network （i.e., 6/2/2） were attempted using Connec- tion Weight, Garson, and proposed Weight-bias approaches to characterize the influence of input variables on shear strength parameters. It was observed that the Connection Weight Approach provides the best overall methodology for accurately quantifying variable importance, and should be favored over the other approaches examined in this study.展开更多
基金Project(41030742) supported by the National Natural Science Foundation of ChinaProject(2009G010-c) supported by the Technological Research and Development Programs of the Ministry of Railways,China
文摘Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0 5 m zone behind the abutment should be specially designed. The results of the study from vehicle track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction(K30) is greater than 190 MPa within the 0 5 m zone behind the abutment and greater than 150 MPa in other zones.
文摘In the zones of high seismic activity, tailings dam should be assessed for the stability against earthquake forces. In the present paper, a simplified method is proposed to compute the factor of safety of tailings dams. The strain-dependent dynamic properties are used to assess the stability of tailings dams under seismic conditions. The effect of foundation soil properties on the seismic stability of tailings dams is studied using the proposed method. For the given input parameters, the factor of safety for lowfrequency input motions is nearly 26% lower than that for high-frequency input excitations. The impedance ratio and the depth of foundation have significant effect on the seismic factor of safety of tailings dams. The results from the proposed method are well compared with the existing pseudo-static method of analysis. Tailings dams are vulnerable to damage for low-frequency input motions.
文摘There are a number of geotechnical systems used at open cut operations of Anglo American's Metallurgical Coal business unit in Australia. These systems are mainly mine site specific, based on geological information and used as hazard plans. They are qualitative and reliant upon the experienced judgement of site based engineers and the general workforce. They are not suitable for calculating the associated risks of geological structures and mining responses. A uniform risk rating system that can be used to provide an unbiased, standard and quantifiable assessment of the risk from highwall and lowwall failures is therefore developed using the experience gained with such systems in Anglo American's South African operations. This system is a semi-quantitative risk rating system and takes into account the relative differences in the importance of hazards as experienced at each mine site as a result of different combinations of geotechnical factors and mining conditions. It is based on critical geotechnical and other parameters that have been identified by site mining engineers, geologists and geotechnical engineers. The primary advantage of this risk rating system is that all open cut mines in the Anglo American's Metallurgical Coal operations use a near identical system, which enables the user to compare the risk after each blast and with other mines. The system can be adjusted to meet local mine specific requirements. The implementation of this system, a computer program that automatically calculates the risks and recommends predetermined controls, has been made as practical and as easy to use as possible. This program can be used by personnel from other mining disciplines not directly related to geotechnical engineering.
文摘A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which was quantified by the load transfer factor in the limited equilibrium analysis. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, an extension modification of the deterministic method into a probabilistic method is developed in this paper. The MCS （Monte Carlo simulation） with log-normal random variables has been employed to calculate the probability of failure （Pf） for the drilled shafts/slope system. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Finally, a case study has been performed to illustrate the application analysis of the developed probability approach in drilled shafts/slope system.
文摘The shear strength parameters of soil （cohesion and angle of internal friction） are quite essential in solving many civil engineering problems. In order to determine these parameters, laboratory tests are used. The main objective of this work is to evaluate the potential of Artificial Neural Network （ANN） and Regression Tree （CART） techniques for the indirect estimation of these parameters. Four different models, considering different combinations of 6 inputs, such as gravel %, sand %, silt %, clay %, dry density, and plasticity index, were investigated to evaluate the degree of their effects on the prediction of shear parameters. A performance evaluation was carried out using Correlation Coefficient and Root Mean Squared Error measures. It was observed that for the prediction of friction angle, the performance of both the techniques is about the same. However, for the prediction of cohesion, the ANN technique performs better than the CART technique. It was further observed that the model considering all of the 6 input soil parameters is the most appropriate model for the prediction of shear parameters. Also, connection weight and bias analyses of the best neural network （i.e., 6/2/2） were attempted using Connec- tion Weight, Garson, and proposed Weight-bias approaches to characterize the influence of input variables on shear strength parameters. It was observed that the Connection Weight Approach provides the best overall methodology for accurately quantifying variable importance, and should be favored over the other approaches examined in this study.
