The main reasons for a breach of trouble-free operation of the subgrade are the different kinds of deformation, such as Wain load impact on subgrade surface, loss of stability to subgrade slope, weight of embankment o...The main reasons for a breach of trouble-free operation of the subgrade are the different kinds of deformation, such as Wain load impact on subgrade surface, loss of stability to subgrade slope, weight of embankment on the base, and partial or complete failure of the railway track due to frost heaving. This paper gives a summary of deformation analysis methods being developed in Russia to estimate the operaling con- ditions of the railway subgrade.展开更多
This paper develops a dual-indicator discrete method(DDM)for evaluating the system reliability performance of long soil subgrade slopes.First,they are segmented into many slope sections using the random finite element...This paper develops a dual-indicator discrete method(DDM)for evaluating the system reliability performance of long soil subgrade slopes.First,they are segmented into many slope sections using the random finite element method,to ensure each section statistically contains one potential local instability.Then,the k-out-of-n system model is used to describe the relationship between the total number of sections n,the acceptable number of failure sections m,the reliability of sections R_(sec),and the system reliability R_(sys).Finally,m and R_(sys)are jointly used to assess the system reliability performance.For cases lacking spatial data of soil properties,a simplified DDM is provided in which long subgrade slopes are segmented by the empirical value of section length and R_(sec)is substituted by that of crosssections taken from them.The results show that(1)DDM can provide the probability that the actual number of local instabilities does not exceed a desired threshold.(2)R_(sys)decreases with increasing n or decreasing R_(sec);that is,it is likely to encounter more local instabilities for longer or weaker subgrade slopes.n is negatively related to the horizontal scale of fluctuation of soil properties and positively related to the total length of subgrade slopes L.(3)When L is sufficiently large,there is a considerable opportunity to meet local instabilities even if R_(sec)is large enough.展开更多
Earthquake-induced landslides along the Dujiangyan-Yingxiu highway after the Ms 8.0 Wenchuan earthquake in 2008 were investigated.It was found that:(1) slopes were shattered and damaged during the earthquake and open ...Earthquake-induced landslides along the Dujiangyan-Yingxiu highway after the Ms 8.0 Wenchuan earthquake in 2008 were investigated.It was found that:(1) slopes were shattered and damaged during the earthquake and open tension cracks formed on the tops of the slopes;(2) the upper parts of slopes collapsed and slid,while the lower parts remained basically intact,indicating that the upper parts of slopes would be damaged more heavily than the lower parts during an earthquake.Large-scale shaking table model tests were conducted to study failure behavior of slopes under the Wenchuan seismic wave,which reproduced the process of deformation and failure of slopes.Tension cracks emerged at the top and upper part of model,while the bottom of the model remained intact,consistent with field investigations.Depth of the tension crack at the top of model is 32 cm,i.e.,3.2 m compared to the prototype natural slope with a height of 14 m when the length scale ratio(proto/model) is 10.Acceleration at the top of the slope was almost twice as large as that at the toe when the measured accelerations on shaking table are 4.85 m/s2 and 6.49 m/s2,which means that seismic force at the top of the slope is twice the magnitude of that at the toe.By use of the dynamic-strength-reduction method,numerical simulation was conducted to explore the process and mechanism of formation of the sliding surface,with other quantified information.The earthquake-induced failure surfaces commonly consist of tension cracks and shear zones.Within 5 m from the top of the slope,the dynamic sliding surface will be about 1 m shallower than the pseudo-static sliding surface in a horizontal direction when the peak ground acceleration(PGA) is 1 m/s2;the dynamic sliding surface will be about 2 m deeper than the pseudo-static sliding surface in a horizontal direction when the PGA is 10 m/s2,and the depths of the dynamic sliding surface and the pseudo-static sliding surface will be almost the same when the PGA is 2 m/s2.Based on these findings,it is suggested that the key point of anti-seismic design,as well as for mitigation of post-earthquake,secondary mountain hazards,is to prevent tension cracks from forming in the upper part of the slope.Therefore,the depth of tension cracks in slope surfaces is the key to reinforcement of slopes.The depth of the sliding surface from the pseudo-static method can be a reference for slope reinforcement mitigation.展开更多
There are two phases in the development of China's high-speed railway after the1990s:the research and experiment phase during the Eighth and the Tenth Five-Year Plan periods;the construction and operation phase du...There are two phases in the development of China's high-speed railway after the1990s:the research and experiment phase during the Eighth and the Tenth Five-Year Plan periods;the construction and operation phase during the Eleventh and the Thirteenth Five-Year Plan periods.This paper regards the Beijing-Shanghai High-Speed Railway as the corner stone in the development of high-speed railway subgrade system,and proposes suggestions and solutions to the problems which may reduce the service life of subgrade.These solutions and methods can be referred to in future railway projects.展开更多
文摘The main reasons for a breach of trouble-free operation of the subgrade are the different kinds of deformation, such as Wain load impact on subgrade surface, loss of stability to subgrade slope, weight of embankment on the base, and partial or complete failure of the railway track due to frost heaving. This paper gives a summary of deformation analysis methods being developed in Russia to estimate the operaling con- ditions of the railway subgrade.
基金supported by the National Natural Science Foundation of China(Nos.52078435 and 51878560)the financial support from the open research fund of MOE Key Laboratory of High-Speed Railway Engineering。
文摘This paper develops a dual-indicator discrete method(DDM)for evaluating the system reliability performance of long soil subgrade slopes.First,they are segmented into many slope sections using the random finite element method,to ensure each section statistically contains one potential local instability.Then,the k-out-of-n system model is used to describe the relationship between the total number of sections n,the acceptable number of failure sections m,the reliability of sections R_(sec),and the system reliability R_(sys).Finally,m and R_(sys)are jointly used to assess the system reliability performance.For cases lacking spatial data of soil properties,a simplified DDM is provided in which long subgrade slopes are segmented by the empirical value of section length and R_(sec)is substituted by that of crosssections taken from them.The results show that(1)DDM can provide the probability that the actual number of local instabilities does not exceed a desired threshold.(2)R_(sys)decreases with increasing n or decreasing R_(sec);that is,it is likely to encounter more local instabilities for longer or weaker subgrade slopes.n is negatively related to the horizontal scale of fluctuation of soil properties and positively related to the total length of subgrade slopes L.(3)When L is sufficiently large,there is a considerable opportunity to meet local instabilities even if R_(sec)is large enough.
基金supported by 973 Program,Grant No. 2008CB425802National Natural Science Foundation of Chinasupported by the Fundamental Research Funds for the Central Universities (SWJTU09ZT04)
文摘Earthquake-induced landslides along the Dujiangyan-Yingxiu highway after the Ms 8.0 Wenchuan earthquake in 2008 were investigated.It was found that:(1) slopes were shattered and damaged during the earthquake and open tension cracks formed on the tops of the slopes;(2) the upper parts of slopes collapsed and slid,while the lower parts remained basically intact,indicating that the upper parts of slopes would be damaged more heavily than the lower parts during an earthquake.Large-scale shaking table model tests were conducted to study failure behavior of slopes under the Wenchuan seismic wave,which reproduced the process of deformation and failure of slopes.Tension cracks emerged at the top and upper part of model,while the bottom of the model remained intact,consistent with field investigations.Depth of the tension crack at the top of model is 32 cm,i.e.,3.2 m compared to the prototype natural slope with a height of 14 m when the length scale ratio(proto/model) is 10.Acceleration at the top of the slope was almost twice as large as that at the toe when the measured accelerations on shaking table are 4.85 m/s2 and 6.49 m/s2,which means that seismic force at the top of the slope is twice the magnitude of that at the toe.By use of the dynamic-strength-reduction method,numerical simulation was conducted to explore the process and mechanism of formation of the sliding surface,with other quantified information.The earthquake-induced failure surfaces commonly consist of tension cracks and shear zones.Within 5 m from the top of the slope,the dynamic sliding surface will be about 1 m shallower than the pseudo-static sliding surface in a horizontal direction when the peak ground acceleration(PGA) is 1 m/s2;the dynamic sliding surface will be about 2 m deeper than the pseudo-static sliding surface in a horizontal direction when the PGA is 10 m/s2,and the depths of the dynamic sliding surface and the pseudo-static sliding surface will be almost the same when the PGA is 2 m/s2.Based on these findings,it is suggested that the key point of anti-seismic design,as well as for mitigation of post-earthquake,secondary mountain hazards,is to prevent tension cracks from forming in the upper part of the slope.Therefore,the depth of tension cracks in slope surfaces is the key to reinforcement of slopes.The depth of the sliding surface from the pseudo-static method can be a reference for slope reinforcement mitigation.
文摘There are two phases in the development of China's high-speed railway after the1990s:the research and experiment phase during the Eighth and the Tenth Five-Year Plan periods;the construction and operation phase during the Eleventh and the Thirteenth Five-Year Plan periods.This paper regards the Beijing-Shanghai High-Speed Railway as the corner stone in the development of high-speed railway subgrade system,and proposes suggestions and solutions to the problems which may reduce the service life of subgrade.These solutions and methods can be referred to in future railway projects.
