排序方式: 共有61条查询结果,搜索用时 15 毫秒
51.
For shallow tunnels of single-lane railway and four-lane road,numerical simulation using finite differential code was conducted.The mechanical behavior of loose rock masses was studied considering the influences of shear dilation on the shape of the failure surface for the shallow tunnels,and the break angles using numerical simulation was compared with those using the Rankine’s analytical solutions and design code.From the comparisons,it is found that the difference between the break angle by numerical simulation and the design code is small when the shear dilation angle is equal to 0,with the maximum relative difference being less than 0.2% in road tunnels.With the dilation angle’s increase,the loose plasticity zone area of surrounding rock reduces obviously,and the break angle increases gradually.When the dilation angle is equal to the internal friction angle,the materials follow associated flow rule,and the numerical solution of the break angle is larger than the analytical solution,with the maximum relative difference being greater than 16.7% in road tunnels.Therefore,associated flow rule leads to overestimating break angle,and the dilation angle has an important influence on the failure surface shape for shallow tunnels in the loose surrounding rocks. 相似文献
52.
Influences of strain softening and seepage on elastic and plastic solutions of circular openings in nonlinear rock masses 总被引:2,自引:2,他引:0
Considering the influence of strain softening, the solutions of stress, displacement, plastic softening region radius and plastic residual region radius were derived for circular openings in nonlinear rock masses subjected to seepage. The radial stress distribution curve, ground reaction curve, and relation curve between plastic softening region radius and supporting force in three different conditions were drawn respectively. From the comparisons among these results for different conditions, it is found that when the supporting force is the same, the displacement of tunnel wall considering both seepage and strain softening is 85.71% greater than that only considering seepage. The increase values of radial displacement at 0.95 m and plastic softening region radius at 6.6 m show that the seepage and strain softening have the most unfavorable effects on circular opening stability in strain softening rock masses. 相似文献
53.
Modified image analytical solutions for ground displacement using nonuniform convergence model 总被引:1,自引:1,他引:0
Based on the image theory,the analytical solutions of tunneling-induced ground displacement were derived in conjunction with the nonuniform convergence model.The reasonable value of Poisson ratio in the analytical solution was discussed.The ground settlement width parameter which could reflect the ground condition was introduced to modify the analytical solutions proposed above,and new analytical solutions were presented.To evaluate the validity of the present solutions using the nonuniform convergence mode... 相似文献
54.
Numerical simulation using finite differential code was conducted for the single line railway and four-lane road shallow tunnels subjected to unsymmetrical pressure. The mechanical behavior of weak rock mass was studied considering the influences of stress dilatancy on the failure mechanisms, and the results of numerical simulation were compared with the analytical solutions in specifications. The results show that the dilatancy angle has great influences on the surrounding rock displacement and the shape of failure face for the shallow tunnels. When the dilatancy angle equals zero, the failure face of the surrounding rock forms and extends to the ground surface. With the dilatancy angle increasing, the loose region decreases gradually, and failure surface discontinues. When the dilatancy angle equals the friction angle, the loose region is only distributed in a small range around the crown and sidewalls. On the side of smaller buried depth, the difference of break angle between numerical simulation and the code is less than 10% for single line railway tunnels with the dilatancy angle of zero. However, for the four-lane road tunnels, the difference reaches 20.8%. On the side of larger buried depth, the break angles are smaller than those by the code, the difference reaches 16.8% for single line railway tunnels, and 13.8% for four-lane road tunnels. With the dilatancy angle increasing, especially the dilatancy angle approximating to internal friction angle, it is on safe side to calculate the break angle using the analytical solution method of specifications. Therefore, the influence of stress dilatancy should be considered while determining the failure mechanisms of shallow tunnels subjected to unsymmetrical pressure in weak rocks. 相似文献
55.
条形基础下纤维加筋土地基承载力初探 总被引:1,自引:0,他引:1
在岩土问题分析中,一直采用莫尔一库伦强度理论,由于该理论适用单一材料、且不考虑中间主应力σ2的影响。因此本文采用统一强度理论求解纤维加筋土地基的承载力。 相似文献
56.
大多数关于主动土压力的计算都是基于线性摩尔库仑准则.然而,实际上几乎所有的土体材料均遵循非线性关系,线性只是其中一个特例.根据非线性破坏准则,运用拟静态法考虑地震作用,利用极限分析上限定理求得主动土压力上限解.通过切线法原理引进中间变量,对墙后土体建立相容速度场,根据外力功率与内部能量耗散率相等的原理求出土压力的目标函数与约束条件,最后采用序列二次规划算法对该问题进行优化,得出主动土压力的最大值.将结果与已有文献进行分析比较,证明了该方法的可靠性.数值分析结果显示:随着水平地震系数的增加,主动土压力有非线性增大的趋势;非线性系数对主动土压力也有明显影响. 相似文献
57.
58.
采用非线性破坏准则并结合非关联流动法则, 基于构建的对数螺旋破坏机制, 对深埋盾构隧道掌子面的稳定性进行了极限分析, 并推导了支护力的上限解。利用数值优化方法, 计算得到了特定参数下支护力的最优解。结果表明:剪胀系数和非线性系数对支护力和破坏机制有较大影响, 建议在实际工程中考虑岩土材料的非线性和非关联特性。 相似文献
59.
60.