基于板梁状陡坡地基倾倒稳定性分析的G-B改进模型研究

Research of improved G-B model for toppling stability analysis of plate-shaped steep slope foundation

为研究板梁状陡坡地基的倾倒变形,引入G-B块体倾倒模型,并针对以往G-B模型及其改进模型的研究中存在的2个问题(即对坡顶荷载考虑为连续均布荷载,无法考虑荷载作用点位置影响的问题,以及以往方法采用强度参数折减,无法判断板梁状陡坡破坏模式的问题),经过公式推导提出改进的G-B传递系数分析模型。该模型全面考虑坡顶局部荷载、裂缝静水压力及水平地震力,可用于各种因素影响下的陡坡倾倒稳定分析。将改进模型应用至矮寨悬索桥吉首岸陡坡地基稳定性分析中,探讨基础荷载、静水压力等因素对吉首岸陡坡地基倾倒稳定性的影响,分析不同工况下陡坡地基的稳定性。根据各种因素对吉首岸陡坡地基稳定性影响机理,提出相应的防治措施。研究结果表明:比较工况二(暴雨)与工况一(非暴雨)地基稳定系数计算结果,得到暴雨条件使地基倾倒稳定系数降低49%,地基滑移稳定系数降低19%;比较工况三(暴雨+地震)与工况二(暴雨)地基稳定系数计算结果,得到地震条件使地基倾倒稳定系数降低48%,地基滑移稳定系数降低20%。可见暴雨及地震不利工况对陡坡地基倾倒稳定性的影响比滑移稳定性影响更大。工况三(暴雨+地震)与工况四(暴雨+地震+塔基荷载)稳定系数计算结果相同,说明设计塔位下的塔基荷载对陡坡地基倾倒稳定性没有影响,设计塔位恰当。施工监测结果表明该塔基岩体尚无明显位移,说明该模型具有一定的理论价值与工程指导价值。

In order to study the toppling deformation of slab beam steep slope foundation,the G-B block toppling model was introduced.In view of the two problems existing in the research of the previous G-B model and the improved model(i.e.,the load on the slope top is considered as a continuous uniform load,and the influence of the position of the load action point cannot be considered;the previous methods use strength parameter reduction,which can not judge the failure mode of plate beam steep slope),through formula derivation,an improved G-B transfer coefficient analysis model was proposed.The model comprehensively considered the local load on the top of the slope,crack hydrostatic pressure and horizontal seismic force,and could be used for the stability analysis of steep slope toppling under the influence of various factors.Then,the improved model was applied in Jishou Bank of Aizhai suspension bridge,the stability of Jishou bank steep slope foundation under different working conditions was analyzed,and the effects of foundation load,hydrostatic pressure and other factors on the toppling stability of steep slope foundation were discussed.Finally,according to the influence mechanism of various factors on the stability of Jishou bank steep slope foundation,the corresponding prevention measures were put forward.The results show that comparing the calculation results of foundation stability coefficient under Condition 2(rainstorm)with that under Condition 1(non-rainstorm),rainstorm conditions reduce the foundation dumping stability coefficient by 49%and the foundation sliding stability coefficient by 19%.Comparing the calculation results of the foundation stability coefficient in combination Mode 3(rainstorm+earthquake)and combination Mode 2(rainstorm),the earthquake condition reduces the foundation dumping stability coefficient by 48%and the foundation sliding stability coefficient by 20%.The adverse conditions of rainstorm and earthquake have more influence on the stability of steep slope foundation than the sliding stability.The calculation results of the stability coefficient under Condition 3(rainstorm+earthquake)and Condition 4(rainstorm+earthquake+tower base load)are the same,indicating that the tower base load of the design tower location has no impact on the stability of the steep slope foundation,and the design tower location is appropriate.The monitoring results show that there is no obvious displacement of rock mass,which shows that the model has a certain theoretical and engineering guiding value.