渗流和地震耦合作用下边坡稳定性分析

发布时间：2018-01-04 13:04

本文关键词：渗流和地震耦合作用下边坡稳定性分析　出处：《中国地震局工程力学研究所》2017年博士论文　论文类型：学位论文

【摘要】：地下水渗流和地震对边坡的稳定性都有重要影响,渗流和地震共同作用这一复杂工况下的边坡稳定性问题已成为当前岩土工程研究的热点问题之一。主要问题是渗流和地震共同作用时稳定性的计算方法需要探索和完善;各种影响因素需要深入分析和研究。本文的研究工作为解决复杂工况下的边坡稳定性分析和评价提供了一种新的思路,这一工作对多工况耦合作用下的边坡失稳机理研究和稳定性评价具有重要的理论参考和实际意义。本文在前人已有工作的基础上,基于极限平衡理论和数值模拟开展了渗流和地震两种工况耦合作用下的边坡稳定性分析和计算方法的研究;并对特殊类边坡的稳定性问题进行了分析和探讨,主要工作和成果如下:1、推导并给出了砂土边坡和粘土边坡在渗流和地震作用下安全系数的解析式;提出了水平积分模型的广义形式。相关算例结果对比表明,依赖严格几何条件和边界约束的解析法可以得到其它方法一致的结论,计算结果反映了安全系数随振动时间的变化规律,计算值要小于规范中的拟静力法结果,但与动力时程法结果基本相近,具有一定的可靠性。参数分析表明水力梯度和水位差对边坡稳定性的影响显著,特别是高水位差时边坡稳定性显著降低,水平方向地震力会严重削弱边坡的稳定程度,而竖向地震力对稳定性的影响要小于水平地震力的作用。本文通过数学积分得到了异形边坡水平积分模型的解析算式,结果表明,该方法计算的安全系数一般偏低,稳定性评价相对保守。采用解析方法得到的边坡安全系数对深入开展渗流和地震耦合作用下的边坡失稳机理的研究提供了重要理论基础,为进一步探索安全系数变化规律提供了有效工具。2、提出了以滑动面倾角为权重的整体安全系数评价方法,并以天津波作为输入地震动,结合点安全系数法分析了渗流和地震复杂工况下的边坡稳定性。本文取实际工程中的两台阶边坡为研究对象,讨论了渗流应力耦合作用对两台阶边坡应力场、位移场的影响以及平台宽度、边坡倾角等坡体参数对稳定性的影响。研究结果表明,修正后的整体安全系数要比传统的瑞典条分法给出的结果偏高,与有限元强度折减法所得的结果和前期勘察结论基本一致。渗流应力耦合作用对边坡的水平位移影响明显,对竖向位移影响较小,对具有强渗透性的砂土类边坡应重点考察耦合作用对应力场和位移场的影响,而平台宽度和边坡倾角是制约滑动面形状和位置的重要因素,同时说明了多阶边坡的剪出口不再唯一。本文的工作提示,应用点安全系数法分析边坡稳定性时,应尽量采用高阶单元、低网格划分、大尺度边界的计算原则,这样可以提高计算效率,降低计算成本。3、提出了坡顶裂缝最大取值的界定依据,分析了复杂工况下裂缝尖端的应力强度因子。本文研究结果表明,基于单轴最大拉应力理论和土体变形参数所得到的裂缝深度计算公式,可约束坡顶最大裂缝的取值。与极限平衡法相结合,可计算张拉剪切作用下的边坡安全系数,所得结果是安全系数的下限值,稳定性评价偏于保守。本文利用应力强度因子较好地解释了坡顶裂缝在侧向水压力和水平地震力作用下裂缝扩展的原因,并与数值模拟中裂缝尖端位置的应力集中基本一致。尽管本文的相关方法为拉剪复合破坏模式下的边坡稳定性分析提供了一种新思路,但方法的可靠性还需进一步检验。4、推导了软弱夹层自振频率的近似解,提出了含软弱夹层这类特殊边坡稳定性的简化计算方法及适用范围。研究结果表明,含软弱夹层边坡的失稳是由坡体与夹层的共同作用所导致。本文利用弹性力学中的能量法计算了软弱夹层的自振频率,通过与谐波共振结果对比,说明了软弱夹层在边坡失稳中的重要作用。基于极限平衡理论,以圆弧滑动占复合滑动的比值为权重,本文给出了含软弱夹层边坡稳定性的简化计算方法。相关算例结果对比表明,简化方法计算的安全系数一般偏小,并对软弱夹层厚度小、倾角小、水平分布在坡底的这一类边坡较为适用;对于夹层厚度较大的边坡,建议简化为本文中的成层土边坡进行分析。
[Abstract]:Have an important impact on the stability of groundwater seepage and earthquake on slope, the slope stability problem of the complicated interaction of seepage and earthquake has become one of the hot issues in the research of geotechnical engineering. The main problem is the interaction of seepage and earthquake stability calculation method to explore and perfect the in-depth analysis and study of factors; a variety of effects. The research work provides a new way to solve the slope stability analysis and evaluation of complex conditions, with theoretical reference and practical significance of this research and evaluation mechanism of losing stability on the slope stability condition under coupling. Based on the previous work, the research limit equilibrium theory and numerical simulation to carry out stability analysis of slope seepage and earthquake two conditions under the coupling effect and calculation method based on and on; Analyzed and discussed the stability problem of slope is the main work and results are as follows: 1. The analytic formula and safety coefficient are given in the sand slope and clay slope seepage and earthquake; proposed a generalized form integral level model. The numerical results show that the correlation ratio, analytic method relies on strict geometric conditions and boundary constraints can come to the conclusion that other methods consistent with the calculation results reflect the variation of safety coefficient with the vibration time, the calculated values to be pseudo static method result is less than the norm, but with the dynamic time history analysis results, has certain reliability. Parameter analysis shows that the hydraulic gradient and the water level difference effect on slope stability obviously, especially the high water level difference of slope stability decreased significantly, the horizontal seismic force will seriously undermine the stability of the slope, and the vertical seismic force on the stability. Ring is smaller than the horizontal seismic force. Through mathematical integral formula, special slope level integration model. The results show that the safety factor calculated by this method is generally low, the stability evaluation is relatively conservative. Provide the important theoretical basis of the study of slope safety coefficient obtained by the analytical method to carry out the slope seepage and earthquake the mechanism of instability, provides an effective tool for further exploration of.2 variation of safety factor, put forward the overall safety factor evaluation method of weight to the sliding surface inclination, and taking Tianjin wave as the input ground motion, seepage and earthquake under the complicated conditions of slope stability analysis with the point safety factor method. Two steps slope this paper takes the actual project as research object, discusses the seepage stress coupling stress of two steps slope field, displacement field and flat effect Table width, slope angle and slope parameters influence on the stability. The results show that the safety factor of the modified than traditional Fellenius method gives higher results, the conclusion and the strength reduction FEM results and preliminary investigation should be basically the same. The seepage influence on the horizontal displacement of slope stress. Obviously, has little effect on the vertical displacement, the strong permeability of sandy soil slope should investigate the coupling effects of stress field and displacement field, and the width of the platform and the slope angle is an important factor restricting the shape and position of the sliding surface, and indicates that the shear outlet of multi-step slope is no longer the only. This work suggests that the slope stability analysis, application of point safety factor method, should be used in high order element, low meshing, calculation principle of large scale boundary, so it can improve the computational efficiency, lower calculation The.3, put forward the definition according to the maximum value of slope crack, analyzes the stress intensity factors of crack under complicated working conditions. The results of this study indicate that the crack depth formula of uniaxial tensile theory and soil deformation parameters obtained based on the slope can constrain fracture combined with limit values. Balance method, can calculate the tension of slope safety factor under shear, the result is the lower limit of safety coefficient, stability evaluation on the conservative side. The stress intensity factor can explain the cause of crack in the lateral water pressure and horizontal seismic force of slope cracks, and is consistent with the stress concentration the crack tip position in numerical simulation. Although this method provides a new idea for slope stability analysis of composite shear failure modes, but the reliability of the method also need one Step.4 inspection is the approximate solution of weak interlayer vibration frequency, calculation method is put forward and the scope of this special kind of slope with weak interlayer stability is simplified. The results show that the slope with weak interlayer instability is caused by a combination of slope and interlayer. In this paper, the natural frequency of weak interlayer is calculated by using the energy method in elastic mechanics, by comparing with the harmonic resonance results shows that weak layers in the slope stability in an important role. Based on the theory of limit equilibrium, the circular sliding ratio of composite sliding as the weights are given in this paper with the simplified calculation method of slope stability of weak interlayer. Numerical results show that the contrast the safety coefficient is generally small, simplified calculating method, and the soft interlayer thickness is small, a small angle, the horizontal distribution is more applicable in this kind of slope slope; slope for large thickness, It is suggested to simplify the analysis of the layered soil slope in this paper.

【学位授予单位】：中国地震局工程力学研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TU43

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