锚杆（索）挡土墙系统可靠性分析计算方法

发布时间：2018-06-08 00:54

本文选题：土压力 + 锚杆挡土墙　；参考：《湖南大学》2013年博士论文

【摘要】：锚固边坡中存在的不确定性因素多且复杂，故利用中值安全系数的传统方法来设计或分析锚固边坡，既不能较好地体现问题的复杂性与不确定性，也不能准确地评价工程的长期稳定性，应引入考虑荷载及抗力时变性且以概率统计理论为基础的分析设计方法。为此，本文结合国家自然科学基金(50878082)、交通部西部项目(200631880237)，考虑锚固计算参数和岩土体参数的统计特性，以锚杆挡土墙为主要研究对象，建立其系统时变可靠性分析模型与计算方法。主要研究内容和成果如下： (1)假定墙后填土的滑裂面曲线为通过墙踵的对数螺线函数，根据能量原理，推导出了墙面及填土面倾斜、墙面粗糙，既适用于砂性土又适用于粘性土的主动土压力上限解，并引入采用基于自然选择的改进粒子群算法对最危险滑裂面进行全局搜索。将本文解与砂性土土压力系数的经典上限解进行详细对比，发现当墙面倾角较小时两者差别甚微，但当墙面倾角大于30°时，经典上限解则明显偏小，而本文解与基于最优性原理的极限平衡解较接近。 (2)分别从是否考虑锚杆失效顺序的影响两个方面对板肋式锚杆挡墙的系统可靠性进行了分析。不考虑锚杆失效顺序时，以肋柱上的所有锚杆抗力之和作为系统锚杆的总抗力来建立极限状态方程。考虑锚杆失效顺序的影响时，将肋柱视为连续梁，锚杆视为弹性支座，引人锚杆与锚固段周围岩土体的复合刚度系数，用位移法导出各根锚杆所受荷载的统一计算公式。同时也考虑了锚杆的多种失效模式以及各种失效模式之间的相关性，提出了单根锚杆三种破坏模式串联系统与多根锚杆并联系统的系统可靠性分析方法和步骤，并编制了计算程序。 (3)将框架梁张拉阶段破坏和工作阶段纵梁与横梁的破坏，梁的正截面与斜截面的破坏以及锚杆的破坏等主要失效模式视为串联系统，提出了双梁双柱型框架预应力锚索的系统可靠性分析模型。然后基于各失效模式功能函数之间的相关系数矩阵，导出了其系统可靠性计算方法并编制了计算程序。 (4)基于矩阵位移法建立了框架预应力锚索挡墙在土压力荷载下的内力计算模型并编制了计算程序。视锚杆的失效为脆性破坏与延性破坏的中间状态，分别按脆性破坏与延性破坏计算锚杆体系失效概率的上下限。对工程实例的计算结果表明，若将锚杆视为脆性结构，当其中一根锚杆破坏后其邻近锚杆失效概率迅速增加，验证了脆性构件组成的超静定结构可视为串联系统；然后基于各根锚杆功能函数之间的相关系数矩阵，得到了脆性破坏时锚杆体系失效概率的上限；最后以立柱上所有锚杆同时达到极限状态的理想状态构建锚杆体系延性破坏时的功能函数，得到了其失效概率的下限。 (5)提出了按全概率法对边坡锚杆进行设计的思路。考虑到验算点法求可靠指标需要迭代计算，不能根据目标可靠指标直接求得设计参数，提出了基于二分法全概率设计的计算流程，一般只需几次迭代就能寻找到目标可靠指标下的设计参数。构建了基于可靠性锚杆挡墙优化设计模型，并运用粒子群智能优化算法对该模型进行优化计算。 (6)根据已有研究成果和工程经验假定土体抗剪强度参数及锚杆抗力随时间的衰减函数形式，，同时引入统一强度理论，得到了考虑中主应力系数的锚杆挡墙时变可靠性分析模型。据此模型编制程序对一土质边坡锚杆挡墙进行分析，发现时变性比统一强度理论对计算结果的影响更大。
[Abstract]:There are many uncertain factors in the anchorage slope, so the traditional method of median safety factor is used to design or analyze the anchored slope, which can not only reflect the complexity and uncertainty of the problem, but also can not accurately evaluate the long-term stability of the project. It should be introduced to consider the time variation of load and resistance and the theory of probability and statistics. Based on the National Natural Science Foundation (50878082) and the Western Ministry of communications project (200631880237), this paper considers the anchoring calculation parameters and the statistical characteristics of rock and soil parameters, and sets up the system time variable reliability analysis model and calculation method for the anchor retaining wall. The results are as follows:
(1) the sliding surface curve of the backfill of the wall is assumed to be a logarithmic spiral function through the heel of the wall. According to the principle of energy, the slope and the fill surface are incline and the wall surface is rough. It is applicable to the upper limit solution of the active earth pressure, which is applicable to the sandy soil and the cohesive soil, and introduces the improved particle swarm optimization algorithm based on the self selection for the most dangerous sliding surface. The global search is compared with the classical upper limit solution of the sand soil pressure coefficient. It is found that the difference between the wall angle and the wall angle is very small, but when the wall angle is more than 30 degrees, the classical upper bound solution is obviously smaller, and the solution in this paper is close to the limit equilibrium solution based on the principle of optimality.
(2) the system reliability of the ribbed bolt retaining wall is analyzed from two aspects of whether the effect of the bolt failure sequence is considered. When the failure sequence of the bolt is considered, the ultimate state equation is established by the sum of all bolt resistance on the rib column as the total resistance of the system bolt. Considering the effect of the bolt failure sequence, the rib column is considered. For continuous beams, the bolt is regarded as the elastic support, the composite stiffness coefficient of rock and soil around the anchor and anchorage section is introduced. The unified calculation formula for the load of each bolt is derived by the displacement method. At the same time, the various failure modes of the bolt and the correlation between various failure modes are also considered. Three types of failure modes of single bolt are put forward. System reliability analysis methods and steps of parallel system with multiple anchor rods are developed, and the calculation program is worked out.
(3) the system reliability analysis model of the double beam double column frame prestressed anchor cable is put forward, based on the phase between the failure modes and the failure modes of the frame beams and the failure modes of the longitudinal beams and beams, the failure of the cross section and the failure of the anchors and the failure of the bolt. The relation matrix is derived, and the calculation method of system reliability is derived.
(4) based on the matrix displacement method, the internal force calculation model of the prestressed anchor cable retaining wall under soil pressure is established and the calculation program is compiled. The failure of the anchor bolt is the middle state of the brittle failure and the ductile failure. The calculation knot of the engineering example is calculated according to the brittleness failure and the ductile failure. The results show that if the bolt is considered as a brittle structure, the failure probability of adjacent bolt increases rapidly when one of the bolts are destroyed, and it is verified that the statically indeterminate structure composed of brittle members can be considered as a series system, and then the failure probability of the bolt system is obtained on the basis of the correlation coefficient matrix between the functional functions of each bolt. In the end, the function function of the bolt system's ductility failure is constructed with the ideal state of all bolt on the column at the same time, and the lower limit of the failure probability is obtained.
(5) the idea of designing the slope bolt according to the full probability method is put forward. Considering that the reliability index of the checking calculation point method needs iterative calculation, the design parameters can not be obtained directly according to the reliable target of the target. The calculation process based on the full probability design based on the dichotomy is put forward, and the design of the target reliability index can be found only a few iterations. Parameters. An optimization design model based on reliability bolt retaining wall is built, and particle swarm optimization algorithm is applied to optimize the model.
(6) according to the existing research results and engineering experience, the shear strength parameters of soil soil and the attenuation function of anchor resistance with time are assumed. At the same time, the unified strength theory is introduced to obtain the time-varying reliability analysis model of anchor retaining wall considering the central stress coefficient. The time variant is more influential than the unified strength theory on the calculation results.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU476.4

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