长大隧道建设与运营安全致灾风险评估综述

随着我国长大、特大隧道不断涌现,隧道工程建设高速发展,而隧道风险评估领域研究稍显滞后,影响精品化隧道工程与高质量发展。对国内外长大隧道建设与运营阶段风险评估现状开展综述研究,从单因素评价法到多因素评价法对风险评估方法进行介绍及优缺点评价,并针对隧道建设阶段涌水、塌方、岩爆等风险,阐述单因素风险评估现状。同时介绍目前主要的风险评估方法,包括(模糊)层次分析法、贝叶斯网络法、神经网络法,并对不同方法进行简要评价。最后,就目前隧道领域风险评估进行总结,对该领域未来发展提供建议,以期为该领域工程和研究人员提供一定参考。

基于Chebyshev-Galerkin-KL展开的土质边坡稳定可靠度分析

提出了一种基于Chebyshev-Galerkin-KL(Karhunen-Loève)展开的新型随机场离散方法,推导了该方法的理论公式,并研发了基于Python语言的边坡滑体体积计算及其失效模式自动识别的高效程序。采用一个水位上涨时的非饱和土坡算例验证了方法的有效性。结果表明:所提随机场生成方法为求解第二类Fredholm积分方程提供了一种新思路,可准确表征岩土体参数的空间变异性。基于Python提出的边坡风险评估程序,与随机有限元计算过程不耦合,极大地提升了开展边坡风险评估的效率,从而增强预测滑坡致灾风险的时效性。此外,研究中非饱和土坡算例可靠度分析结果表明:水位上涨速度越慢,最大水位高度越高,该边坡的安全程度将越低。岩土体参数的竖向空间变异性对该算例边坡安全系数的影响甚微,但对滑体体积的影响较为显著。在对水位上升条件下的边坡开展可靠度分析时,应关注抗剪强度参数间的负相关性,否则将会低估边坡的安全程度。

地震边坡稳定性有限元塑性极限分析拟动力法研究

地震诱发边坡失稳是地震灾害的主要类型之一,开展地震作用下边坡稳定性研究具有重要意义。常规拟静力法无法准确模拟地震波在边坡土体中传播的时间和空间效应,难以真实反映地震荷载。本文采用拟动力法模拟地震动荷载输入,基于塑性极限分析下限定理,结合有限元离散技术,建立了满足静力平衡条件、屈服条件、应力边界条件和间断条件的地震边坡稳定性有限元极限分析下限法数学规划模型,基于内点算法寻求边坡超载系数和安全系数的下限解。通过对典型边坡算例分析,验证了本文方法的正确性。进一步分析了均质土边坡、抗剪强度参数随深度线性增加的非均质土边坡以及双层土边坡的地震稳定性,讨论了关联和非关联流动准则对地震边坡稳定性的影响。结果表明:拟静力法和非关联流动法则会低估地震边坡稳定性;边坡安全系数有限元极限分析下限解与上限解之间的差异小于4.5%,本文方法计算结果接近地震边坡稳定性真解。

Limit analysis of roof collapse in tunnels under seepage forces condition with three-dimensional failure mechanism

The state of roof collapse in tunnels is actually three-dimensional, so constructing a three-dimensional failure collapse mechanism is crucial so as to reflect the realistic collapsing scopes more reasonably. According to Hoek-Brown failure criterion and the upper bound theorem of limit analysis, the solution for describing the shape of roof collapse in circular or rectangular tunnels subjected to seepage forces is derived by virtue of variational calculation. The seepage forces calculated from the gradient of excess pore pressure distribution are taken as external loading in the limit analysis, and it is of great convenience to compute the pore pressure with pore pressure coefficient. Consequently, the effect of seepage forces is taken as a work rate of external force and incorporated into the upper bound limit analysis. The numerical results of collapse dimensions with different rock parameters show great validity and agreement by comparing with the results of that with two-dimensional failure mechanism.

交叉口服务水平的调查研究

交叉口是保证车辆与行人在交叉口能以最短的时间通过,使交叉口的通行能力适应各条道路的行车要求,因此对交叉口的通行能力及服务水平分析尤其重要。通过对瑞达路与化工路交叉口的调查取证及数据研究,运用层次分析法评价现阶段此交叉口的服务水平良好。最后采用神经网络对此交叉口进行了10年后交通量的预测。其交通量估计将达到6335辆,从而将导致此交叉口服务水平降低,影响车流安全顺畅运行,对此本文提出了一些建议。

Limit analysis of supporting pressure in tunnels with regard to surface settlement

The proliferation of Hoek-Brown nonlinear failure criterion and upper bound theorem makes it possible to evaluate the stability of circular tunnels with an original curved collapsing mechanism. The arch effect of shallow circle tunnel is not taken into consideration so that the mechanical characteristics can be easily described. Based on the mechanism, the upper bound solution of supporting pressure of tunnels under the condition of surface settlements and overloads on the ground surface is derived. The objective function is formed from virtual work equations under the variational principle, and solutions are presented by the optimum theory. Comparisons with previous works are made. The numerical results of the present method show great agreement with those of existing ones. With regard to the surface settlement and overloads, the influence of different rock parameters on the collapsing shape is analyzed.

Upper bound limit analysis of roof collapse in shallow tunnels with arbitrary cross sections under condition of seepage force

The analytical solutions for predicting the exact shape of collapse mechanisms in shallow tunnels with arbitrary excavation profiles were obtained by virtue of the upper bound theorem of limit analysis and variation principle according to Hoek-Brown failure criterion. The seepage force was included in the upper bound limit analysis, and it was computed from the gradient of excess pore pressure distribution. The seepage was regarded as a work rate of external force. The numerical results of roof collapse in square and circular tunnels with different rock parameters were derived and discussed, which proves to be valid in comparison with the previous work. The influences of different parameters on the shape of collapsing blocks were also discussed.

土工网加固的曲线型陡坡在地震区的机动性分析（英文）

本文采用机动分析法评估了陡坡在地震条件下维持其稳定所需土工网加固力。由于涉及复杂计算,已有文献在理论推导中主要考虑平面型边坡。而针对自然边坡中广泛存在着的曲线型边坡,尤其是地震作用下曲线型非均质边坡,传统的上限分析法难以考虑其稳定性。为了解决上述问题,本文首先采用离散技术生成一个离散的破坏机制,即将整个破坏块体分解成不同的组成部分,然后通过单元分析来计算土工网加固力及地震荷载等外部荷载所做功率和内能耗散,其中采用拟动力法来表示随时间和空间变化的横向和纵向加速度。最后,通过功率平衡方程获得土工网加固力上限解,并阐释了各因素对土工网加固陡坡性能的影响。

Stability analysis for natural slope by kinematical approach

The stability of natural slope was analyzed on the basis of limit analysis. The sliding model of a kind of natural slope was presented. A new kinematically admissible velocity field for the new sliding model was constructed. The stability factor formulation by the upper bound theorem leads to a classical nonlinear programming problem, when the external work rate and internal energy dissipation were solved, and the constraint condition of the programming problem was given. The upper bound optimization problem can be solved efficiently by applying a nonlinear SQP algorithm, and stability factor was obtained, which agrees well with previous achievements.