滑坡时空演化规律及覆管力学响应研究

Study on temporal and spatial evolution law of landslide and mechanical response of overburden pipe

山体滑坡是威胁天然气管道安全运营的主要地质灾害,研究适应于滑坡演化规律及覆管力学响应状态的分析方法具有重要的工程意义。为此,首先采用坡体系统(阻滑段-下滑段)总势能平衡方程,即拉格朗日变分方程,并基于最小势能原理,获得坡体失稳滑移的临界条件——下滑段应变能释放量等于阻滑段破裂贯通所需要的应变能时,坡体即发生滑移,坡体内部储存的应变能转化为动能。一方面,根据滑动全过程中的岩土体颗粒与管道外壁接触关系,提出了滑坡两阶段的管道力学响应模式;另一方面,考虑岩土体颗粒的碎散度,分别构建岩质滑坡作用下管道的均匀受力模式及土质边坡管道的非均匀受力模式。鉴于此,从小尺度管土相互作用的力学响应出发,推导出岩质边坡与土质边坡滑动前后阶段的管道弹性部分受力表达式。最后,以川气东送EES244段天然气管道跨越滑坡为研究对象,建立了边坡系统总势能方程,分析出坡体的变形、失稳及滑移情况,计算出管道在不同滑动阶段的应力值,对管道的安全性进行了评价。同时,采用数值模拟的方法,从整体大尺度角度对全管段进行受力分析与安全性校核。结果表明:滑动区与未滑动区的交界面附近管道出现应力突变,滑动区内部应力小幅度增加,但整体处于安全稳定状态。因此,采用的小尺度理论计算与大尺度整体数值模拟的研究方法,对拟建管道前期设计、现役管道安全评价和后期管道维修等具有指导意义及实用价值。

Landslide is the main geological disaster that threatens the safe operation of natural gas pipelines.It is of great significance to investigate the analysis method that is suitable for the evolution law of landslide and the mechanical response of overburden pipes in engineering.Therefore,based on the principle of the minimum potential energy,the total potential energy balance equation of slope system(from anti-sliding section to sliding section),i.e.,the Lagrange variational equation,was firstly adopted to obtain the critical conditions for the instability and slip of the slope.When the strain energy of the sliding section is equal to the strain energy for the crack and penetration of the anti-sliding section,the slope will slip.Meanwhile,the strain energy stored in the slope will be transformed into kinetic energy.On one hand,according to the contact relationship between the rock mass and the pipeline during the sliding process,the mechanical response model of the pipeline in two landslide stages is proposed.On the other hand,considering the fragmentation of the rock and soil mass,the uniform stress model of pipeline under the action of rock landslide and the non-uniform stress model of soil slope pipeline are proposed respectively.In view of this,based on the mechanical response for the small-scale interaction of the pipeline and soil,the stress expression of the pipeline in the pre-and post-sliding stages of rock and soil slopes,which is suitable in the elastic part,is derived.Finally,taking the EES244 section of natural gas pipeline from Sichuan to East as the research target,the total potential energy equation of the slope system is established,the situations for deformation,instability and slip of the slope are analyzed,the stress values of the pipeline in different sliding stages are calculated,and the safety of the pipeline is evaluated.Meanwhile,the stress analysis and the safety verification of the pipeline are carried out from a large-scale perspective by means of the numerical method.The results show that a sudden change of stress in the pipeline will be occurred near the interface between the sliding zone and the non-sliding zone,and the internal stress in the sliding zone increases slightly,while the whole pipeline is in a safe and stable state.Therefore,combining the small-scale theoretical calculation and the large-scale numerical method is of great significance and practical value,especially for the preliminary designing of the proposed pipeline,the safety evaluation of the existing pipeline and the later maintenance of the pipeline.