长输管道黄土暗穴影响分析

发布时间：2018-08-06 20:02

【摘要】：输气管道在不良地质环境下,表现出的潜在危险性已经引起了人们的注意,管道中输送的易燃、易爆介质,在管道破损后存在着极高的潜在危害。为此,在黄土地区,研究黄土暗穴对管道的影响具有重要的理论意义和实用价值。本文针对西气东输二线DL069潼关段,讨论研究区的地质条件、环境条件、管周黄土暗穴特征、发育规律及成因。采用现场调查、勘探、室内外试验及理论计算与数值模拟分析,对管周黄土暗穴的发育规律、成因机制及管道的受力关系进行分析,得到一些有价值的结果与结论。(1)基于研究区管周黄土暗穴发育特征,提出了管周黄土暗穴发育原因,包括(a)内因(土性条件、节理裂隙、地下水);(b)外因(回填土、降雨、植被覆盖率及防排水构筑物)。提出了管周黄土暗穴“回填土沉陷-管底土流失”形成机理。大致可以概括为“回填土沉陷——沉陷负地形聚水——沉陷裂隙形成——径流水沿着沉陷裂隙下渗——管道顶部陷穴形成——管土接触间隙增大——管底土流失——管周黄土暗穴形成”。(2)建立管道与管周黄土的流固耦合模型,探究了在降雨模式下,地表径流下渗时,管道与管周黄土关键部位的应力、应变的变化特点。得到管壁应力大于管底应力。应变由管中心向两边递减,但在回填土与原状土的交界处最大,这说明在原状土与回填土的交界处,接触间隙是导致水流下渗形成陷穴的主要通道。阐释了管周黄土暗穴的形成机制。(3)分析管道上覆土荷载、内部压力及温差应力。基于管土作用机制,建立无固定端单跨管道模型。假设管道(型号X80级),管顶埋深2m,通过理论计算,得到管道极限安全跨度为37m,可为西气东输管道的后期维护提供借鉴。
[Abstract]:Under the bad geological environment, the potential danger of gas pipeline has attracted people's attention. The flammable and explosive medium transported in the pipeline has a high potential harm after the pipeline is damaged. Therefore, it is of great theoretical and practical value to study the influence of hidden loess caverns on pipelines in loess region. In this paper, the geological conditions, environmental conditions, characteristics of loess underground caverns around Guanzhou, development rules and causes of the study area are discussed in view of the DL069 Tongguan section of West to East Gas Transmission Line 2. By means of field investigation, exploration, indoor and outdoor tests, theoretical calculation and numerical simulation analysis, this paper analyzes the development law, genetic mechanism and stress relationship of the loess underground caverns around the pipe. Some valuable results and conclusions are obtained. (1) based on the characteristics of the development of loess underground caverns around the pipe in the study area, the reasons for the development of the loess underground caverns around the pipe are put forward, including the internal causes of (a) (soil conditions, joints and fissures,); (b) external causes of groundwater (backfill, rainfall), etc. Vegetation coverage and waterproofing and drainage structures) The formation mechanism of "backfill soil subsidence-pipe subsoil loss" in loess hidden caverns around pipe is put forward. It can be summarized as follows: "backfill subsidence --subsidence negative topography accumulation -subsidence fissure formation -runoff water infiltration along the subsidence fissures-formation of caverns at the top of the pipeline-increase of tube-soil contact gap-loss of subsoil in the pipe The formation of underground holes in the loess around the pipe. (2) the fluid-solid coupling model between the pipeline and the loess around the pipe is established. The variation characteristics of stress and strain in the key part of loess around pipeline and pipe were studied under rainfall model and surface runoff infiltration. The results show that the wall stress is greater than the bottom stress. The strain decreases from the center of the pipe to the two sides, but the maximum is at the junction between the backfill and the undisturbed soil, which indicates that the contact gap is the main channel leading to the infiltration of the water flow to form caverns at the junction of the backfill and the backfill. The formation mechanism of loess caverns around the pipe is explained. (3) the soil load, internal pressure and temperature difference stress on the pipe are analyzed. Based on the action mechanism of pipe and soil, a single span pipe model without fixed end is established. Assuming that the pipe (type X80 grade) is buried at the top of the pipe at a depth of 2 m, the ultimate safety span of the pipeline is 37 m through theoretical calculation, which can be used for reference in the later maintenance of the West-East Gas Pipeline.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE973

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