复杂山区煤矿采空区油气管道稳定性监测与数值分析

In-Situ Monitoring and Numerical Analysis of Oil and Gas Pipelines in Coal Seam Goaf Located in Mountainous Terrain

煤矿采空区引起地表沉降和塌陷,威胁采空区上方油气管道的安全。采用数值模拟方法可以分析煤矿或油气采空区不同工况条件下油气管道的力学性状,采用管道附着式传感器可以监测管道应力状态,但两类方法并未开展耦合分析,无法通过实时分析管道自身与周围土体共同作用下的形变与应力,反演管道完整性与岩土围压环境,也无法实现对油气长输管道运行状态动态监测与管理。本文采用原位监测与数值模拟相结合的方法,对遵义双田煤矿采空区上方的成品油管道开展了管道本体稳定性研究。结果表明:在监测周期内,监测区域孔隙水压随着降雨量的增加而增大,但变化幅度较小;纵向位移整体呈增大趋势,但最大相对位移仅1.5 mm,地面沉降较小。基于原位监测进行数值模拟,得到的模拟结果与监测数据变化趋势相同,且模拟位移与监测位移变化范围相近,表明模拟结果较为准确。通过模拟结果分析,发现管道所受应力远小于临界值,推断管道处于稳定状态。但若煤矿处于开采状态,随着开采范围的增加,监测区域管道的轴向应力和剪应力急剧增大,当开挖范围超过40 m时,管道将处于失稳状态,极易发生破坏。本研究采用原位观测校核数值模拟结果的方法分析管道稳定性,基于该方法可指导穿越采空区油气管道的评估和预警工作。

Ground subsidence and collapse quite occurs in coal mine goaf,threatening the safety of oil-gas pipelines above the goaf.Although numerical simulation can be used to analyze the bearing behavior of oil-gas pipes under different loading cases in mined-out areas,and sensors attached to pipes are appliable to detect pipe stress state,there was not joint analysis available which combined the two methods.It was not advisable to estimate the integrity of oil-gas pipelines by analyzing the strain and stress of oil-gas pipe without inclusive of ambient geo-environment,such as overloading soil pressure,and further it also cannot realize the dynamic monitoring and management of the operation of long-distance oil-gas pipelines.In this paper,the stability of the oil-gas pipeline above the goaf of Shuangtian Coal Mine,Zunyi county,China was estimated by combining in-situ monitoring and numerical simulation.Results shows:(1)Within a monitoring cycle,the observed values of pore water pressure increased with the increase of rainfall,but their variation ranges were small;The longitudinal displacement tended to increase as a whole,with the maximum relative displacement only 1.5 mm,a small settlement.(2)The numerical simulation based on in-situ monitoring found a consistent change trend as compared with observation,for instance,the simulated displacement of ground subsidence similar to those from in-situ monitoring,suggesting that the simulation was reliable.(3)By simulation,it found that the stresses on a pipeline were far low than its critical value,referring to the pipelines in stable state;However,in case the coal mine was in the mining state,the axial stress and shear stress of the detected pipelines increased sharply with the increase of mining range;Once the excavation range exceeds 40 m,the pipeline came up to an unstable state and prone to damage.This study uses the method of checking numerical simulation with in-situ observations to analyze pipeline stability,which can guide the assessment and early warning of oil and gas pipelines crossing goaf.