Research On The Assessment Of Construction Risk In The Accumulation Landslide Area Along The China-Myanmar Oil And Gas Pipeline

The characteristics of long distance gas and oil transmission pipelines,such as widespread stations,long line and extensive coverage,decided that it is inevitable to be constructed in the area of landslide disaster.The construction accidents in landslide area at home and abroad show that the slope slide,induced by trench excavation,construction load,improper support,would result in loss of life and property.In order to prevent the occurrence of landslide disaster during pipeline construction,and provide the basis for disaster prevention and mitigation of the pipeline construction,the landslide disaster and pipeline construction behavior,based on the China-Myanmar oil and gas pipeline project,are setted as the research object,and following research work was carried out:(1)According to the statistical analysis of characteristics and development scale of the landslide disaster,the distribution law of the accumulation landslide along the pipeline was analyzed,and the development rule of the landslide induced by the pipeline construction was studied.(2)The WBS method was used to decompose the pipeline construction in the landslide disaster area into different stages and processes,and risk factors were identified by causality diagram from the aspects of human,machine,material,method and environment.(3)Through the finite element simulation,the function law of main risk factors in the pipeline construction affectting the accumulation landslides was probed.(4)Combined with the function law of main risk factors,the risk evaluation index system of pipeline construction was established.(5)The risk assessment method of pipeline engineering construction in the accumulation landslide disaster area by using Bayesian network and fuzzy comprehensive method was studied,and an example-the beautiful river landslide is given to verify the its correctness.Based on the above researches,the main conclusions are as follows:(1)Through the investigation and statistics of landslide disasters along the China-Burma oil and gas pipeline,it was found that the accumulation landslide and instability slope were in the highest proportion(68.5%),and thickness of accumulation layer between 0-3m accounting for 85.7%,and the largest distribution of bedrock is mud sandstone or the combination.In the 7 ways of piping and slope intersection,crossing slope toe has the highest proportion(44%).The development model of landslide induced by pipeline construction can be divided into three types:rapid excavation-shear and sliding model,load vibration-shear and sliding model,slow excavation and rainfall coupling model.(2)Through work breakdown structure(WBS)method,the project of pipeline construction in landslide disaster area was decomposed into preparation stage,anti sliding piles construction stage,drainage construction stage,slope monitoring stage,trench excavation and backfilling stage,grand total 5 construction stages and the corresponding 14 main construction procedure.By establishing cause and effect diagram of the construction environment risk and the 5 stages of construction risk,the main risk factors and the hierarchical relationship between them were identified.(3)The influence law of the main characteristic risk factors is analyzed quantitatively in the finite element numerical model,such conclusions were obtained:When slope height is more than 60m,or the slope angle more than 45 degrees,the control effect on the stability of slope is itself’s structure,and the influence of slope excavation trench on slope stability decrease.The slope toe excavation in pipeline construction reduces the slope stability,but exert construction load will enhance the stability of slope;excavation on slope middle and top position improves the stability of slope,and exert construction load will reduce of slope stability.When the embedded part length of anti slide piles reaches 1/3,or the pile body is arranged in the distance of excavation surface 10m～15m,pipe trench excavation risk is minimum.(4)According to the law of influence of characteristic factors,the construction risk probability evaluation index system is established,and the prior probability of each risk factor is given.By using the Bayesian network method,the construction environment and the construction stage risk probability model were established,which can achieved the forward and reverse derivation on the construction risk probability.The fuzzy comprehensive evaluation method is used to establish the evaluation index and evaluation method of construction risk loss in three aspects of life,property and environment.At last,the risk grade evaluation matrix,which comprehensively consider construction risk probability and construction risk loss,is established.(5)The pipeline construction in beautiful River landslide area was assessed by the above mentioned method,the overall construction risk probability was calculated 0.084931,which belongs to the "higher risk"grade,and the risk loss grade was evaluated"lighter",then comprehensive construction risk rating was gotten the "medium",which was coincidence with the construction site,and shows that the method is practical and correct.