Analysis And Research On Influencing Factors Of Slope Water Erosion In Longling Section Of China-Myanmar Oil And Gas Pipeline

Longling section of China-Myanmar oil and gas pipeline is mainly coarse-grained biotite granite distribution area,strong surface weathering,pipe ditch backfill is granite weathering residual sand,pipeline operation slope erosion is very serious.In the residual layer of granite after full weathering,the rock and soil structure is loose,accompanied by the development of a large number of joints and cracks,the mechanical properties are unstable,and it is easy to be washed by running water;the upper part of the pipeline is basically the clastic soil of the weathered layer,and the backfill soil is looser,which is very different from the original soil on the natural slope,and the surface layer is easy to be washed by running water.According to incomplete statistics,the pipeline passing through the fully weathered granite area is the most likely to cause slope water erosion(water damage)disaster.Therefore,it is necessary to study the mechanism of water erosion on slope in fully weathered granite area.In this experiment,taking the fully weathered granite area passed by Longling oil and gas pipeline as the research object,the erosion simulation experiments of 220mm/h rainfall intensity under four slopes(10 �,20 �,30 �and 40 �)were carried out by using two kinds of soil grooves(3m�1m�0.5m,3m�0.5m� 0.5m),and the erosion mechanism of residual sand in fully weathered granite area was studied.(1)the relationship between erosion mechanism and slope.In the process of rainfall,the slope has a strong influence on the rainfall infiltration,with the increase of the slope,the less the time needed for rainfall infiltration,the higher the infiltration rate.Therefore,for the low gentle slope,the erosion effect of rainfall is obviously lower than that of the high slope,and when the slope is between 20 �and 30 �,the amount of erosion will increase obviously.(2)the relationship between erosion mechanism and location.In the process of rainfall,it always takes more time for the foot of the slope to infiltrate than the top of the slope.under the same rainfall conditions,because Rain Water moves downward along the slope,the infiltration rate of the foot of the slope will be higher than that of the top of the slope.From the monitoring data of moisture content on the surface of the slope,it is obvious that the time for the soil at the top of the slope to reach saturation at the 10 cm depth is later than that at the foot of the slope,about 1-1.5 hours.And the position where the shallow trench is formed on the slope is often at the foot of the slope,and the position where the erosion ditch begins to be formed is often in the middle of the slope.(3)the relationship between erosion mechanism and slope velocity.In the process of rainfall,the slope has a strong influence on the flow velocity of runoff on the slope.with the increase of the slope,the velocity will increase and the erosion will be enhanced.For the slope of the same slope,the greater the intensity of rain,the greater the velocity of slope flow,the more prone to erosion.For different slopes,there is a positive correlation between slope velocity and slope.the smaller the slope is,the smaller the slope flow velocity is,but the infiltration will increase,so the change of erosion within 10 �is not obvious,but when the slope exceeds 10 �,the effect of flow velocity on erosion will increase obviously.