全风化花岗岩管沟回填土坡面侵蚀影响因素及交互作用

Influence Factors and Interaction of Slope Erosion of Completely Weathered Granite Pipe Trench Backfill

为了查明全风化花岗岩地区输油气管道作业边坡坡面水土流失问题,通过野外典型边坡边界条件测量、坡面侵蚀特征冲沟沟深、冲沟截面积数据采集、岩土体取样测试,并结合室内模型降雨试验等方法。结果表明:降雨、坡长、坡度、汇水面积、岩土体特性5种因素均影响全风化花岗岩管沟回填土坡面侵蚀。产沙率和产流率随着降雨强度的增大而增大。坡长、坡度、汇水面积与冲沟沟深和冲沟截面积呈正相关关系,且随着坡长、坡度、汇水面积的增大,冲沟沟深和冲沟截面积也在增大。通过取样测试发现,原状土与回填土的颗粒组成相对含量具有较大差异,初始回填土粒度级配为良好土。降雨冲刷初期回填土坡面径流主要携带粉粒和黏粒。5年回填土相对于原状土,孔隙率增加到原来的1.13倍,土体渗透系数增大1个数量级,饱和状态下黏聚力降低为原状土的67.6%,内摩擦角降低为原状土的87.5%。通过查明全风化花岗岩管沟回填土坡面侵蚀影响因素及其作用,为后续的边坡治理提供依据。

In order to find out the problem of soil and water loss on the slope side of oil and gas pipeline operation in fully weathered granite area,this paper adopted the methods of measuring the boundary conditions of typical slopes in the field,collecting the data of gully depth and gully sectional area of slope erosion characteristics,sampling and testing rock and soil mass,and the indoor model rainfall test.The results showed that rainfall,slope length,slope,catchment area and geotechnical characteristics all affected the slope erosion of backfill soil in fully weathered granite pipe trench.Sediment yield and flow yield increased with the increase of rainfall intensity.The slope length,slope and catchment area were positively correlated with gully depth and gully cross-sectional area,and the gully depth and gully cross-sectional area increased with the increase of slope length,slope and catchment area.Through sampling,it was found that the relative content of particle composition of undisturbed soil was different from that of backfill soil,and the particle size distribution of the initial backfill soil was good.At the initial stage of rainfall scouring,the runoff of backfill slope mainly carried away silt and clay particles.Compared with the original soil,the porosity of the backfill soil in five years increased to 1.13 times,the soil permeability coefficient increased by one order of magnitude,and the cohesion in saturated state and internal friction angle decreased to 67.6%and 87.5%of that of the original soil,respectively.By finding out the influencing factors and their effects on slope erosion of backfill soil in fully weathered granite pipe trench,it could provide a basis for the subsequent slope treatment.