Sichuan Basin Red Rock Permeability And The Control Of Water Conservancy Engineering

There is widespread red rock in Sichuan Basin and its marginal area. Total about 165 thousands km2 red rock is on the ground. In Sichuan Province, there is about 120 thousands km2 red rock which takes 25% of total Sichuan's area. Most of the red rock is Jurassic and Cretaceous layer. Its lithology is soft, attribute of geological engineering is weak. Because the water resource is uneven distribution on time and space in this area, there is a demand for building water conservancy engineering to regulate it. The geology problems of the built and building water conservancy engineering have gradually come out, and foundation leakage is one major question. Study on the permeability properties of Sichuan Basin's red rock is important for sustainable development of water conservancy engineering.Based on the topography, geological structure, sedimentation background, lithology, hydro-geological characteristics of Sichuan Basin Red Rock, divided Sichuan Basin to three zones: the northwest zone, the middle zone and the south zone. Relying on reconnaissance data of twenty-one water conservancy engineering, systematically read 4,300 group of data of 300 drilling holes, discussed mainly the controlling effect of four significantly correlated influencing factors of rock permeability properties: lithological factors, weathering factor, geological factors, easily dissolved component factors on permeability properties. Detailed analyzed the red rock permeability properties of each water conservancy engineering and engineering geological zone.The analysis shows that there's a certain regulation between rock permeability and the factors, and the rock permeability properties are different because of the difference of geological characteristics between the engineering geological zones. Through the research, following achievements have been made:(1) The lithological factor is the most important controlling factor of rock permeability properties. In fresh rock, the permeable rate of sandstone intercalated with mudrock is 8~12Lu, the permeable rate of mudrock intercalated with sandstone is 2~8Lu, the permeable rate of intercalation is 0~5Lu, the permeable rate of mudrock is 0~1Lu.(2) Influenced by weathering factor, the permeable rate of hard weathered rock is commonly more than 100Lu, the permeable rate of soft weathered rock is 5~100Lu, and the permeable rate of fresh rock is less than 10Lu.(3) Three types of soft intercalations born of tectonism which are on the drilling segment with different lithological combination have different permeable rate range. On the drilling segment with sandstone intercalated with mudrock, the permeable rate of inter-laminar dislocation band of rock cuttings is 10~53Lu, the permeable rate of inter-laminar dislocation band of rock cuttings intercalated with mud is 4~22Lu, the permeable rate of inter-laminar dislocation band of mud intercalated with rock cuttings is 2~4.25Lu. On the drilling segment with mudrock intercalated with sandstone, the permeable rate of inter-laminar dislocation band of rock cuttings is 6~29Lu, the permeable rate of inter-laminar dislocation band of rock cuttings intercalated with mud is 2.6~15Lu, the permeable rate of inter-laminar dislocation band of mud intercalated with rock cuttings is 1~4Lu. On the drilling segment with intercalation, the permeable rate of inter-laminar dislocation band of rock cuttings is 5~22Lu, the permeable rate of inter-laminar dislocation band of rock cuttings intercalated with mud is 1.5~13Lu, the permeable rate of inter-laminar dislocation band of mud intercalated with rock cuttings is 0.9~3.4Lu. On the drilling segment with mudrock, the permeable rate of inter-laminar dislocation band of rock cuttings is 2~15Lu, the permeable rate of inter-laminar dislocation band of rock cuttings intercalated with mud is 1.8~7Lu, the permeable rate of inter-laminar dislocation band of mud intercalated with rock cuttings is 0.25~1.4Lu.(4) The holes dissolved by easily dissolved component increase the discharge of groundwater. The content of easily dissolved component is proportional to rock permeable rate.(5) The lithological and soluble salt factors are main controlling factors in the northwest zone, the lithological and weathering factors are main controlling factors in the middle zone, the lithological and geological factors are main controlling factors in the south zone.(6) Establish finite element model of groundwater seepage to simulate the movement of groundwater. Concluded the pattern and the degree of influence of the possible range of rock permeability. Achieve the control of rock permeability to water conservancy engineering.