Research On Curtain Crouting Technology Of Dam Foundation And Engineering Application For Deep Overburden

China's major river basin are distributed in deep overburden, which has a loose structure, lithology is not continuous, genetic type complex, uneven physical and mechanical properties, strong permeability and other characteristics. There are a series of scientific and technical problems in the construction of water conservancy and hydropower project in deep overburden, such as the geological characteristics of the soil and the dam project dam adaptability, dam hydro-geological structure and spatial distribution of relatively impermeable layer, the selectionof physical and mechanical parameters of the soiland permeability index, foundation seepage, dam deformation, impermeability stability and seismic liquefaction stability. At the same time, higher requirements should be put forward for technology, construction machinery, construction technology and other aspects of deep overburden dam construction. In this paper, with Xiabandi Water Control Project as an example, based on geological data of the dam area and field test data to determine the physical and mechanical parameters of rock and soil, to study the variation of the dam and the dam foundation seepage and displacement field by numerical analysis method, and with the monitoring data were compared and analyzed, summed up the key construction technology of deep overburden cutoff wall and curtain grouting. The main contents and conclusions are as follows:(1)Using the numerical analysis method to study the effects of blanket length, thickness and permeability parameters and vertical cut-off wall and grout curtain depth, thickness and permeability of the dam foundation seepage control effect parameters, the results showed that:The effect of upstream impervious blanket level increases with the length enhanced, but more than four times the dam or thickness of more than2m, seepage effect not significantly improved, while reducing its permeability enhancing effect lasts seepage. The Seepage effect of vertical seepage cutoff wall and curtain grouting is enhanced with the increase of its depth. Vertical seepage cutoff wall and curtain grouting effect increases with the depth increased, improving the penetration of vertical seepage gradient structure, reducing the penetration of the downstream slope gradient. Whether the structure is completely cut off vertical impermeable cover layer thickness increases impervious structure and lower permeability coefficient, no significant effect on seepage effect.(2)For the structural features of deep overburden dam "on the wall under the curtain", the upper part of the concrete cutoff wall, the lower the use of impervious curtain. The main number for the lower value of the analog impervious curtain optimization, optimization models to project the amount of impervious curtain as the objective function, foundation seepage and maximum hydraulic landing of constraints, the calculated results showed that:set4rows impervious curtain, curtain thickness of11.01m, the maximum hydraulic gradient of5.45and meet regulatory requirements, and the optimization results and the actual project is consistent.(3)For the case of different formations deep overburden staggered and situation appears mixeddo indoor grouting testfor different gradation of gravel and sand, analysis grout slurry spread of different formations and groutability and get grouting parameters corresponding layers of sand and gravel; through a water pressure test, analysis of each common filling sand and gravel permeability coefficient decreases, the effect of improved impermeability to analyze the stability of different osmotic pressure at higher head formation, the analysis of seepage curtain grouting demonstration.(4)Research on deep overburden drilling methods and solid wall grout slurry technology, to solve difficult problems about overburden drilling and easily collapse hole, development for newgrouting materials that are deep overburden construction and excellent physical and mechanical properties, optimize existing curtain grouting equipment and technology, raised a set of deep overburden curtain grouting technology for China's National Condition-Orifice closed cycle grouting method.(5)By analyzing the deep overburden dam seepage monitoring data, mastered the penetration law and impervious body operating conditions, seepage field-based monitoring results, the use of BP neural network inversion dam and seepage permeation parameters, and dam seepage field numerical simulation the results showed that:the normal water level conditions in different impervious bulk connections should be reinforced, in the downstream part of the drainage filter layer impermeable body should be set up to do, to avoid damage occurred, conditions upstream water level dips and internal concrete dam seepage line elevation greater impact, less impact on the downstream slope, impervious concrete cutoff wall and curtain with internal osmotic gradient reduced the water level dropped.