深厚覆盖层坝基帷幕灌浆技术研究及工程应用

发布时间：2019-03-28 09:23

【摘要】：我国各大流域河床中都分布有深厚覆盖层,其具有结构松散、岩性不连续、成因类型复杂、物理力学性质不均匀、透水性较强等特性,在深厚覆盖层上修建水利水电工程存在一系列科学技术难题,如坝基土体的工程地质特性及建坝适应性、坝基水文地质结构和相对隔水层的空间分布、土体物理力学参数和抗渗指标的选取、坝基渗漏、坝基变形、抗渗稳定及抗震液化稳定等,与此同时,对于深厚覆盖层坝基施工技术、施工机械、施工工艺等方面也提出了更高的要求。本文以下坂地水利枢纽工程为例,基于坝址区地质资料和现场试验数据,确定了岩土体的物理力学参数,采用数值分析方法研究了坝体和坝基渗流场和位移场的变化规律,并与监测数据进行了对比分析,总结了深厚覆盖层防渗墙和帷幕灌浆关键施工技术。主要研究内容和结论如下所示： (1)采用数值分析方法研究了铺盖的长度、厚度和渗透参数以及垂直防渗墙和防渗帷幕的深度、厚度和渗透参数对坝基渗流控制效果的影响,结果表明：上游水平铺盖的防渗效果随其长度和厚度增加而增强,当水平长度超过4倍坝高或厚度超过2m时,防渗效果未有显著提高,而渗透系数降低时其防渗效果持续增强；垂直防渗墙和帷幕灌浆的防渗效果随其深度增加而增强,提高了垂直防渗体结构的渗透坡降,降低了下游坝坡的渗透坡降；无论垂直防渗结构是否完全截断覆盖层时,增加防渗结构厚度和降低渗透系数,对防渗效果无明显影响。 (2)针对深厚覆盖层坝基防渗体布置的特点——上部采用混凝土防渗墙,下部采用防渗帷幕,本次数值模拟主要针对下部防渗帷幕进行优化,优化模型以防渗帷幕的工程量为目标函数,坝基渗流量和最大水力迫降为约束条件,计算结果表明：设置4排防渗帷幕,帷幕厚度为11.01m,最大水力坡降为5.45,满足现行规范要求,并且优化结果与实际工程帷幕排数一致。 (3)针对深厚覆盖层不同地层交错、混合出现的情况,对不同级配的砂砾石和细砂进行室内灌浆试验,分析灌浆浆液在不同地层的扩散情况和可灌性,并获取相应砂砾石层的灌浆参数；通过压水试验,分析灌浆对各常见砂砾石地层渗透系数减小、抗渗性能提高的效果,分析在较高水头压力作用下不同地层的渗透稳定性,对防渗帷幕灌浆进行分析论证。 (4)研究深厚覆盖层灌浆钻孔方法和固壁泥浆技术,解决覆盖层钻孔难、易塌孔的难题；开发适合深厚覆盖层施工且物理力学性能优异的灌浆新材料;优化现有帷幕灌浆施工设备和工艺,提出一套适合中国国情的深厚覆盖层帷幕灌浆施工技术——孔口封闭循环灌浆法。 (5)通过分析深厚覆盖层坝基渗流监测数据,掌握了渗透规律及防渗体运行状况；基于渗流场监测成果,采用BP神经网络反演坝基和防渗体渗透参数,并对坝基渗流场进行了数值模拟,结果表明：正常蓄水位工况下在不同防渗体相连接处应进行加固,在防渗体下游排水部位应做好反滤层设置,避免发生破坏；库水位骤降工况下上游坝坡和混凝土内部浸润线高程影响较大,对下游坝坡影响较小,混凝土防渗墙和防渗帷幕内部渗透坡降随库水位下降而降低。
[Abstract]:In that river bed of the major valley of China, there are deep overburden, which have the characteristics of loose structure, discontinuous lithology, complex genetic type, non-uniform physical and mechanical property, strong water permeability, etc., and a series of scientific and technological problems exist in the construction of water conservancy and hydropower project on the deep cover layer. such as the engineering geological characteristics of the soil body of the dam foundation, the adaptability of the dam, the hydrogeologic structure of the dam foundation and the spatial distribution of the relative water-insulating layer, the physical and mechanical parameters of the soil body and the selection of the anti-permeability index, the seepage of the dam foundation, the deformation of the dam foundation, the anti-seepage stability and the anti-seismic liquefaction stability and the like, The construction technology, construction machinery, construction technology and other aspects of the deep covering layer dam foundation have also put forward the higher requirements. Based on the geological data and the field test data of the dam site area, the physical and mechanical parameters of the rock and soil body are determined based on the geological data of the dam site area and the on-site test data. The law of the seepage field and the displacement field of the dam body and the dam foundation is studied by means of the numerical analysis method, and the comparison and analysis with the monitoring data are carried out. The key construction technology of the thick-layer cut-off wall and curtain grouting is summarized. The main contents and conclusions are as follows: (1) The influence of the length, thickness and penetration parameters of the cover and the depth, thickness and penetration parameters of the vertical cut-off wall and the anti-seepage curtain on the seepage control effect of the dam foundation are studied by means of the numerical analysis method. It is clear that the anti-seepage effect of the upstream horizontal cover is enhanced with the increase of its length and thickness, and when the horizontal length exceeds 4 times the dam height or the thickness is over 2 m, the anti-seepage effect is not significantly improved, and the seepage-proof effect of the upstream horizontal spreading cover is continuously increased when the permeability coefficient is reduced. The anti-seepage effect of the vertical anti-seepage wall and the curtain grouting is enhanced along with the increase of the depth, the seepage slope of the vertical anti-seepage body structure is improved, the seepage slope of the downstream dam slope is reduced, No obvious shadow on the anti-seepage effect. In response to (2) the characteristics of the anti-seepage body layout for the deep cover layer dam foundation, the upper part adopts the concrete anti-seepage wall and the lower part adopts the anti-seepage curtain. The numerical simulation mainly aims at the optimization of the lower anti-seepage curtain, and the optimization model is based on the engineering quantity of the anti-seepage curtain. The calculation results show that:4 rows of anti-seepage curtain are set, the curtain thickness is 11.0m, the maximum hydraulic pressure drop is 5.45, the current specification requirements are met, and the result of optimization and the actual project curtain row are optimized. and (3) carrying out indoor grouting test on the sand-gravel and the fine sand with different grades aiming at the condition that the deep covering layer is staggered and mixed in different layers, and analyzing the diffusion condition and the filling property of the grouting slurry in different layers, and obtaining the grouting parameters of the corresponding sand-gravel layer; and the method comprises the following steps of: Through the water pressure test, the effect of grouting on the permeability coefficient of each common sand and gravel formation and the improvement of the anti-seepage performance is analyzed, and the seepage stability of different strata under the action of higher head pressure is analyzed, and the grouting of the anti-seepage curtain is carried out. Line analysis and demonstration. (4) To study the deep-layer grouting drilling method and the solid-wall mud technique, to solve the problem of hard and easy-to-collapse of the covering layer, and to develop new grouting material which is suitable for the construction of deep covering layer and excellent in physical and mechanical properties; and to optimize the existing curtain grouting. Construction equipment and process, and put forward a set of deep-cover curtain grouting construction technology, which is suitable for China's national conditions. A closed-cycle grouting method is adopted. (5) The seepage law and the operation condition of the anti-seepage body are mastered through the analysis of the seepage data of the dam foundation of the deep covering layer, and the seepage parameters of the dam foundation and the seepage-proof body are inverted by using the BP neural network based on the monitoring result of the seepage field, and the seepage field of the dam foundation is carried out The numerical simulation shows that the joint of different anti-seepage bodies should be strengthened under normal water storage condition, and the drainage area downstream of the anti-seepage body should be set up to avoid the damage; the elevation of the upstream dam slope and the inner infiltration line of the concrete under the condition of the water level of the reservoir is large, The influence of the downstream dam slope is small, and the inner seepage slope of the concrete cut-off wall and the anti-seepage curtain is reduced
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV543.5

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