前坪水库坝壳砂砾料工程特性试验研究

Experimental Study on the Engineering Characteristics of the Sand and Gravel Aggregate in the Dam Shell of Qianping Reservoir

以前坪水库西沟—鸭兰沟砂砾石料场为例,在试验代表性级配和控制干密度的条件下,通过大型压缩试验、三轴压缩试验、渗透试验分析了坝壳砂砾石料的变形、强度、渗透特性。试验结果表明:砂砾石料具有低压缩性,饱和固结排水剪与非饱和不固结不排水剪的应力-应变关系均呈应变硬化型,曲线形状比较接近双曲线,无明显剪胀现象;三轴压缩试验过程中的颗粒破碎较为明显,颗粒级配越粗,颗粒破碎率越大,颗粒破碎越明显;坝壳砂砾料的级配宽度不大,各级配砂砾料渗透破坏形式为管涌破坏,渗透系数差异不大,均表现出强透水特性。依托试验研究成果提出了适用于大坝应力-应变分析计算的邓肯-张模型参数和物理力学指标,为坝体设计和稳定性分析提供重要的参考依据,为火成岩地区地质环境条件类似的工程提供借鉴。

Taking the sand and gravel aggregate field of Xigou-Yalangou in Qianping Reservoir for an example,in the case of the representative gradations and control of dry density,the deformation,strength and permeability of the sand and gravel aggregate in the dam shell were analyzed by large compression test,triaxial compression test and penetration test. The experimental results showed that the sand and gravel aggregate had a low compressibility,its stress-strain relationship presented strain hardening under the conditions of the saturated consolidated drained shear and the non-saturated non-consolidated shear,the curve shape was close to a hyperbola,and no obvious shear dilation appeared. In triaxial compression test,the particle breakage was more obvious,the particle breakage rates were bigger when the particle graduations were lower,and the particle breakage was more obvious. The graduation width of the sand and gravel aggregate in the dam shell was not big,the permeation damage modes of the sand and gravel aggregate at every graduation level was piping failure,the difference of permeability coefficient was not obvious,and the sand and gravel aggregate presented strong permeable characteristics. Based on the experimental results,Duncan-Chang model and the physical and mechanical parameter indexes were proposed to analyze and calculate the stress-stain relationship of the dam,and the results would provide important references for the design and stability analysis of dam body,and could also provide some references for similar engineering in the local geological environment of igneous rock.