高砾石含量心墙土的水力破坏试验研究

心墙水力破坏是高心墙堆石坝主要安全问题之一,采用中型应力路径三轴仪开展高砾石含量心墙土的水力破坏试验,研究了围压、砾石含量和注水速率等因素对其特性的影响,提出了砾石土内部组成的抽象模型和高砾石含量下水力击穿破坏的发生机理,并探讨了水力击穿演进过程及其与水力劈裂的联系。结果表明:试样在偏应力作用下固结后,通过试样中心预置的水流通道不断提高试样内部水压力,当内部水压力升至略高于围压时,试样出现水力破坏;以注入试样中的水量大幅度增加,但注水压力不增加时对应的内部水压力作为水力破坏压力,其与围压的比值随砾石含量的增大而减小,并随围压和注水速率的增大而增大;试验在高砾石含量范围内(砾石含量35%~50%),试样破坏时外表面有分散出水点,破坏路径在试样内部呈不规则线,水力破坏模式为水力击穿。

Experimental study on hydraulic fracturing of soil with high gravel content for core-wall

The hydraulic fracturing of earth core-wall is one of the major safety problems for high rockfill dam. A hydraulic fracturing experiment on the soil with high gravel content for the core-wall is made with medium sized stress path triaxial apparatus，from which the influences from the factors of confining pressure，gravel content，water-filling rate，etc. on its characteristics are studied herein，and then the abstract model of the inner composition of the gravel soil and the occurrence mechanism of the hydraulic fracturing of the soil with high gravel content are put forward，while the relation between the evolutionprocess of the hydraulic breakdown and the hydraulic fracturing is discussed as well. The result shows that after the consolidation of the sample under the effect of deviated stress，the internal water pressure of the sample is gradually increased through the water-flowing path preset in the center of it. When the internal water pressure rises to a little bit higher than the confining pressure，hydraulic fracturing occurs on the sample. Taking the corresponding internal water pressure when largely increasing the water amount filled into the sample without increasing the water-filling pressure as the hydraulic fracturing pressure，the ratio between the hydraulic fracturing pressure and the confining pressure decreases along with the increase of the gravel content，and futhermore，increases along with the increases of both the confining pressure and the water-filling rate. The experiment is carried out within the range of high gravel content (35% ～ 50% )，in which dispersed water exits occur on the outer surface of the sample when the sample is fractured with the fracturing path with irregular line inside of the sample，thus the hydraulic fracturing mode is the hydraulic breakdown.