脱水泥饼与加气混凝土粉混合料的抗剪强度特性研究

Shear strength characteristics of dewatered slurry cake-aerated concrete powder mixtures

为提高高含水率泥饼的抗剪强度,选用经破碎分选后的加气混凝土粉作为掺合料,利用大尺寸直剪仪开展泥饼与加气混凝土粉混合料的快剪试验,获得纯泥饼和混合料试样的剪应力-位移曲线,分析试样不排水抗剪强度在不同加气混凝土粉掺量、含水率和压实度下的变化规律,并利用筛分析法测试混合料在剪切前后的颗粒级配变化情况。研究结果表明:高含水率泥饼的不排水抗剪强度主要由黏聚力提供,其强度包络线近似为水平直线。混合料颗粒级配曲线在剪切后有所上移,说明剪切过程中发生了颗粒破碎现象,并且含水率越小、竖向压力越大,颗粒破碎程度越高。混合料不排水抗剪强度随着含水率减小、压实度增加而增加,但在压实度超过90%后,增加趋势明显减缓。加气混凝土粉主要是通过降低试样含水率来提高其不排水抗剪强度。对于深圳市含水率约42%的脱水泥饼,建议粉料掺量为30%,在此条件下,试样内摩擦角约为28°(压实度为80%),且试样含水率处于最优含水率附近。

In order to improve the shear strength of the dewatered slurry cake with high water content, the autoclaved aerated concrete powder was selected as the admixture, and the quick direct shear tests of the samples were carried out based on the large size direct shear apparatus. The shear stress-displacement curves of the samples were obtained, and the influence of autoclaved aerated concrete powder content, water content and compaction degree on the undrained shear strength of the samples were also analyzed based on the test results. The change of grain-size distribution of the samples were tested by sieve analysis before and after shearing. The results show that the undrained shear strength of the dewatered slurry cake with high water content is mainly provided by the cohesion, and its strength envelope is approximately a horizontal line. The grain-size distribution curves of the samples move upward after the quick direct shear tests, indicating that the particle is broken during the shearing process, and the degree of particle breaking increases with the decrease of water content and the increase of vertical load. The undrained shear strength increases with the decrease of water content and the increase of compaction degree. However, the increasing rate of undrained shear strength slows down obviously when the compaction degree exceeds 90%. The autoclaved aerated concrete powder improves the undrained shear strength of the samples mainly by reducing their water content. For the dewatered slurry cake with water content of about 42% in Shenzhen, the recommended autoclaved aerated concrete powder content is 30%. At this point, the internal friction angle of the sample is 28°(the compaction degree equals 80%), and the water content is near its optimum water content.