压实系数对粗粒土剪切特性的影响

压实系数是控制填方体工程质量的重要指标,但目前关于压实系数对填料剪切特性的影响研究还不够深入。采集重庆江北机场扩建工程回填夯实的粗粒土制备不同压实系数的重塑试样,通过室内大型直剪试验,研究了粗粒土在不同压实系数下的剪切特性,结果表明:高法向应力,低压实系数时,粗粒土表现为应变硬化和剪缩现象;低法向应力,高压实系数时,则表现为应变软化和剪胀现象;粗粒土在剪切过程中表现出“结构性”和“摩擦性”,“结构性”发挥在先,“摩擦性”在后;压实系数对剪切强度有增大效应,但法向应力对这种增大效应有削弱作用;压实系数对粘聚力有增大效应,但对内摩擦角的影响不显著;剪切破坏面上遇到粗颗粒时所表现出的“饶石”、“穿石”、“夹石”现象会随粗颗粒的强度、尺寸以及法向应力等因素的变化而互相转换。

Effect of Compaction Coefficient on Shear Characteristics of Coarse Grained Soil

Compaction coefficient is an important index of controlling construction quality of fill body,but study on compaction coefficient's influence on fill body shear characteristics is not deep enough.Backfill ramming coarse grained soil of Chongqing Jiangbei airport expansion project was collection to prepare remaking samples of different compacting coefficient.Lab large scale direct shear tests were conducted to study shear characteristics of coarse grained soil under different compaction coefficient.The results show:coarse grained soil is characterized by strain hardening and shear shrinkage phenomenon under high normal stress and low compaction coefficient,and strain softening and shear dilatancy phenomenon under low normal stress and high compaction coefficient;coarse grained soil shows " structure property" and "friction property" in shearing process,in which "structure property" plays first and "friction property" plays second;compaction coefficient has an effect to increase shear strength,but normal stress weakens the increase effect;compaction coefficient has an effect to increase cohesion force,but the influence to internal friction angle was not significant;on the shear failure plane,the phenomenon of coarse particles,"by passing stone","traversing stone","clamping stone",converts to each other with the changes of coarse particles,such as strength,size,or normal stress.