试样尺寸及制样粒径大小对粗粒土三轴试验抗剪强度的影响

三轴试验是确定土的抗剪强度的主要方法,试样尺寸是影响三轴试验结果的重要因素之一.粗粒土的三轴试验需要采用大尺寸的试样进行,相应需要采用大尺寸试验装置及更多的制样用土.与大尺寸三轴试验相比,采用小尺寸三轴压力室,所需的试样较小,制样用土较少,且小尺寸三轴试验过程更快,试验成本更低.但采用小尺寸试样对粗粒土进行三轴试验时,往往得到偏小的抗剪强度参数,导致实际工程设计过于保守而不经济.为了降低试验成本,可以采用小尺寸试样进行试验,通过对试验结果进行修正来获得大尺寸试样试验结果,进而使工程设计具有良好的经济性.针对以上问题,本文对比研究了不良级配砾质砂混合物在采用去粗法前后制样试验所得的抗剪强度,提出了采用不同尺寸试样进行试验时对试验结果进行修正的方法及计算公式.

Study on sample size and grain size influence on shear strength of coarse-grained soil in triaxial test

Triaxial test is one of the most complete tests for determining the shear strength parameters of soils. Dimension of the specimens is one of the important factors affecting triaxial test results. Tri- axial testing of coarse-grained soils needs large-sized specimens, which requires large-scale apparatus and large amount of soil. Using the apparatus includes a small triaxial cell causes the test process to be conducted faster, due to using small specimens and small amount of soil is needed, therefore the cost of testing is reduced in comparison to the large-cell triaxial. The shear strength of poorly-graded gravelly sand mixtures before and after applying scalped gradation was investigated. Due to the lower shear strength parameters obtained from small specimens for coarse soils in triaxial testing it can lead to un- economic design. In order to reduce testing costs and more economic design for coarse soils, small spec- imens can be used instead of large specimens; in addition, the test results can be corrected. The corre- lation of the results of the different size specimens＇ triaxial tests was evaluated in this paper.