试样尺寸对粗粒土强度及变形试验影响研究

Study on Effect of Specimen Size upon Strength and Deformation Behaviour of Coarse-grained Soil in Triaxial Test

对某堆石料进行了3种(大、中、小)不同直径试样的三轴固结排水剪切试验,研究在不同试样尺寸下粗粒土的应力-应变及强度特性差异,初步探讨了试样尺寸大小对应力-应变及强度性质的影响。结果表明:不同尺寸大小的试样所测定的应力-应变关系及剪胀性相似,但量值大小有差异;对相同围压下同一种级配粗粒土,较小尺寸试样峰值强度高于较大尺寸试样的强度,随着试样尺寸的增大,增加幅度呈减小趋势;低围压下试样直径变化引起的摩擦角测定值变化较大,高围压下直径影响变小。对应1%应变的割线杨氏模量和体积模量随试样大小有一定程度的变化,其变化规律有待更多试验验证。

The conventional consolidated drained triaxial compression tests with three specimen dimensions were performed, and differ- ence of the stress-strain behavior and shear strength between specimens at different sizes of a coarse-grained soil were investigated. The effect of specimen size on the behavior was studied. The test resuhs showed that the stress-strain relation and the dilatancy for speci- mens with different size exhibit similar behavior, and the value is different. For the soil with the same cell pressure and gradation, the peak deviatoric stress of smaller specimen is higher than that of larger specimen, and the difference of the peak deviatorie stress decrea- ses with the increase of specimen size. At lower cell pressure, variation of specimen size induces larger change of friction angle, and at higher pressure, the effect of specimen size on the angle becomes small. The Young＇ s modulus and bulk modulus also change with the specimen size, and the law is to be verified by more test results.