The Large-Sale Direct Shear Experimental Investigation Of Coarse Dust Soil

The large-scale direct shear experiment on the Coarse dust soil is a very complex geotechnical experiment. The large-scale direct shear machine, Preparation of soil, Filler, Shear etc are discussed in this thesis. The research on the Coarse grained soil is rare, specially on the large-scale shear experiment. In the engineering practice, the correct selection on the shear strength of soil is very important, the selection of unsuitable standard always makes the computing results violate the correct value, which will affect the computational accuracy, or even generates the engineering catastrophe. The selection of shear strength needs to depends on the characteristics of soil, the geology condition, the detailed engineering condition (such as the class of building, the construction field, and the speed of construction) etc. and make the experimental technique match the real condition. The different bottom material and the capacity of coarse grained soil will be used as the control target of current experiments by the author, after the large-scale experiment of three axis the different varying rules of the parameter of shear-strength of coarse material vs different experimental condition, the final goal of this paper is to find a reliable experimental method and shear strength parameters.The shear experiments of two soil bottom material with some ratio rocks are performed in this paper, after which the following conclusions can be drawn:The calibration experiments on the horizontal lift jack and vertical one are done by the testing force circle. Since this facility is not standard one, the parameters of such facility can not be ascertained. And the precondition of making an accurate shear experiment is to do the calibration experiment of lifting jack. The results of calibration basically agree with the values presented on the control panel of facilities.By comparing and analyzing the results from the large-scale shear experiment of standard Shi Yingsha. the experiment of piling sand, the single-axis pressure test, the adjustment on the large-scale shear facility is finished. The adjustment results are that the real value equals the internal mo ca angle generated by the large-scale shear machine subtract2degree.The debris flow which size is less than10mm can be chosen as bottom material, through the shear test with the mixture (different proportion in stone), it is shown that:1the internal friction angle φ1of bottom material is less than the internal angle φ2the material which contain the big particle. And the value of φ1increased with the proportion of the big particle increasing.2. When the proportion of the big particle is less than20%, the value of φ2changed little, it is shown that the shear strength of the mixture is determined by the bottom material.3. When the proportion of the big particle increasing from20%to50%, the valve of φ2increasing. The bottom material filled in the voids of the big particles, there are some big particles direct contact. The shear strength of mixture is gradually increasing with the increasing of the large particle.4. When the proportion of the big particle is more than50%, the value of φ2changed little. Once the proportion reaches50%, a intact framework structure formed by the interlocking stable particles. The small particle filled in the voids of large particles, which improve the compactness of the mixture. The integral strength of mixture is depends on the large particle. So the critical condition of forming framework structure is defined as the proportion of the large particle is reach50%.