Research On The Improvement And Application Of GDS True Triaxial Sand Sampler

Sand is a kind of granular material widely distributed on the earth.During the process of natural sedimentation,sand particles are arranged in the different spatial directions by the influence of gravity,while in the macroscopic scope,they are sand piles with a natural repose angle.Different sedimentation directions will bring diverse sedimentation angles of sand,which results in the anisotropy and dispersion of sand.The existing GDS true triaxial sand sampler can not control the different sedimentation angles of sand well.The original GDS sampler used in the test still has some shortcomings,such as uneven layered thickness of sand sample and inconvenient operation of sample preparation.Based on the above questions,the existing GDS true triaxial sand sampler has been improved,and the mechanical structure will be sampled.The film-bearing barrel is made of transparent material,and an angle adjusting device is added.In the control aspect,the driver and the steering gear are instructed by the upper computer software,and the improved sample-making device achieves the five angles required by the test through feedback adjustment.The GDS true triaxial test instrument was used to test the permeability saturation of the samples with different deposition angles prepared by the improved new sand sample preparation device,and to verify the reliability of the new sand sample preparation device.On the basis of the above research,the mechanical properties of sand with different deposition angles under complex stress paths were further studied by true triaxial shear test.Based on the above research,the conclusions are as follows:(1)The novel sand sampler adopts transparent material(PMMA),angle auto-adjusting device and interlayer of water injection in structure.It can achieve uniform stratification of different sedimentary angle for sand in the specimen preparation process and prepare six kinds of stratified sand samples with different sedimentary angles of 0,15,30,45,60 and 75 degrees;(2)Taking the sample preparation device as the control object,the CPU embedded in the steering gear is the controller and the digital steering gear as the actuator,the control system of the sample preparation device is completed by writing the control program in C language.Compared with the traditional device,the novel device improves the precision and preparation efficiency of different deposition angles of sand samples;(3)The novel sand preparation device is applied to the sand osmotic saturation test.The results show that the samples with six sedimentation angles present six corresponding permeability angles,which verifies the reliability of the device and improves the accuracy of the sand osmotic saturation test;(4)The novel sand preparation device is applied to the true triaxial test,the results show that the shear strength and dilatancy of sand samples decrease with the increase of deposition angle.