Research On Key Test Technology Of Consolidation And Shear Separation Of Remolded High Pressure Clay

The traditional method of consolidation and shearing performed sequentially on the same triaxial apparatus is too inefficient,making it extremely difficult to systematically carry out high-pressure mechanical tests of clay.In this paper,the deep clay of a mining area in East China is used as the research material,and the large-scale high-pressure suspension K₀ consolidation system is used to prepare large-scale saturated clay samples with a maximum stress of 4MPa.Based on this,dozens of standard tests that have completed high-pressure consolidation are prepared at one time.In this way,the uniformity and disturbance degree of the same batch of standard samples were evaluated through bending element and microscopic tests.The small size consolidation instrument with bending element system and the GDS triaxial testing machine were used for stress recovery,and the triaxial test was performed.Shear test,compare the shear strength of the same batch of mechanical specimens under consolidation and shear separation conditions,explore the key test techniques for reshaping high-pressure clay,and provide methods for subsequent high-pressure clay tests and undisturbed soil properties.The main research content and The results are as follows:This study first uses a large-size suspension high-pressure consolidation instrument to perform K₀ consolidation and cyclic loading and unloading tests on the clay.A 250×80mm large-size cylindrical high-pressure clay sample is obtained,and the water content test is carried out.It is concluded that the loading and unloading process In the K₀ change curve in,it is found that there is a clear difference between K₀ under normal pressure and high pressure,and K₀ increases with the increase of pressure;when the sample is in an over-consolidated state,the test data is fitted with the empirical formula to find that,K₀ has a strong correlation with the internal friction angle of the clay;comparative analysis of the stability standard of the high-pressure clay unloading process,it is recommended that the sample strain is less than 1×10^-4/8h as the unloading stable state;the water content deviation is very small,and the large-size sample is considered The uniformity is good.Secondly,through the bending element system,the large-size clay specimens obtained by consolidation and the specimens of different shapes obtained by cutting are tested for shear wave speed.It is concluded that the suitable excitation waveform for the clay bending element test is a square wave,and 10vpp should be selected.Excite amplitude and adopt peak-to-peak method as the method to determine the shear wave propagation time;the shear modulus of large-size clay specimens is slightly reduced after cutting,which is caused by slight disturbance of the specimen;the shear modulus of high-pressure clay exists Obvious anisotropy,the anisotropy ratio increases with the degree of disturbance.Using a small-size high-pressure consolidation instrument,the cut cylindrical mechanical specimens were subjected to a stress recovery test,and it was concluded that in the process,the specimen shear modulus gradually increased;based on the evaluation criteria of the relative change in the void ratio,the cylindrical mechanical specimens The sample quality of the mechanical sample is good.Using the GDS triaxial instrument to perform stress recovery and triaxial shear tests on the cylindrical mechanical samples prepared in batches of large-size clay samples,it is concluded that the K₀ path is taken to restore the original stress state to obtain more accurate test results.And it is not easy to cause the failure of the shear test;the samples show the characteristics of strain softening and dilatancy during the triaxial shearing process,and the pore pressure gradually rises with the strain;the shear strength of the same batch of small-sized samples is about 1400k Pa,and the deformation The law is consistent,indicating that the uniformity of the same batch of samples is good.Finally,the qualitative and quantitative analysis of the microstructure of the clay samples of different sizes shows that the particles mostly exist in the form of particle clusters under high pressure conditions,the particles are arranged more compactly,forming elongated connections,the pore distribution is more uniform,and the particle horizontal orientation law is obvious;The discreteness of each microstructure parameter is small,and it is considered that the batch sample preparation scheme under the conditions of consolidation and shear separation is more feasible..