A Study On Compaction Characteristics And Disintegration Behavior Of Granite Residual Soil

Granite residual soil is widely distributed on Guangdong Province; the works of theFoundation, Excavation and Slope have become increasingly prominent with thedevelopment of infrastructure. The research background of the present thesis isgranite residual soil problems as a foundation pit on Shenzhen area. By conductingthe basic physical properties test, triaxial test, compaction test and disintegration testand so on laboratory test, the material composition and physical properties, thecompaction characteristics of the stress-strain relationship, the disintegrationcharacteristics, and the collapse of the failure mechanism of Granite residual soil arestudied as a more comprehensive analysis.The main research contents and results areas follows：Laboratory test is conducted to study physical and mechanical properties of Shenzhengranite residual soil. Study of test result proves that the granite residual soil porosityis relatively large, a high degree of differentiation, the natural state in the wet-a littlewet state, belonging to the high liquid limit clay. The obvious step on particle sizedistribution curve, the particles are not continuous phenomenon, the high content offine sand, come to that the granite residual soil particle size is “more than two, themiddle less” distribution characteristics.Laboratory test is conducted to study compaction characteristics of Shenzhen Graniteresidual soil. By conducting a light standard compaction test and found that the largeparticle content in the samples, soil samples re-use, height of more soil, on eachsample height and other factors to some extent affect the compaction effect. Drawthe conclusion that the maximum dry density for this article granite residual soilis1.449g/cm3，the optimum water content is22.0%，and is compared to the low withprevious research results, and slightly lower than range of the maximum dry density of the clay, combined with the particle analysis test, we can identify that this class ofgranite residual soil is residual cohesive soils.Laboratory triaxial test is conducted to study stress-strain behavior under differentcompaction indicators of Shenzhen granite residual soil. The results show that:Comparing the undisturbed sample with the reconstructed one, failure mode isdistinctively different, the undisturbed sample was shear failure, while thereconstructed sample was damage to the drum; The shear strength of undisturbed soilis significantly higher than to reconstructed one, while the most dense reconstructedsample under the condition of optimum water, its cohesive force is slightly largerthan the remolded samples, and its internal friction angle is less than the remoldedsamples; The stress-strain curve of the most dense reconstructed sample under thecondition of optimum water go to a concave shape early in the loading and astrain hardening in the low confining pressure, with the confining pressure increasedContinuous, the stress-strain curve transformed to the strain softening trend.Laboratory test is conducted to study disintegration characteristics in different statesabout Shenzhen granite residual soil. The results showed that: the granite residual soilwater that is disintegrating, there are three stages in the disintegration processgenerally about undisturbed soil samples, That is slow disintegration of the initialphase, the rapid disintegration of the middle stage, slow trend speed of disintegrationof later stages; While there are two stages in the disintegration process generallyabout reconstructed sample, That is rapid disintegration of the initial phase, and theslow disintegration of the later stages. The initial moisture content can accelerate thecollapse of the soil to a certain extent, but there is a largest water content; compactionbigger, faster disintegration rate; saturation can effectively inhibit the collapse of thesoil, reduce soil disintegration rate. The disintegration mechanism of granite residual soil is discussed on the basis of theabove studies, and combine with the related theory, this paper considers that there arethree disintegration of the failure mechanism about the granite residual soil, that ishydration, Wedge crack effect of the soil surface and dilution or dissolution of thecement, the three simultaneous and mutually reinforcing relationship exists betweeneach other, jointly intensify the development of soil softening disintegration.