The soft rock was simulated by cement, plaster, sand, water, and concrete hardening accelerator in this paper. Meanwhile, uniaxial compressive strength tests and triaxial compression tests were conducted to study the mechanical properties of simulated soft rock samples. Model tests on a single pile socketed in simulated soft rock under axial cyclic loading were conducted by using a device which combined test apparatus with a GCTS dynamic triaxial system. Test results show that the optimal mix ratio is cement : plaster : medium sand : water : concrete hardening accelerator = 4.5% : 5.0% : 84.71% : 4.75% : 1.04%. The static load ratio (SLR), cyclic load ratio (CLR), and the number of cycles affect the accumulated deformation and cyclic secant modulus of the pile head. The accumulated deformation increases with increasing numbers of cycles. However, the cyclic secant modulus of pile head increases and then decreases with the growth in the number of cycles and finally remains stable after 50 cycles. According to the test results, the development of accumulated settlement was analysed. Finally, an empirical formula for accumulated settlement, considering the effects of the number of cycles, the static load ratio, the cyclic load ratio, and the uniaxial compressive strength, is proposed which can be used for feasibility studies or preliminary design of pile foundations on soft rock subjected to traffic loading.
In order to study strength and evaluate its quality of cement-soil in on-site construction process, unconfined compressive tests and triaxial CU shear tests were carried out on cement-soil core samples. The analysis of effects of cement mixing content, water cement ratio and lifting speed on strength and deformation properties of cement-soil was made. The results show that with the improvement of cement mixing ratio, the strength of cement-soil core samples is enhanced obviously, deformation modulus increases significantly, but the failure strain decreases, brittleness increases. And in the same conditions of cement mixing ratio, the strength of cement soil is higher when water cement ratio is 1.0 than that when water cement ratio is 0.8. And as the lifting speed increases, the density and strength of cement soil core samples are significantly reduced. This paper introduces the concepts of standard value, variable coefficient and modulus ratio, which can evaluate the density of cement soil core samples, unconfined compressive strength and the triaxial CU shear strength. This paper gives rational advice and is certain guide significance for practical projects.
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