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Experimental Study on Consolidation and Creep of Expansive Soil

Author: ZuoZuo
Tutor: XiaoHongBin
School: Hunan University
Course: Geotechnical Engineering
Keywords: expansive soil creep consolidation coupling model
CLC: TU411
Type: Master's thesis
Year: 2010
Downloads: 86
Quote: 0
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Abstract


Expansive soil is widely distributed around the world, which frequently causes a great amount of engineering accidents and brings great economy loss to many countries. Structures built on expansive soils such as municipal engineering, speedways, express railways and retaining walls will be unstable and damaged gradually with time, moreover, long-term settlements of foundation, ground settlements and deformation of tunnel in construction have relationship with its consolidation and creep characteristics, which has been successfully reported by many engineering cases and research on those constructions within the zone of expansive soil. However, studies on consolidation and creep characteristics of expansive soil have not been reported up till now. So, it’s very essential and urgent to carry out systematical research on expansive soil. Based on present domestic and international studies on consolidation and creep characteristics in soils and comprehensive analysis, this dissertation, supported by the National Natural Science Fund, Hunan Province Natural Science Fund and Key Financial Aid Project of Hunan Education Department, contributes many efforts to study consolidation and creep characteristics of Nanning expansive soil. By means of combining the research with experiments in-doors, model tests, theoretical analysis and numerical analysis, the study has been accomplished with the following achievements:1) A series step-loading consolidation tests under different loading ratio and preloading or no preloading condition for statured expansive soil have been conducted. The results show as follows:Under no preloading condition, samplers with different loading ratio, have different e-t log curves. Curves present relatively flat when the loading ratio is small, while Curves present obvious bending when the loading ratio is large. To those samples with preloading, changing trends of the curves of e-t log curves are different between p< 200 kPa and p> 200 kPa. Preloading and no preloading consolidation Comparison test results prove that preloading is beneficial to reduce the effect of total strain and creep. However, the effect of preloading is impacted by expansive soil swelling. Empirical formula for the e-lgp andε-t curves has been presented.2) A series tests were done for unsaturated Nanning expansive soil and Zhuzhou red clay, including consolidation and creep coupling test, rebound test, a microstructure study by electron microscope. Compared with the red clay, expansive soil has more significant rheological properties. Under entirely confined, the creep of expansive soil is not any development. Based on Analysis and comparison of tests curves two soils, corresponding empirical formula has been presented, and calculated curves fit well with the measured curves. By electron microscopy of the microstructure, the micro macro experiment conclusions can be permitted.3) The shear strain-time curves of Nanning unsaturated expansive soils under different vertical pressure can be got by means of creep testing apparatus controlled by shearing force. The results show that: When the stress level is below the yield limit, Nanning unsaturated expansive soil perform for attenuation, but when the stress level is higher than the yield limit, Nanning unsaturated expansive soil have obvious non-linear rheological properties generally. Its empirical creep equation can be determined by shear strain-time curves. During the shear creep process, Consolidation and creep of expansive soils is coupled.4) According to the numerical analysis compression creep and shear creep, an improved model for compression creep of expansive soil and a red clay model for compression creep of red clay are proposed, respectively, and a comparison of the two models is made. In the shear creep tests, Nanning unsaturated expansive soil, in certain water contents, can use this improved model to fit.

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CLC: > Industrial Technology > Building Science > Soil mechanics,foundation engineering > Soil Test > Laboratory tests (indoor soil test )
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