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Test Research of Properties on Rebounded Deformation and Pore Water Pressure of Soft Clay under Unloading Condition

Author: LeiJun
Tutor: TangBin
School: Wuhan University of Science and Technology
Course: Geotechnical Engineering
Keywords: soft soil unload rebound deformation pore water pressure test study
CLC: TU470
Type: Master's thesis
Year: 2010
Downloads: 89
Quote: 0
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Abstract


Soil will cause deformation under load ,and rebound deformation will occur when unloading. There is great discrepancy in the properties of soft soil when loading and unloading. Based on predecessor’s foundation, triaxial apparatus were improved due to requirements of the tests.The consolidation tests, rebounded deformation tests and pore water suction tests could be carried out.The relationships between rebounded deformation and time, between unload ratios and void ratio,between the maximum rebounded deformation were researched thought the improved triaxial apparatus.The result showed that the soft soil in Wuhan area existed two critical unload ratios that was 0.4 and 0.9.When the soft soil’s unload ratio 0<R<0.3 and R>0.9, rebounded deformation of the soft soil would not happen ,no matter what the pre-consolidation load was.When 0.3<R<0.9, the rebounded deformation would occurred whose value surged when unloading and just increased a little in the 24h.Secondly the properties between pore water pressure and time under loading and unloading,the relationship between the maximum pore water pressure and unloading weight.The research showed that the pore water pressure was quite differently as time changed under loading and unloading.In unloading condition,the value of pore water pressure was negative.It reached the negative maximum in short time an then increased until the value was 0 kPa.The maximum negative value was related to the unloading weight and it increased and increased as the unloading weight grew.Then the pore water content in the soft soil during the loading and unloading process,relationship between water suction and void ratio,relationship between water suction in loading process and discharge of water in consolidation condition.The result showed that there existed critical ratio that is 0.3 and 0.9.When 0<R<0.3 and R>0.9, the water that leaved the soft soil during consolidation would not be drawn back to the soil;When 0.3<R<0.9,rebounded deformation would happen and the water would be sucked.The water content which was drawn back to the soft soil was about 9 percent of the water quality that leaved the soil.In the end,this paper analyzed field data from a road project , which showed the tests and the engineering practise closely meet .With the analysis and study of properties of rebounded deformation for soft soil,the author promoted a improved surcharge preloading method for soft soil treatment.

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CLC: > Industrial Technology > Building Science > Soil mechanics,foundation engineering > Foundation > The foundation and basis for the theory and computational
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