压实膨润土膨胀力时效性试验及模型研究
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摘要
以压实膨润土为研究对象,对静置不同时间后试样的竖向膨胀力进行了试验研究和理论分析。首先将4种不同初始含水率的膨润土粉末压实到两种目标干密度,然后维持试样含水率不变,分别静置0,1,7,15,30 d和90 d,采用饱和膨胀仪对静置不同时间的试样进行膨胀力试验。试验结果表明:随着静置时间的增长,试样最大竖向膨胀力不断减小,且0～7 d减小明显,30 d之后趋于稳定。在此基础上,建立了考虑静置时间影响的压实膨润土膨胀力时效性经验模型,其中,膨胀力与静置时间的对数呈线性关系。模型参数讨论结果表明,初始膨胀力σ_0随初始吸力s的增加而线性增大;膨胀力衰减系数C_(Rσ)随吸力s的增加而线性减小。拟合结果表明该模型能够较好地反映压实膨润土的膨胀力时效性。
Taking compacted bentonite as the research object, the vertical swelling pressure of samples at different resting time was investigated by both experiment and theory. Firstly, bentonite powders with four different water contents were compacted to samples of two dry densities. Then, the compacted samples were rested for different periods(0, 1, 7, 15, 30 and 90 days). Afterwards, the samples were subjected to swelling pressure tests by using the swelling apparatus. Test results show that the maximum vertical swelling pressure of compacted bentonite decreases with the resting time. The swelling pressure decreases fast at the resting time of 0-7 days and then turns to be stable after 30 days resting. Based on test results, an empirical model considering aging effects of the swelling pressure of compacted bentonite is established. In the model, the swelling pressure decreases linearly with the logarithm of resting time. Discussion on the model parameters indicates that the initial swelling pressure increases linearly with initial suction whereas the decay index of swelling pressure decreases linearly with the increase of suction. Fitting results show that the established model can reflect well ageing effects of the swelling pressure of bentonite.
Taking compacted bentonite as the research object, the vertical swelling pressure of samples at different resting time was investigated by both experiment and theory. Firstly, bentonite powders with four different water contents were compacted to samples of two dry densities. Then, the compacted samples were rested for different periods(0, 1, 7, 15, 30 and 90 days). Afterwards, the samples were subjected to swelling pressure tests by using the swelling apparatus. Test results show that the maximum vertical swelling pressure of compacted bentonite decreases with the resting time. The swelling pressure decreases fast at the resting time of 0-7 days and then turns to be stable after 30 days resting. Based on test results, an empirical model considering aging effects of the swelling pressure of compacted bentonite is established. In the model, the swelling pressure decreases linearly with the logarithm of resting time. Discussion on the model parameters indicates that the initial swelling pressure increases linearly with initial suction whereas the decay index of swelling pressure decreases linearly with the increase of suction. Fitting results show that the established model can reflect well ageing effects of the swelling pressure of bentonite.
引文
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[14] 叶为民,唐益群,崔玉军.室内吸力量测与上海软土土水特征[J].岩土工程学报,2005,127(3):347-349.
[15] Lacerda W A.Houston W N.Stress relaxation in soils[C]//Proc.,8th ICSMFE,1973,1/34:221-227.
[2] Atomic Energy of Canada.Environmental Impact Statement on the Concept for Disposal of Canada's Nuclear Fuel Waste[R].AECL-10711,COG-93-1,1994.
[3] Japan Nuclear Cycle Development Institute.H12:Project to establish the scientific and technical basis for HLW disposal in Japan[R].Supporting Report 2,Repository Design and Engineering Technology,1999.
[4] Komine Hogata N.Experimental study on swelling characteristics of compacted bentonite[J].Canadian Geotechnical Journal,1994,31(4):478-490.
[5] Tripathy S,Sridharan A,Schanz T.Swelling pressures of compacted bentonites from diffuse double layer theory[J].Canadian Geotechnical Journal,2004(41):437-450.
[6] Villar M V,Lloret A Influence of dry density and water content on the swelling of a compacted bentonite[J].Applied Clay Science,2008,39(1/2):38-49.
[7] Komine H,Yasuhara K,Murakami S.Swelling characteristics of bentonites in artificial seawater[J].Canadian Geotechnical Journal,2009,46(2):177-189.
[8] Ye W M,Wan M,Chen B,et al.Temperature effects on the swelling pressure and saturated hydraulic conductivity of the compacted GMZ01 bentonite[J].Environmental Earth Sciences,2013(68):281-288.
[9] 孙德安,张龙.盐溶液饱和高庙子膨润土膨胀特性及预测[J].岩土力学,2013(10):2790-2795.
[10] Delage P,Marcial D,C Y J,et al.Ageing effects in a compacted bentonite:a microstructure approach[J].Géotechnique,2006,56:291-304.
[11] Day R W.Swell-shrink behaviour of expansive compacted clay[J].Journal of Geotechnical Engineering,1994,120(3):618-623.
[12] Subba Rao K S,Tripathy S.Effect of aging on swelling and swell-shrink behaviour of a compacted expansive soil[J].ASTM Geotechnical Test Journal,2003(26):36-46.
[13] 何彬,肖宏彬,尹铎霖,等.基于Sigmoid函数的膨胀土膨胀时程试验研究[J].人民长江,2017,48(21):108-114.
[14] 叶为民,唐益群,崔玉军.室内吸力量测与上海软土土水特征[J].岩土工程学报,2005,127(3):347-349.
[15] Lacerda W A.Houston W N.Stress relaxation in soils[C]//Proc.,8th ICSMFE,1973,1/34:221-227.