初始静孔隙水压力对砂土静动力剪切特性影响的试验研究
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摘要
选取福建标准砂和滹沱河细砂,利用空心圆柱扭剪仪开展了一系列不同初始静孔隙水压力条件下的不排水循环扭剪试验和单调扭剪试验,着重探讨初始静孔隙水压力对超静孔隙水压力发展及其不排水抗剪强度的影响。试验结果表明:初始静孔隙水压力对超静孔隙水压力的发展产生显著的影响,从而影响砂土的静动力剪切特性。具体地,在不排水循环剪切过程中,初始静孔隙水压力越大,其超静孔隙水压力发展和变形发展越快;在不排水单调剪切过程中,初始静孔隙水压力越大,在砂土剪胀阶段产生负超静孔隙水压力越大,从而使砂土的强度显著提高。基于试验结果,初步探讨了初始静孔隙水压力对超静孔隙水压力及静动力剪切特性的影响机理。研究表明,研究地下水位以下土体(准饱和土)静动力剪切特性尤其是研究液化问题时,应充分考虑初始静孔隙水压力对砂土抗液化强度的影响,室内试验应根据砂土所处的地下水位深度来决定初始静孔隙水压力(反压)的大小。
A series of undrained cyclic torsional shear tests and monotonic torsional shear tests are carried out on Fujian standard sand and Hutuo River fine sand under different initial static pore water pressures by using the hollow cylinder torsional shear apparatus in order to emphatically discuss the effects of the initial static pore water pressure on the development of the excess pore water pressure and undrained shear strength. The experimental results show that the initial static pore water pressure has a significant effect on the development of the excess pore water pressure, which affects the static and dynamic shear characteristics of sand. Specifically, during the undrained cyclic shear process, the greater initial static pore water pressure leads to the faster development of the excess pore water pressure and deformation. During the undrained monotonic shearing process, the greater the initial static pore water pressure, the greater the negative excess pore water pressure during the sand dilatancy, which significantly increases the strength of the sand. Based on the test results, the mechanism of the influences of the initial static pore water pressure on the excess pore water pressure and static and dynamic shear characteristics is preliminarily discussed. According to the results, the influences of the initial static pore water pressure on the anti-liquefaction strength of sand should be fully considered when we investigate the static and dynamic shear characteristics of soil(partially saturated soil) below the groundwater table, especially the liquefaction problem. In laboratory tests, the initial static pore water pressure(back pressure) should be determined according to the depth of underground water level where the sand is located.
A series of undrained cyclic torsional shear tests and monotonic torsional shear tests are carried out on Fujian standard sand and Hutuo River fine sand under different initial static pore water pressures by using the hollow cylinder torsional shear apparatus in order to emphatically discuss the effects of the initial static pore water pressure on the development of the excess pore water pressure and undrained shear strength. The experimental results show that the initial static pore water pressure has a significant effect on the development of the excess pore water pressure, which affects the static and dynamic shear characteristics of sand. Specifically, during the undrained cyclic shear process, the greater initial static pore water pressure leads to the faster development of the excess pore water pressure and deformation. During the undrained monotonic shearing process, the greater the initial static pore water pressure, the greater the negative excess pore water pressure during the sand dilatancy, which significantly increases the strength of the sand. Based on the test results, the mechanism of the influences of the initial static pore water pressure on the excess pore water pressure and static and dynamic shear characteristics is preliminarily discussed. According to the results, the influences of the initial static pore water pressure on the anti-liquefaction strength of sand should be fully considered when we investigate the static and dynamic shear characteristics of soil(partially saturated soil) below the groundwater table, especially the liquefaction problem. In laboratory tests, the initial static pore water pressure(back pressure) should be determined according to the depth of underground water level where the sand is located.
引文
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[15]SMEULDERS D M J.On wave propagation in saturated and partially saturated porous media[J].Thesis Technische Univ,1992.
[16]周新民.准饱和土波动特性及动力响应研究[D].杭州:浙江大学,2006.(ZHOU Xin-min.Research on wave Propagation characteristics and dynamic response in partially saturated soil[D].Hangzhou:Zhejiang University,2006.(in Chinese))
[2]AHNBERG H.Effects of back pressure and strain rate used in triaxial testing of stabilize dorganic soils and clays[J].Geotechnical Testing Journal,2004,27(3):250-259.
[3]ALLAM M M,SRIDHARAN A.Influence of the back pressure technique on the shear strength of soils[J].Geotechnical Testing Journal,1980,3(1):35-40.
[4]黄博,汪清静,凌道盛,等.饱和砂土三轴试验中反压设置与抗剪强度的研究[J].岩土工程学报,2012,34(7):1313-1319.(HUANG Bo,WANG Qing-jing,LING Dao-sheng,et al.Effects of back pressure on shear strength of saturated sand in triaxial tests[J].Chinese Journal of Geotechnical Engineering,2012,34(7):1313-1319.(in Chinese))
[5]HYODO M,YONEDA J,YOSHIMOTO N,et al.Mechanical and dissociation properties of methane hydrate-bearing sand in deep seabed[J].Soils and Foundations,2013,53(2):299-314.
[6]MIYAZAKI K,MASUI A,HANEDA H,et al.Variable-compliance-type constitutive model for methane hydrate bearing sediment[C]//Proceedings of the 6th International Conference on Gas Hydrate.Vancouver,2008.
[7]蒋明镜,朱方园,申志福.试验反压对深海能源土宏观力学特性影响的离散元分析[J].岩土工程学报,2013,35(2):219-226.(JIANG Ming-jing,ZHU Fang-yuan,SHENZhi-fu.Influence of back pressure on macro-mechanical properties of methane hydrate soils by DEM analyses[J].Chinese Journal of Geotechnical Engineering,2013,35(2):219-226.(in Chinese))
[8]许成顺,刘晨,刘海强,等.竖向-扭转双向耦合剪切仪功能析及应用[J].北京工业大学学报,2013(2):233-238.(XU Cheng-shun,LIU Chen,LIU Hai-qiang,et al.Function analysis and application of vertical-torsional coupling shear apparatus[J].Journal of Beijing University of Technology,2013(2):233-238.(in Chinese))
[9]李伟华,郑洁.饱和度对平面P波入射下自由场地地震反应的影响分析[J].岩土工程学报,2017,39(3):427-435.(LI Wei-hua,ZHENG Jie.Effects of saturation on free-field responses of site due to plane P-wave incidence[J].Chinese Journal of Geotechnical Engineering,2017,39(3):427-435.(in Chinese))
[10]许成顺,耿琳,杜修力,等.反压对土体强度特性的影响试验研究及其影响机理分析[J].土木工程学报,2016,49(3):105-111.(XU Cheng-shun,GENG Lin,DU Xiu-li,et al.Effect of back pressure on shear strength of sand:experimental studyand mechanism analysis[J].China Civil Egineering Journal,2016,49(3):105-111.(in Chinese))
[11]王明洋,钱七虎.爆炸波作用下准饱和土的动力模型研究[J].岩土工程学报,1995,17(6):103-110.(WANGming-yang,QIAN Qi-hu.Study on the dynamic model of partially saturated soil under the action of explosive wave[J].Chinese Journal of Geotechnical Engineering,1995,17(6):103-110.(in Chinese))
[12]刘建新,宋华,赵跃堂,等.准饱和砂土中平面压缩波传播[J].防灾减灾工程学报,2004,24(1):86-92.(LIUJian-xin,SONG Hua,ZHAO Yue-tang,et al.Propagation of plane compress-wave in quasic-saturated sandy soil[J].Journal of Disaster Prevention and Mitigation,2004,24(1):86-92.(in Chinese))
[13]王滢,高广运.准饱和土中圆柱形衬砌的瞬态动力响应分析[J].岩土力学,2015,36(12):3400-3409.(WANGYing,GAO Guang-yun.Analysis of transient dynamic response of cylindrical lined cavity in nearly saturated soil[J].Rock and Soil Mechanics,2015,36(12):3400-3409.(in Chinese))
[14]陈炜昀,夏唐代,黄睿,等.P1波在非饱和土地基表面的反射特性[J].工程力学,2013,30(9):56-62.(CHENWei-yun,XIA Tang-dai,HUANG Rui,et al.Reflection characteristics of P1 waves at the free boundray of unsaturated soil[J].Engineering Mechanics,2013,30(9):56-62.(in Chinese))
[15]SMEULDERS D M J.On wave propagation in saturated and partially saturated porous media[J].Thesis Technische Univ,1992.
[16]周新民.准饱和土波动特性及动力响应研究[D].杭州:浙江大学,2006.(ZHOU Xin-min.Research on wave Propagation characteristics and dynamic response in partially saturated soil[D].Hangzhou:Zhejiang University,2006.(in Chinese))