考虑循环围压与振动频率影响的饱和软黏土动力特性试验研究
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摘要
利用GDS变围压动三轴试验系统对宁波重塑饱和软黏土进行了一系列变围压不排水循环加载试验,重点研究了循环轴向偏应力和循环围压耦合作用下饱和软黏土不排水动力特性,分析了循环围压、振动频率对轴向累积应变及孔压的影响。研究结果表明:不排水条件下,循环轴向偏应力和循环围压耦合作用对试样的累积塑性应变发展具有一定的限制作用,轴向累积应变随应力路径斜率η及振动频率f的增大而减小。不同应力路径斜率、振动频率影响下,应变率随加载时间的变化规律一致,应力路径斜率η对应变率-时间关系影响较为明显,随着应力路径斜率η的增大,应变率减小,而不同振动频率条件下的应变率-时间关系曲线几近重合。最大孔压随循环围压的增加而增大,而随振动频率的增加而减小。在上述试验结果基础上,建立了呈线性关系的应变率与加载时间关系表达式。
A series of undrained cyclic triaxial tests under coupling effects of cyclic deviator stress and cyclic confining pressure is conducted on Ningbo remoulded saturated soft clay by using GDS cyclic triaxial system. The coupling effects of cyclic deviatoric stress and cyclic confining pressure on undrained dynamic behaviors are studied. The influences of cyclic confining pressure and vibration frequency on permanent axial strain and pore pressure are further analysed. The experimental results show that under undrained condition, coupling of cyclic deviator stress and cyclic confining pressure limits the development of the cumulative plastic strain of saturated soft clay to some extent. With the increasing of the slope of loading paths η and vibration frequency f, the permanent axial strain decreases. The relationships between permanent axial strain rate and cyclic time are identical under different stress paths and frequencies. The relationship between strain rate and cyclic time are more obviously affected by the slope of loading paths η comparing with the loading frequency, and the strain rate decreases with the increase of η. However, the curves of strain rate under different vibration frequencies almost coincide with each other. On the other hand, the maximum pore water pressure increases with the increase of cyclic confining pressure and decreases with the increase of vibration frequency. Based on the test results, a linear relationship between the permanent strain rate and cyclic time is established in log-log scale coordinates system.
A series of undrained cyclic triaxial tests under coupling effects of cyclic deviator stress and cyclic confining pressure is conducted on Ningbo remoulded saturated soft clay by using GDS cyclic triaxial system. The coupling effects of cyclic deviatoric stress and cyclic confining pressure on undrained dynamic behaviors are studied. The influences of cyclic confining pressure and vibration frequency on permanent axial strain and pore pressure are further analysed. The experimental results show that under undrained condition, coupling of cyclic deviator stress and cyclic confining pressure limits the development of the cumulative plastic strain of saturated soft clay to some extent. With the increasing of the slope of loading paths η and vibration frequency f, the permanent axial strain decreases. The relationships between permanent axial strain rate and cyclic time are identical under different stress paths and frequencies. The relationship between strain rate and cyclic time are more obviously affected by the slope of loading paths η comparing with the loading frequency, and the strain rate decreases with the increase of η. However, the curves of strain rate under different vibration frequencies almost coincide with each other. On the other hand, the maximum pore water pressure increases with the increase of cyclic confining pressure and decreases with the increase of vibration frequency. Based on the test results, a linear relationship between the permanent strain rate and cyclic time is established in log-log scale coordinates system.
引文
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[16]张曦,唐益群,周念清,等.地铁振动荷载作用下隧道周围饱和软黏土动力响应研究[J].土木工程学报,2007,40(2):85-88.ZHANG Xi,TANG Yi-qun,ZHOU Nian-qing,et al.Dynamic response of saturated soft clay around a subway tunnel under vibration load[J].China Civil Engineering Journal,2007,40(2):85-88.
[17]黄博,丁浩,陈云敏.高速列车荷载作用的动三轴试验模拟[J].岩土工程学报,2011,33(2):195-202.HUANG Bo,DING Hao,CHEN Yun-min.Simulation of high-speed train load by dynamic triaxial tests[J].Chinese Journal of Geotechnical Engineering,2011,33(2):195-202.
[18]GUO L,WANG J,CAI Y Q,et al.Undrained deformation behavior of saturated soft clay under long-term cyclic loading[J].Soil Dynamics and Earthquake Engineering,2013,50(7):28-37.
[19]张勇,孔令伟,郭爱国,等.循环荷载下饱和软黏土的累积塑性应变试验研究[J].岩土力学,2009,30(6):1542-1548.ZHANG Yong,KONG Ling-wei,GUO Ai-guo,et al.Cumulative plastic strain of saturated soft clay under cyclic loading[J].Rock and Soil Mechanics,2009,30(6):1542-1548.
[2]MIURA N,FUJIKAW K,SAKAI A.Field measurement of settlement in Saga airport highway subjected to traffic load[J].Soil Mechanics and Foundation Engineering,1995,43(6):49-51.
[3]周健,屠洪权.动力荷载作用下软黏土的残余变形计算模式[J].岩土力学,1996,17(1):54-60.ZHOU Jian,TU Hong-quan.A model for predicting the cyclic behavior of soft soil[J].Rock and Soil Mechanics,1996,17(1):54-60.
[4]MONISMITH C L,OGAWA N,FREEME C R.Permanent deformation characteristics of subgrade soils due to repeated loading[J].Transport Research Record,1975,537:1-17.
[5]LI D,SELIG T E.Cumulative plastic deformation for fine-grained subgrade soils[J].Journal of Geotechnical Engineering,1996,122(12):1006-1013.
[6]CHAI J C,MIURA N.Traffic-load-induced permanent deformation of road on soft subsoil[J].Journal of Geotechnical and Geoenvironmental Engineering,2002,128(11):907-916.
[7]陈颖平,黄博,陈云敏.循环荷载作用下软黏土不排水累积变形特性[J].岩土工程学报,2008,30(5):764-768.CHEN Ying-ping,HUANG Bo,CHEN Yun-min.Cumulative deformation behaviour of soft clay under undrained cyclic loading[J].Chinese Journal of Geotechnical Engineering,2008,30(5):764-768.
[8]臧濛,孔令伟,曹勇.描述循环荷载作用下黏土累积变形的改进模型[J].岩土力学,2017,38(2):435-442.ZANG Meng,KONG Ling-wei,CAO Yong.An improved model for cumulative deformations of clay subjected to cyclic loading[J].Rock and Soil Mechanics,2017,38(2):435-442.
[9]HYODO M,YASUHAHRA K,HIRAO K.Prediction of clay behaviour in undrained and partially drained cyclic triaxial tests[J].Soils and Foundations,1992,32(4):117
[10]SAKAI A,SAMANG L,MIURA A.Partially-drained cyclic behavior and its application to the settlement of a low embankment road on silty-clay[J].Soils and Foundations,2003,43(1):33-46.
[11]LEKARP F,ISACSSON U,DAWSON A.State of the art.I:resilient response of unbound aggregates[J].Journal of Transportation Engineering,2000,126(1):66-75.
[12]南京水利科学研究院.SL237-1999土工试验规程[S].北京:中国水利水电出版社,1999.Nanjing Hydraulic Research Institute.SL237-1999Specification of soil test[S].Beijing:4China Waterpower Press,1999.
[13]CAI Y Q,GU C,WANG J,et al.One-way cyclic triaxial behavior of saturated clay:comparison between constant and variable confining pressure[J].Journal of Geotechnical and Geoenvironmental Engineering,2013,139(5):797-809.
[14]谷川.基于变围压应力路径的饱和软黏土动力特性试验研究[D].杭州:浙江大学,2012.GU Chuan.Study on the dynamic behavior of saturated clays based on the stress paths with variable confining pressure[D].Hangzhou:Zhejiang University,2012.
[15]谷川,王军,蔡袁强,等.考虑变围压因素的饱和软黏土循环纯压动力特性试验研究[J].岩土工程学报,2013,35(7):1307-1315.GU Chuan,WANG Jun,CAI Yuan-qiang,et al.Undrained dynamic behaviors of saturated clays under compressive stress paths considering cyclic confining pressure[J].Chinese Journal of Geotechnical Engineering,2013,35(7):1307-1315.
[16]张曦,唐益群,周念清,等.地铁振动荷载作用下隧道周围饱和软黏土动力响应研究[J].土木工程学报,2007,40(2):85-88.ZHANG Xi,TANG Yi-qun,ZHOU Nian-qing,et al.Dynamic response of saturated soft clay around a subway tunnel under vibration load[J].China Civil Engineering Journal,2007,40(2):85-88.
[17]黄博,丁浩,陈云敏.高速列车荷载作用的动三轴试验模拟[J].岩土工程学报,2011,33(2):195-202.HUANG Bo,DING Hao,CHEN Yun-min.Simulation of high-speed train load by dynamic triaxial tests[J].Chinese Journal of Geotechnical Engineering,2011,33(2):195-202.
[18]GUO L,WANG J,CAI Y Q,et al.Undrained deformation behavior of saturated soft clay under long-term cyclic loading[J].Soil Dynamics and Earthquake Engineering,2013,50(7):28-37.
[19]张勇,孔令伟,郭爱国,等.循环荷载下饱和软黏土的累积塑性应变试验研究[J].岩土力学,2009,30(6):1542-1548.ZHANG Yong,KONG Ling-wei,GUO Ai-guo,et al.Cumulative plastic strain of saturated soft clay under cyclic loading[J].Rock and Soil Mechanics,2009,30(6):1542-1548.