考虑时间间歇效应的地铁列车荷载下海相软土长期动力特性试验研究
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摘要
软土地基在地铁运营期受到周期性振动和间歇的反复作用,间歇期内软土力学特性的变化将影响其长期动力响应,但以往关于交通荷载下软土动力特性的研究大多忽视时间间歇的影响。考虑不同动应力水平、不同振动和间歇时长的耦合作用,设计一系列不排水连续–停振循环三轴试验,采用K0固结条件,研究原状海相软土在列车非连续荷载下的长期孔压、变形特性,通过与连续振动试验对比,发现荷载间歇对软土动力特性有显著影响,由于间歇期动力特性改变,软土后续加载稳定时的最大残余孔压和应变明显降低,且孔压、应变响应趋于稳定时所需的振次减少而时间增加。基于试验结果,深入分析时间间歇效应的作用机制和间歇时长对软土长期动力特性的影响。结果表明:间歇期软土内结构进一步调整使得振动期激振停止时部分未及时恢复的弹性后效孔压和应变得以恢复,这部分孔压和应变在振动期重复发生,导致按传统方式计算出的振动期表观残余孔压和应变总和远大于连续振动;同等条件下,间歇时长越长,软土孔压和应变响应被削弱程度越大,达到稳定时的最大残余孔压和应变越小,进入稳定期所需时间越长。研究对于地铁荷载下软土地基长期沉降的计算分析有推动意义。
Soft soil foundations are repeatedly subjected to periodic vibration and time intermittence during the subway operation period. The mechanical characteristics of soft soils in intermittent periods will affect their long-term dynamic characteristics,but most of previous researches on the dynamic characteristics of soft soils under traffic loads neglected the effect of time intermittence. Considering different dynamic stress levels and coupling effects of different vibration times and intermittence times,a series of undrained continuous-stopping vibration triaxial tests were designed to study the long-term pore pressure and deformation characteristics of the undisturbed K0 consolidated marine soft clay under uncontinuous subway loads. By comparing with the continuous vibration tests, it was found that the intermittence has a significant effect on the dynamic characteristics of the soft soil. Due to the change of the dynamic characteristics during the intermittent period,the maximum residual pore pressure and strain of the soft soil after loading stabilization decrease obviously,and the number of vibrations required to stabilize the pore pressure and the strain decreases while the time increases. Based on the test results,the mechanism of time interval effect and the influence of intermittence time on dynamic characteristics of soft soil were analyzed in depth. It is shown that the further adjustment of the internal structure of the soft soil during the intermittent period reduces the elastic aftereffect pore pressure and the strain that fail to recover in time during the vibration period,and that the partial pore pressure and the strain repeatedly occur in the vibration period,which makes the calculated residual pore pressure and strain are far greater than those resulted from the continuous vibration. Under the same condition,the longer the intermittence time is,the greater the pore pressure and the strain response of the soft soil are weakened,the smaller the maximum residual pore pressure and the strain are,and the longer the time required to enter a stable period. This study has a positive significance for calculating the long-term settlement of soft soil foundations under subway loads.
Soft soil foundations are repeatedly subjected to periodic vibration and time intermittence during the subway operation period. The mechanical characteristics of soft soils in intermittent periods will affect their long-term dynamic characteristics,but most of previous researches on the dynamic characteristics of soft soils under traffic loads neglected the effect of time intermittence. Considering different dynamic stress levels and coupling effects of different vibration times and intermittence times,a series of undrained continuous-stopping vibration triaxial tests were designed to study the long-term pore pressure and deformation characteristics of the undisturbed K0 consolidated marine soft clay under uncontinuous subway loads. By comparing with the continuous vibration tests, it was found that the intermittence has a significant effect on the dynamic characteristics of the soft soil. Due to the change of the dynamic characteristics during the intermittent period,the maximum residual pore pressure and strain of the soft soil after loading stabilization decrease obviously,and the number of vibrations required to stabilize the pore pressure and the strain decreases while the time increases. Based on the test results,the mechanism of time interval effect and the influence of intermittence time on dynamic characteristics of soft soil were analyzed in depth. It is shown that the further adjustment of the internal structure of the soft soil during the intermittent period reduces the elastic aftereffect pore pressure and the strain that fail to recover in time during the vibration period,and that the partial pore pressure and the strain repeatedly occur in the vibration period,which makes the calculated residual pore pressure and strain are far greater than those resulted from the continuous vibration. Under the same condition,the longer the intermittence time is,the greater the pore pressure and the strain response of the soft soil are weakened,the smaller the maximum residual pore pressure and the strain are,and the longer the time required to enter a stable period. This study has a positive significance for calculating the long-term settlement of soft soil foundations under subway loads.
引文
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[12]蒋昱州,王瑞红,朱杰兵,等.砂岩的蠕变与弹性后效特性试验研究[J].岩石力学与工程学报,2015,34(10):2 010-2 017.(JIANGYuzhou,WANG Ruihong,ZHU Jiebing,et al.Experimental study of creep and elastic aftereffect of sandstone[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(10):2 010-2 017.(in Chinese))
[13]丁伯阳,张勇.杭州第四系软土动力特性试验与土结构性影响的探讨[J].岩土力学,2012,33(2):336-342.(DING Boyang,ZHANGYong.Discussion on dynamic test and characteristics of structural properties of Quaternary soft clay in Hangzhou region[J].Rock and Soil Mechanics,2012,33(2):336-342.(in Chinese))
[14]YILDIRIM H,ERSAN H.Settlements under consecutive series of cyclic loading[J].Soil Dynamics and Earthquake Engineering,2007,27:577-585.
[15]王军,蔡袁强,郭林,等.分阶段循环加载条件下温州饱和软黏土孔压和应变发展规律[J].岩土工程学报,2012,34(7):1 349-1 354.(WANG Jun,CAI Yuanqiang,GUO Lin,et al.Pore pressure and strain development of Wenzhou saturated soft soil under cyclic loading by stages[J].Chinese Journal of Geotechnical Engineering,2012,34(7):1 349-1 354.(in Chinese))
[16]丁建宇,王朝亮,杜运国,等.排水条件下阶段性循环荷载作用对饱和软黏土动力特性影响[J].世界地震工程,2017,33(2):161-168.(DING Jianyu,WANG Chaoliang,DU Yunguo,et al.Influence of staged cyclic loading on dynamic behavior of saturated soft clay under drained condition[J].World Earthquake Engineering,2017,33(2):161-168.(in Chinese))
[17]中华人民共和国行业标准编写组.SL 237-1999土木试验规程[S].北京:中国水利水电出版社,1999.(The Professional Standards Compilation Group of People′s Republic of China.SL 237-1999Specification of soil test[S].Beijing:China Water Power Press,1999.(in Chinese))
[18]张坤勇,李广山,梅小洪,等.基于K0固结排水卸荷应力路径试验粉土应力-变形特性研究[J].岩土工程学报,2017,39(7):1 182-1 188.(ZHANG Kunyong,LI Guangshan,MEI Xiaohong,et al.Stressdeformation characteristics of silty soil based on K0 consolidation and drainage unloading stress path tests[J].Chinese Journal of Geotechnical Engineering,2017,39(7):1 182-1 188.(in Chinese))
[19]王常晶,陈云敏.列车荷载在地基中引起的应力响应分析[J].岩石力学与工程学报,2005,24(7):1 178-1 186.(WANG Changjing,CHEN Yunmin.Analysis of stresses in train-induced ground[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(7):1 178-1 186.(in Chinese))
[20]顾中华.循环荷载作用下偏压固结饱和黏土孔压模型[J].地下空间与工程学报,2007,3(4):776-780.(GU Zonghua.The excess pore-water pressure model of anisotropic consolidated saturated clay under cyclic loading[J].Chinese Journal of Underground Space and Engineering,2007,3(4):776-780.(in Chinese))
[21]年延凯,焦厚滨,范宁,等.南海北部陆坡软勃土动力应变-孔压特性试验[J].岩土工程学报,2018,39(5):1 564-1 572.(NIANYankai,JIAO Houbin,FAN Ning,et al.Experiment on dynamic strain-pore pressure of soft clay in the northern slope of South China Sea[J].Chinese Journal of Geotechnical Engineering,2018,39(5):1 564-1 572.(in Chinese))
[2]WANG D,ZENTAR R,ABRIAK N E,et al.Long-term mechanical performance of marine sediments solidified with cement,lime and fly ash[J].Marine Georesources and Geotechnology,2017,36(1):123-130.
[3]陈基炜,詹龙喜.上海市地铁一号线隧道变形测量及规律分析[J].上海地质,2000,21(2):51-56.(CHEN Jiwei,ZHAN Changxi.Deformation measuring of the metro tunnel and deformation data analysis of Shanghai metro line No.1[J].Shanghai Geology,2000,21(2):51-56.(in Chinese))
[4]倪静,INDRARATNA B,耿雪玉,等.循环荷载水平与加载频率耦合作用下的软黏土特性研究[J].工程力学,2014,31(10):167-173.(NI Jing,INDRARATNA B,GENG Xueyu,et al.Experimental study of the combined effect of cyclic stress level and loading frequency on the performance of soft clays[J].Engineering Mechanics,2014,31(10):167-173.(in Chinese))
[5]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.
[6]OH T M,BANG E S,CHO G C,et al.Estimation of undrained shear strength for saturated clay using shear wave velocity[J].Marine Geotechnology,2017,35(2):236-244.
[7]丁智,范俊靓,张孟雅,等.地铁列车荷载下原状土孔压及应变模型试验研究[J].铁道学报,2017,39(3):96-103.(DING Zhi,FAN Junliang,ZHANG Mengya,et al.Experimental study on pore pressure and strain model of undisturbed soil under subway dynamic loading[J].Journal of the China Railway Society,2017,39(3):96-103.(in Chinese))
[8]唐益群,张曦,赵书凯,等.地铁振动荷载下隧道周围饱和软黏土的孔压发展模型[J].土木工程学报,2007,40(4):82-86.(TANGYiqun,ZHANG Xi,ZHAO Shukai,et al.Model of pore water pressure development in saturated soft clay around a subway tunnel under vibration load[J].China Civil Engineering Journal,2007,40(4):82-86.(in Chinese))
[9]丁智,魏新江,庄家煌,等.地铁列车荷载下冻融土刚度软化试验研究[J].岩石力学与工程学报,2018,37(4):987-995.(DINGZhi,WEI Xinjiang,ZHUANG Jiahuang,et al.Experimental study on stiffness softening of frozen-thawed soil under subway loading[J].Chinese Journal of Rock Mechanics and Engineering,2018,37(4):987-995.(in Chinese))
[10]丁智,张孟雅,魏新江,等.地铁循环荷载下冻融软土孔压发展及微观结构研究[J].岩石力学与工程学报,2016,35(11):2 328-2 336.(DING Zhi,ZHANG Mengya,WEI Xinjiang,et al.Study on pore pressure and microstructure of frozen and thawed soft soil under subway cyclic loading[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(11):2 328-2 336.(in Chinese))
[11]刘明,黄茂松,柳艳华.车振荷载引起的软土越江隧道长期沉降分析[J].岩土工程学报,2009,31(11):1 703-1 709.(LIU Ming,HUANG Maosong,LIU Yanhua.Long-term settlement of tunnels across a river induced by vehicle operation[J].Chinese Journal of Geotechnical Engineering,2009,31(11):1 703-1 709.(in Chinese))
[12]蒋昱州,王瑞红,朱杰兵,等.砂岩的蠕变与弹性后效特性试验研究[J].岩石力学与工程学报,2015,34(10):2 010-2 017.(JIANGYuzhou,WANG Ruihong,ZHU Jiebing,et al.Experimental study of creep and elastic aftereffect of sandstone[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(10):2 010-2 017.(in Chinese))
[13]丁伯阳,张勇.杭州第四系软土动力特性试验与土结构性影响的探讨[J].岩土力学,2012,33(2):336-342.(DING Boyang,ZHANGYong.Discussion on dynamic test and characteristics of structural properties of Quaternary soft clay in Hangzhou region[J].Rock and Soil Mechanics,2012,33(2):336-342.(in Chinese))
[14]YILDIRIM H,ERSAN H.Settlements under consecutive series of cyclic loading[J].Soil Dynamics and Earthquake Engineering,2007,27:577-585.
[15]王军,蔡袁强,郭林,等.分阶段循环加载条件下温州饱和软黏土孔压和应变发展规律[J].岩土工程学报,2012,34(7):1 349-1 354.(WANG Jun,CAI Yuanqiang,GUO Lin,et al.Pore pressure and strain development of Wenzhou saturated soft soil under cyclic loading by stages[J].Chinese Journal of Geotechnical Engineering,2012,34(7):1 349-1 354.(in Chinese))
[16]丁建宇,王朝亮,杜运国,等.排水条件下阶段性循环荷载作用对饱和软黏土动力特性影响[J].世界地震工程,2017,33(2):161-168.(DING Jianyu,WANG Chaoliang,DU Yunguo,et al.Influence of staged cyclic loading on dynamic behavior of saturated soft clay under drained condition[J].World Earthquake Engineering,2017,33(2):161-168.(in Chinese))
[17]中华人民共和国行业标准编写组.SL 237-1999土木试验规程[S].北京:中国水利水电出版社,1999.(The Professional Standards Compilation Group of People′s Republic of China.SL 237-1999Specification of soil test[S].Beijing:China Water Power Press,1999.(in Chinese))
[18]张坤勇,李广山,梅小洪,等.基于K0固结排水卸荷应力路径试验粉土应力-变形特性研究[J].岩土工程学报,2017,39(7):1 182-1 188.(ZHANG Kunyong,LI Guangshan,MEI Xiaohong,et al.Stressdeformation characteristics of silty soil based on K0 consolidation and drainage unloading stress path tests[J].Chinese Journal of Geotechnical Engineering,2017,39(7):1 182-1 188.(in Chinese))
[19]王常晶,陈云敏.列车荷载在地基中引起的应力响应分析[J].岩石力学与工程学报,2005,24(7):1 178-1 186.(WANG Changjing,CHEN Yunmin.Analysis of stresses in train-induced ground[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(7):1 178-1 186.(in Chinese))
[20]顾中华.循环荷载作用下偏压固结饱和黏土孔压模型[J].地下空间与工程学报,2007,3(4):776-780.(GU Zonghua.The excess pore-water pressure model of anisotropic consolidated saturated clay under cyclic loading[J].Chinese Journal of Underground Space and Engineering,2007,3(4):776-780.(in Chinese))
[21]年延凯,焦厚滨,范宁,等.南海北部陆坡软勃土动力应变-孔压特性试验[J].岩土工程学报,2018,39(5):1 564-1 572.(NIANYankai,JIAO Houbin,FAN Ning,et al.Experiment on dynamic strain-pore pressure of soft clay in the northern slope of South China Sea[J].Chinese Journal of Geotechnical Engineering,2018,39(5):1 564-1 572.(in Chinese))