基于柔性承载板载荷试验的土抗剪强度参数反演研究
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摘要
传统的刚性承载板载荷试验(PLT)主要确定地基的承载力,不能用来反演土的抗剪强度参数c、j。通过刚性承载板下加装气囊,研制出一种适用于载荷试验的柔性承载板,两个电感式位移传感器分别布置于板内边缘处,用于测量该处气囊厚度变化量dδ。用柔性承载板开展载荷试验时板底压力P均匀分布,同时在柔性承载板一侧采用柔性水压板施加恒定的均匀地表荷载,根据两条p-dδ曲线变化规律得出2个临塑荷载,将临塑荷载与地表荷载值代入理论公式反演出c、j。分别采用黏性土和干砂开展室内载荷试验,证明了该反演方法的可行性,通过分析认为该反演方法具有适用性和先进性。
The traditional rigid bearing plate load test(PLT) mainly determines the bearing capacity of foundation, and can not be used to invert the shear strength parameters c, j. In this study a flexible bearing plate has been invented through the installation of an air bag under the rigid bearing plate. Two self-made inductance displacement sensor are respectively set at the edge of two inner sides of the plate, in order to measure the variation of the thickness of the air bag at this area. When the flexible bearing plate is used to carried out the loading test, the compressive stress p under the plate is in uniform distribution. During the test, a constant uniform surface load q is applied on one side of the bearing plate by a flexible water pressure plate. So that two p-dδ curves can be got, and two critical edge load values can be judged from the curves' changing feature corresponding to zero surface load and q respectively. Then the c and j can be inversed if we put the critical edge load values and q into the theoretical formula. The cohesive soil and dry sand have been tested respectively during the laboratory experiments; and the feasibility of the inversion method is proved. The applicability and the progressiveness of the inversion method are also approved through analysis.
The traditional rigid bearing plate load test(PLT) mainly determines the bearing capacity of foundation, and can not be used to invert the shear strength parameters c, j. In this study a flexible bearing plate has been invented through the installation of an air bag under the rigid bearing plate. Two self-made inductance displacement sensor are respectively set at the edge of two inner sides of the plate, in order to measure the variation of the thickness of the air bag at this area. When the flexible bearing plate is used to carried out the loading test, the compressive stress p under the plate is in uniform distribution. During the test, a constant uniform surface load q is applied on one side of the bearing plate by a flexible water pressure plate. So that two p-dδ curves can be got, and two critical edge load values can be judged from the curves' changing feature corresponding to zero surface load and q respectively. Then the c and j can be inversed if we put the critical edge load values and q into the theoretical formula. The cohesive soil and dry sand have been tested respectively during the laboratory experiments; and the feasibility of the inversion method is proved. The applicability and the progressiveness of the inversion method are also approved through analysis.
引文
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[14]谢新宇,韩冬冬,黄利,等.粗糙条形基础极限承载力系数Nr的计算[J].岩土力学,2016,37(增刊1):209-214.XIE Xin-yu,HAN Dong-dong,HUANG Li,et al.Calculation of ultimate bearing capacity factor Nr for rough strip footings[J].Rock and Soil Mechanics,2010,29(Supp.2):3728-3734.
[15]杨小伟,许年春,尹一,等.电感式位移传感器在柔性承载板载荷试验中的应用[J].山西建筑,2014,40(16):56-58.YANG Xiao-wei,XU Nian-chun,YIN Yi,et al.The application of inductive displacement sensor in flexible bearing plate load test[J].Shanxi Architecture,2014,40(16):56-58.
[16]XU Nian-chun,XIA Wen-jing,WU Tong-qing.The effect of friction at the strip footings’underside on the expansion of plastic zones in subgrade[J].Advanced Materials Research,2014,(1008-1009):1227-1233.
[17]张玉伟.斜陡边坡前缘挡墙主动土压力计算方法研究[硕士学位论文D].重庆:重庆交通大学,2017.ZHANG Yu-wei.The study of the calculation method of active earth pressure on retaining wall of inclined steep slope[M.S.Thesis D].Chongqing:Chongqing Jiaotong University,2017.
[18]许年春,吴同情,冯桥木,等.土变形模量的柔性承载板测试研究[J].岩土力学,2017,38(增刊1):496-450.XU Nian-chun,WU Tong-qing,FENG Qiao-mu,et al.The research on the test of soil’s deformation modulus using flexible bearing plate[J].Rock and Soil Mechanics,2017,38(Supp.1):496-450.
[2]建设综合勘察设计院有限公司.GB 50021-2001岩土工程勘察规范[S].北京:中国建筑工业出版社,2015.GIGIS(China)Ltd.,GB 50021-2001 Code for geotechnical engineering investigation[S].Beijing:China Architecture&Building Press,2015.
[3]闫澍旺,封晓伟,侯晋芳,等.用十字板强度推算软黏土抗剪强度指标的方法及应用[J].岩土工程学报,2009,31(12):1805-1810.YAN Shu-wang,FENG Xiao-wei,HOU Jin-fang,et al.Deduction and application of strength parameters of soft clay by use of vane strength[J].Chinese Journal of Geotechnical Engineering,2009,31(12):1805-1810.
[4]闫澍旺,孙立强,李伟,等.真空加固超软土工艺的室内模型试验研究[J].岩土工程学报,2011,33(3):341-347.YAN Shu-wang,SUN Li-qiang,LI Wei,et al.Model test on vacuum preloading technology of super-soft soil[J].Chinese Journal of Geotechnical Engineering,2011,33(3):341-347.
[5]郭喜峰,晏鄂川,刘洋.三峡库区碎石土滑坡体抗剪强度研究[J].重庆交通大学学报(自然科学版),2015,34(1):68-71.GUO Xi-feng,YAN E'–chuan,LIU Yang.Shear strength of gravel soil landsilde in the Three Gorges reservoir zone[J].Journal of Chongqing Jiaotong University(Natural Science),2015,34(1):68-71.
[6]李东升,刘东升.固结煤矸石抗剪强度特征试验[J].重庆大学学报,2015,38(3):59-66.LI Dong-sheng,LIU Dong-sheng.Experimental research on the shear strength of consolidation gangue[J].Journal of Chongqing University,2015,38(3):58-65.
[7]吴珺华,袁俊平.干湿循环下膨胀土现场大型剪切试验研究[J].岩土工程学报,2013,35(增刊1):103-107.WU Jun-hua,YUAN Jun-ping.Field tests on expansive soil during wetting-drying cycles using large shear apparatus[J].Chinese Journal of Geotechnical Engineering,2013,35(Supp.1):103-107.
[8]陈晓平.土力学与基础工程[M].北京:水利水电出版社,2008.CHEN Xiao-ping.Soil mechanics and foundation engineering[M].Beijing:Hydraulic and Electric Power Press,2008.
[9]赵明阶.土力学与地基基础[M].北京:人民交通出版社,2009.ZHAO Ming-jie.Soil mechanics and foundation[M].Beijing:China Communications Press,2009.
[10]洪毓康.土质学与土力学(第二版)[M].北京:人民交通出版社,2011.HONG Yu-kang.Soil science and soil mechanics(2nd ed)[M].Beijing:China Communications Press,2011.
[11]ZHANG Ke,CAO Ping,BAO Rui.Rigorous back analysis of shear strength parameters of landslide slip[J].Transactions of Nonferrous Metals Society of China,2013,23(5):1459-1464.
[12]石崇,张玉,孙怀昆,等.争岗滑坡堆积体滑面强度参数反演分析[J].岩石力学与工程学报,2010,29(增刊2):3728-3734.SHI Chong,ZHANG Yu,SUN Huai-kun,et al.Back analysis of strength parameters of sliding surface of Zhenggang landslide deposit body[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(Supp.2):3728-3734.
[13]周小平,黄煜镔,丁志诚.考虑中间主应力的太沙基地基极限承载力公式[J].岩石力学与工程学报,2002,21(10):1554-1556.ZHOU Xiao-ping,HUANG Yu-bin,DING Zhi-cheng.Influence of intermediate principal stress on the formula of Terzaghi ultimate bearing capacity of foundations[J].Chinese Journal of Rock Mechanics and Engineering,2002,21(10):1554-1556.
[14]谢新宇,韩冬冬,黄利,等.粗糙条形基础极限承载力系数Nr的计算[J].岩土力学,2016,37(增刊1):209-214.XIE Xin-yu,HAN Dong-dong,HUANG Li,et al.Calculation of ultimate bearing capacity factor Nr for rough strip footings[J].Rock and Soil Mechanics,2010,29(Supp.2):3728-3734.
[15]杨小伟,许年春,尹一,等.电感式位移传感器在柔性承载板载荷试验中的应用[J].山西建筑,2014,40(16):56-58.YANG Xiao-wei,XU Nian-chun,YIN Yi,et al.The application of inductive displacement sensor in flexible bearing plate load test[J].Shanxi Architecture,2014,40(16):56-58.
[16]XU Nian-chun,XIA Wen-jing,WU Tong-qing.The effect of friction at the strip footings’underside on the expansion of plastic zones in subgrade[J].Advanced Materials Research,2014,(1008-1009):1227-1233.
[17]张玉伟.斜陡边坡前缘挡墙主动土压力计算方法研究[硕士学位论文D].重庆:重庆交通大学,2017.ZHANG Yu-wei.The study of the calculation method of active earth pressure on retaining wall of inclined steep slope[M.S.Thesis D].Chongqing:Chongqing Jiaotong University,2017.
[18]许年春,吴同情,冯桥木,等.土变形模量的柔性承载板测试研究[J].岩土力学,2017,38(增刊1):496-450.XU Nian-chun,WU Tong-qing,FENG Qiao-mu,et al.The research on the test of soil’s deformation modulus using flexible bearing plate[J].Rock and Soil Mechanics,2017,38(Supp.1):496-450.