小型钢框架劲性水泥土挡墙的复合刚度研究
|
摘要
小型钢框架劲性水泥土挡墙在荷载作用下的工作机理尚未明确,且基坑工程涉及较多不确定因素,需要进行可靠度分析。开展集中荷载作用下悬臂梁试验,分析试件的荷载-型钢应力曲线、荷载-挠度曲线,确定试件的复合刚度代表点,考虑物理、几何、静力平衡三方面条件对代表点进行综合分析,提出试件的复合刚度计算方法。再结合实例,基于MATLAB进行刚度和稳定性方面的可靠度分析,利用蒙特卡洛法、JC法和窄界法等计算其在不同失效模式下的失效概率和系统失效概率。结果表明:1)复合刚度理论计算值与实测值相差14.29%;2)可靠度分析发现,倾覆破坏和顶部位移过大的失效概率较大,体系蒙特卡洛法所计算失效概率处于窄界法所计算失效概率范围内。提出的复合刚度计算方法能够为该支护结构刚度的可靠度分析提供依据,倾覆破坏和顶部位移过大是其主要失效模式。研究成果对于小型钢框架劲性水泥土挡墙的设计和应用具有一定的指导意义。
The soil mixing wall( SMW) is a supporting structure of foundation pit to provide major structural bearing capacity,composing of cement-soil and large steel. In traditional SMW,the contribution of cement-soil is neglected by design methods and the cost of large steel column is expensive. Therefore the small steel frame rigid cement-soil retaining wall has been explored to replace individual large steel columns in the SMW with small steel frames,and correlational researches have developed extensively. However,the working mechanism of small steel frame rigid cementsoil retaining wall under loads was unclear in the past decades. In addition,the foundation pit engineering includes various uncertainties,so the reliability analysis on the supporting structure is also in great urgent. In this study,experiments regarding cantilever beam under concentrated loads were firstly carried out and load-steel stress curve as well as load-deformation curve of specimen were analyzed. Secondly,based on the representative points of specimen composite stiffness,a new calculation method of composite stiffness on the supporting structure was proposed from aspects of physics,geometry as well as statics balance. Thirdly,the reliability analysis on stiffness and stability was implemented to calculate the systematic failure probability by using Monte-Carlo method,JC method,and narrow boundary method by MATLAB. The results showed that the calculated composite stiffness value of 14.29% was lower than the measured one. Besides,the results of the reliability analysis showed that there was considerable failure probability of overturning and excessive displacement on the specimen top. The failure probability calculated by systematic Monte-Carlo method was within the range of narrow bound method. Moreover,the calculation method of composite stiffness can be employed to execute the reliability analysis of supporting structure stiffness and to prove that overturning and excessive displacements of the top are the main failure modes. In conclusion,the results of this study can be utilized to make positive contributions to the design and application of small steel frame rigid cement-soil retaining wall.
The soil mixing wall( SMW) is a supporting structure of foundation pit to provide major structural bearing capacity,composing of cement-soil and large steel. In traditional SMW,the contribution of cement-soil is neglected by design methods and the cost of large steel column is expensive. Therefore the small steel frame rigid cement-soil retaining wall has been explored to replace individual large steel columns in the SMW with small steel frames,and correlational researches have developed extensively. However,the working mechanism of small steel frame rigid cementsoil retaining wall under loads was unclear in the past decades. In addition,the foundation pit engineering includes various uncertainties,so the reliability analysis on the supporting structure is also in great urgent. In this study,experiments regarding cantilever beam under concentrated loads were firstly carried out and load-steel stress curve as well as load-deformation curve of specimen were analyzed. Secondly,based on the representative points of specimen composite stiffness,a new calculation method of composite stiffness on the supporting structure was proposed from aspects of physics,geometry as well as statics balance. Thirdly,the reliability analysis on stiffness and stability was implemented to calculate the systematic failure probability by using Monte-Carlo method,JC method,and narrow boundary method by MATLAB. The results showed that the calculated composite stiffness value of 14.29% was lower than the measured one. Besides,the results of the reliability analysis showed that there was considerable failure probability of overturning and excessive displacement on the specimen top. The failure probability calculated by systematic Monte-Carlo method was within the range of narrow bound method. Moreover,the calculation method of composite stiffness can be employed to execute the reliability analysis of supporting structure stiffness and to prove that overturning and excessive displacements of the top are the main failure modes. In conclusion,the results of this study can be utilized to make positive contributions to the design and application of small steel frame rigid cement-soil retaining wall.
引文
[1]郑刚,张华.型钢水泥土复合梁中型钢-水泥土相互作用试验研究[J].岩土力学,2007,28(5):939-943,950.ZHENG G,ZHANG H.Experimental study of interaction between cemented soil and shape steel of shaped steel reinforced cemented soil composite beam[J].Rock and Soil Mechanics,2007,28(5):939-943,950.
[2]杨平,曹宝飞,尹鹏,等.小刚度劲性水泥土墙基坑支护的机理及模型试验[J].南京林业大学学报(自然科学版),2007,31(3):19-24.YANG P,CAO B F,YIN P,et al.An experimental study of models on small H-steel soil-cement wall foundation pit bracing mechanism[J].Journal of Nanjing Forestry University(Natural Sciences Edition),2007,31(3):19-24.
[3]孔德志,张庆贺,宋杰.劲性水泥土连续墙的抗弯刚度研究[J].岩石力学与工程学报,2004,23(11):1935-1938.KONG D Z,ZHANG Q H,SONG J.Study on bending stiffness of reinforced continuous cement-soil wall[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(11):1935-1938.
[4]高大钊.土力学可靠性原理[M].北京:中国建筑工业出版社,1989.
[5]LUMB P.Soil variable and engineering design[C]//VALLIAPPAN S,HAINS.LEE I K,eds.Soil Mechanics Recent Developments-Proc of the General Session of the Symposium Held at the University of New South Wales.Australia,1975:383-397.
[6]ANG A H S,CORNELL C A.Reliability bases of structural safety and design[J].Journal of Structural Division,1974,100(ST9):1755-1769.
[7]孙长宁,曹净,宋志刚,等.基坑体系可靠度的条件概率计算方法[J].岩土力学,2014,35(4):1211-1216.SUN C N,CAO J,SONG Z G,et al.Calculation method of foundation pit system reliability based on conditional probability[J].Rock and Soil Mechanics,2014,35(4):1211-1216.
[8]黄灵芝,司政,杜占科.基于JC法的重力坝深层抗滑稳定研究[J].西北农林科技大学学报(自然科学版),2015,43(3):229-234.HUANG L Z,SI Z,DU Z K.JC method based deep anti-sliding stability of gravity dam[J].Journal of Northwest A&F University(Natural Science Edition),2015,43(3):229-234.
[9]秦高峰,李镜培,刘陕南,等.上海软土基坑板式支护结构稳定性可靠度分析[J].岩土工程学报,2013,35(S2):532-536.QIN G F,LI J P,LIU S N,et al.Reliability of flexible retaining structure of excavations in Shanghai soft soils[J].Chinese Journal of Geotechnical Engineering,2013,35(S2):532-536.
[10]杨林德,徐超.Monte Carlo模拟法与基坑变形的可靠度分析[J].岩土力学,1999,20(1):16-19.YANG L D,XU C.Monte Carlo simulation and reliability analysis on the deformation of foundation pit[J].Rock and Soil Mechanics,1999,20(1):16-19.
[11]杜永峰,余钰,李慧.重力式挡土墙稳定性的结构体系可靠度分析[J].岩土工程学报,2008,30(3):349-353.DU Y F,YU Y,LI H.Analysis of reliability of structural systems for stability of gravity retaining walls[J].Chinese Journal of Geotechnical Engineering,2008,30(3):349-353.
[12]王建华.基坑支护体系稳定可靠度分析[J].水力发电,2008,34(3):52-54.WANG J H.Reliability analysis of stability for braced structures of excavation[J].Water Power,2008,34(3):52-54.
[13]TAN Q M.Dimensional analysis:with case studies in mechanics[M].Heidelberg:Springer Science&Business Media,2011:14-15.
[14]刘一林.水泥搅拌桩复合地基变形特性研究[D].杭州:浙江大学,1990.LIU Y L.Study on deformation of composite foundation with cement-soil mixed piles[D].Hangzhou:Zhejiang University,1990.
[15]管义安.深基坑工程设计施工中技术难点分析与工程实践[D].厦门:厦门大学,2009.GUAN Y A.The analysis of technical difficulty and project practice in foundation pitdesign and construction[D].Xiamen:Xiamen University,2009.
[16]高谦,吴顺川,万林海.土木工程可靠性理论及其应用[M].北京:中国建材工业出版社,2007.
[17]侯晓亮,谭晓慧.改进的一次二阶矩方法在基坑抗隆起稳定可靠度评价中的应用[J].武汉大学学报(工学版),2016,49(5):791-795.HOU X L,TAN X H.Application of advanced first order second moment method to reliability assessment of basal heave stability for braced excavation[J].Engineering Journal of Wuhan University,2016,49(5):791-795.
[18]周景星,李广信,虞石民,等.基础工程[M].北京:清华大学出版社,2007.
[2]杨平,曹宝飞,尹鹏,等.小刚度劲性水泥土墙基坑支护的机理及模型试验[J].南京林业大学学报(自然科学版),2007,31(3):19-24.YANG P,CAO B F,YIN P,et al.An experimental study of models on small H-steel soil-cement wall foundation pit bracing mechanism[J].Journal of Nanjing Forestry University(Natural Sciences Edition),2007,31(3):19-24.
[3]孔德志,张庆贺,宋杰.劲性水泥土连续墙的抗弯刚度研究[J].岩石力学与工程学报,2004,23(11):1935-1938.KONG D Z,ZHANG Q H,SONG J.Study on bending stiffness of reinforced continuous cement-soil wall[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(11):1935-1938.
[4]高大钊.土力学可靠性原理[M].北京:中国建筑工业出版社,1989.
[5]LUMB P.Soil variable and engineering design[C]//VALLIAPPAN S,HAINS.LEE I K,eds.Soil Mechanics Recent Developments-Proc of the General Session of the Symposium Held at the University of New South Wales.Australia,1975:383-397.
[6]ANG A H S,CORNELL C A.Reliability bases of structural safety and design[J].Journal of Structural Division,1974,100(ST9):1755-1769.
[7]孙长宁,曹净,宋志刚,等.基坑体系可靠度的条件概率计算方法[J].岩土力学,2014,35(4):1211-1216.SUN C N,CAO J,SONG Z G,et al.Calculation method of foundation pit system reliability based on conditional probability[J].Rock and Soil Mechanics,2014,35(4):1211-1216.
[8]黄灵芝,司政,杜占科.基于JC法的重力坝深层抗滑稳定研究[J].西北农林科技大学学报(自然科学版),2015,43(3):229-234.HUANG L Z,SI Z,DU Z K.JC method based deep anti-sliding stability of gravity dam[J].Journal of Northwest A&F University(Natural Science Edition),2015,43(3):229-234.
[9]秦高峰,李镜培,刘陕南,等.上海软土基坑板式支护结构稳定性可靠度分析[J].岩土工程学报,2013,35(S2):532-536.QIN G F,LI J P,LIU S N,et al.Reliability of flexible retaining structure of excavations in Shanghai soft soils[J].Chinese Journal of Geotechnical Engineering,2013,35(S2):532-536.
[10]杨林德,徐超.Monte Carlo模拟法与基坑变形的可靠度分析[J].岩土力学,1999,20(1):16-19.YANG L D,XU C.Monte Carlo simulation and reliability analysis on the deformation of foundation pit[J].Rock and Soil Mechanics,1999,20(1):16-19.
[11]杜永峰,余钰,李慧.重力式挡土墙稳定性的结构体系可靠度分析[J].岩土工程学报,2008,30(3):349-353.DU Y F,YU Y,LI H.Analysis of reliability of structural systems for stability of gravity retaining walls[J].Chinese Journal of Geotechnical Engineering,2008,30(3):349-353.
[12]王建华.基坑支护体系稳定可靠度分析[J].水力发电,2008,34(3):52-54.WANG J H.Reliability analysis of stability for braced structures of excavation[J].Water Power,2008,34(3):52-54.
[13]TAN Q M.Dimensional analysis:with case studies in mechanics[M].Heidelberg:Springer Science&Business Media,2011:14-15.
[14]刘一林.水泥搅拌桩复合地基变形特性研究[D].杭州:浙江大学,1990.LIU Y L.Study on deformation of composite foundation with cement-soil mixed piles[D].Hangzhou:Zhejiang University,1990.
[15]管义安.深基坑工程设计施工中技术难点分析与工程实践[D].厦门:厦门大学,2009.GUAN Y A.The analysis of technical difficulty and project practice in foundation pitdesign and construction[D].Xiamen:Xiamen University,2009.
[16]高谦,吴顺川,万林海.土木工程可靠性理论及其应用[M].北京:中国建材工业出版社,2007.
[17]侯晓亮,谭晓慧.改进的一次二阶矩方法在基坑抗隆起稳定可靠度评价中的应用[J].武汉大学学报(工学版),2016,49(5):791-795.HOU X L,TAN X H.Application of advanced first order second moment method to reliability assessment of basal heave stability for braced excavation[J].Engineering Journal of Wuhan University,2016,49(5):791-795.
[18]周景星,李广信,虞石民,等.基础工程[M].北京:清华大学出版社,2007.