安哥拉罗安达湿陷性砂的载荷试验研究
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摘要
安哥拉罗安达广泛分布的湿陷性砂(Quelo砂),是一种对水十分敏感的特殊砂土,具有浸水后强度降低,并产生湿陷变形的特殊性质,由于缺乏相应的资料和工程经验,其湿陷程度和承载特性是评价的难点。本文通过天然和浸水饱和条件下的载荷试验,实测和研究了罗安达Quelo砂的湿陷变形特点和不同条件下的承载力特征。试验研究结果显示,罗安达Quelo砂是一种湿陷程度为轻微—中等的湿陷性土;Quelo砂的承载力对水分异常敏感,地基土含水率的微小变化即可导致承载力数倍的降低,且饱和后的承载力较小,试验场地浸水饱和后的地基承载力深度修正系数可取1.07。试验表明,在工程实践中考虑地基土含水率变化对地基承载力的影响,不采用消除地基全部湿陷量或部分湿陷量的方法,而将红砂地基当做一般地基进行设计是可行的。
The collapsible sand( Quelo sand),which occurs widely in Luanda of Angola,is sensitive to water content with the properties of soften and may causes collapsible deformation during soaking. Due to the lack of relevant data and engineering experience, it is difficult to evaluate the engineering properties of the collapsibility and bearing capacities. In this paper,the characteristics of the collapsible deformation and bearing capacities of Luanda Quelo sand are measured and studied by the plate load test( PLT) under the natural and soaking conditions. The experimental results show that the Quelo sand is a collapsible soil with slight to moderate collapsibility; the bearing capacity of the Quelo sand is sensitive to moisture. With the increasing moisture content of foundation soil,the bearing capacity will be reduced significantly with slight change in moisture and can make the bearing capacity several times lower than before during soaking. If the Quelo sand becomes saturated,the bearing capacity can be revised by the embedment depth with the coefficient of 1. 07 in the design of foundation. Thus,the foundation treatment,which according with theordinary design theory and using the bearing capacity value under the condition of subsoil moisture change,could conform to the requirements while construction without eliminating all collapse or partial collapse of subsoil.
The collapsible sand( Quelo sand),which occurs widely in Luanda of Angola,is sensitive to water content with the properties of soften and may causes collapsible deformation during soaking. Due to the lack of relevant data and engineering experience, it is difficult to evaluate the engineering properties of the collapsibility and bearing capacities. In this paper,the characteristics of the collapsible deformation and bearing capacities of Luanda Quelo sand are measured and studied by the plate load test( PLT) under the natural and soaking conditions. The experimental results show that the Quelo sand is a collapsible soil with slight to moderate collapsibility; the bearing capacity of the Quelo sand is sensitive to moisture. With the increasing moisture content of foundation soil,the bearing capacity will be reduced significantly with slight change in moisture and can make the bearing capacity several times lower than before during soaking. If the Quelo sand becomes saturated,the bearing capacity can be revised by the embedment depth with the coefficient of 1. 07 in the design of foundation. Thus,the foundation treatment,which according with theordinary design theory and using the bearing capacity value under the condition of subsoil moisture change,could conform to the requirements while construction without eliminating all collapse or partial collapse of subsoil.
引文
[1]Maria Luisa Putignano,Alessio Valente,AndréButa Neto.Carta geológica de Luanda(1:25000)[M].LUANDA:Departamento de geologia,Faculdade de ciências,Universidade Agostinho Neto,2000.(in Portuguese)
[2]Horta Da Silva J A,Gomes Teixeira J A P.Carta geotécnica da regi2o de Luanda-1.a aproximac2o[J].Técnica e Economia Ultramarinas,1973,11(2):91-100.(in Portuguese)
[3]刘争宏,廖燕宏,张玉守.罗安达砂物理力学性质初探[J].岩土力学,2010,31(增刊1):121-126.[LIU Z H,LIAO Y H,ZHANG Y S.Preliminary study of physic-mechanical properties of Luanda sand[J].Rock and Soil Mechanics,2010,31(Sup 1):121-126.(in Chinese)]
[4]孙宏伟,董勤,石峰.南部非洲红砂地基工程特性初探[J].建筑结构,2015,45(18):105-107.[SUN H W,DONG Q,SHI F.Preliminary discussion on geotechnical characteristics of red sand in southern Africa[J].Building Structure,2015,45(18):105-107.(in Chinese)]
[5]中华人民共和国建设部.GB 50021—2001岩土工程勘察规范[S].北京:中国建筑工业出版社,2009.[Ministry of Construction of the People’s Republic of China.GB 50021—2001 Code for investigation of geotechnical engineering[S].Beijing:China Architecture&Building Press,2009.(in Chinese)]
[6]中华人民共和国建设部.GB 50025—2004湿陷性黄土地区建筑规范[S].北京:中国建筑工业出版社,2004.[Ministry of Construction of the People’s Republic of China.GB 50025—2004 Code for building construction in collapsible loess regions[S].Beijing:China Architecture&Building Press,2004.(in Chinese)]
[7]张苏民,张炜.减湿和增湿时黄土的湿陷性[J].岩土工程学报,1992,14(1):57-61.[ZHANG S M,ZHANG W.The collapsibility of loess during moistening and drying processes[J].Chinese Journal of Geotechnical Engineering,1992,14(1):57-61.(in Chinese)]
[8]刘祖典.黄土力学与工程[M].西安:陕西科学技术出版社,1997.[LIU Z D.Mechanics and Engineering of Loess[M].Xi'an:Shaanxi Science and Technology Press,1997.(in Chinese)]
[9]刘彬,张庚成,李荣先.尼日尔风积砂土湿陷性试验研究与评价[J].中国海洋大学学报,2016,46(7):99-104.[LIU B,ZHANG G C,LI R X.Experimental study and evaluation on collapsibility of wind-blown sand in Niger[J].Periodical of Ocean University of China,2016,46(7):99-104.(in Chinese)]
[10]中华人民共和国建设部.GB 50007—2011建筑地基基础设计规范[S].北京:中国建筑工业出版社,2009.[Ministry of Construction of the People’s Republic of China.GB 50007—2011 Code for design of building foundation[S].Beijing:China Architecture&Building Press,2011.(in Chinese)]
[2]Horta Da Silva J A,Gomes Teixeira J A P.Carta geotécnica da regi2o de Luanda-1.a aproximac2o[J].Técnica e Economia Ultramarinas,1973,11(2):91-100.(in Portuguese)
[3]刘争宏,廖燕宏,张玉守.罗安达砂物理力学性质初探[J].岩土力学,2010,31(增刊1):121-126.[LIU Z H,LIAO Y H,ZHANG Y S.Preliminary study of physic-mechanical properties of Luanda sand[J].Rock and Soil Mechanics,2010,31(Sup 1):121-126.(in Chinese)]
[4]孙宏伟,董勤,石峰.南部非洲红砂地基工程特性初探[J].建筑结构,2015,45(18):105-107.[SUN H W,DONG Q,SHI F.Preliminary discussion on geotechnical characteristics of red sand in southern Africa[J].Building Structure,2015,45(18):105-107.(in Chinese)]
[5]中华人民共和国建设部.GB 50021—2001岩土工程勘察规范[S].北京:中国建筑工业出版社,2009.[Ministry of Construction of the People’s Republic of China.GB 50021—2001 Code for investigation of geotechnical engineering[S].Beijing:China Architecture&Building Press,2009.(in Chinese)]
[6]中华人民共和国建设部.GB 50025—2004湿陷性黄土地区建筑规范[S].北京:中国建筑工业出版社,2004.[Ministry of Construction of the People’s Republic of China.GB 50025—2004 Code for building construction in collapsible loess regions[S].Beijing:China Architecture&Building Press,2004.(in Chinese)]
[7]张苏民,张炜.减湿和增湿时黄土的湿陷性[J].岩土工程学报,1992,14(1):57-61.[ZHANG S M,ZHANG W.The collapsibility of loess during moistening and drying processes[J].Chinese Journal of Geotechnical Engineering,1992,14(1):57-61.(in Chinese)]
[8]刘祖典.黄土力学与工程[M].西安:陕西科学技术出版社,1997.[LIU Z D.Mechanics and Engineering of Loess[M].Xi'an:Shaanxi Science and Technology Press,1997.(in Chinese)]
[9]刘彬,张庚成,李荣先.尼日尔风积砂土湿陷性试验研究与评价[J].中国海洋大学学报,2016,46(7):99-104.[LIU B,ZHANG G C,LI R X.Experimental study and evaluation on collapsibility of wind-blown sand in Niger[J].Periodical of Ocean University of China,2016,46(7):99-104.(in Chinese)]
[10]中华人民共和国建设部.GB 50007—2011建筑地基基础设计规范[S].北京:中国建筑工业出版社,2009.[Ministry of Construction of the People’s Republic of China.GB 50007—2011 Code for design of building foundation[S].Beijing:China Architecture&Building Press,2011.(in Chinese)]