钢筋混凝土结构在地基土冻胀中的结构受力分析和防治研究
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摘要
地基土冻胀对建筑物的基础会产生水平冻胀力、切向冻胀力、法向冻胀力,使建筑物的基础倾斜、挠曲、拔起、损坏,严重影响地面建筑物,导致地面建筑物位移过大、局部破坏、倾倒、产生过大裂缝而不能正常使用。我国960万平方公里的土地上,冻土区分布极为广阔,若包括冻结深度大于0.5米的季节性冻土区在内,其面积约占全国总面积的68.6%,其中多年冻土面积约占全国领土面积的22.3%。在冻土地区和多年冻土地区修建各种工程建筑物,常由于地基土冻胀而使建筑物破坏,造成经济损失。因此,研究地基土冻胀对建筑物基础的作用及防治措施具有极其重大意义。世界各国在50年代就开始了对冻土的研究,我国在80年代对冻土的研究才有所进展,但由于引起土体冻胀的因素颇多,自然条件下的地基土情况复杂,冻胀产生的效应就更加多变,因此到目前为止,对冻土的各种现象、规律、土的冻胀性评价、冻胀力的取值标准、冻胀力的理论计算方法、冻胀力的工程预报、防止冻胀破坏的措施,特别是一些取决于自然因素的定量评价还存在着不足和局限性,使得我国建筑设计规范中对冻土区的建筑物基础设计规定只有极少的内容。本文总结了当前冻土研究的新进展、引起土体冻胀量大小的诸因素、冻胀产生的力学效应、防止冻胀破坏的措施这些方面的经验。在冻胀产生的力学效应方面,尤其是冻胀反力的理论计算方面提出了新的计算方法。本文把地基土看作双层地基,当冻深等于扩大式基础顶面埋深时,将冻胀反应力简化成三角形分布,推导出了扩大式桩和条形基础上的冻胀反力的计算公式。当扩大式基础顶面埋深大于冻深一定厚度时,把地基土看作均质各向同性的半无限直线变形体,运用弹性力学中的布希涅斯克公式和费拉曼公式计算出了扩大式桩基础和条形基础的冻胀反力计算公式。为简化计算,用最小二乘法推导出了用直线代替曲线的方法,用该方法将冻胀反力的曲线形应力分布图形简化成分段直线分布的应力图形。该直线替代法得出的结果,与其他研究者用逼近法得出的结果相比,误差最小。同时考虑基础侧壁与未冻土之间的摩擦,将冻胀反力的应力分布图形,简化成鞍形应力分布图形,并推导出了计算公式。该应力的分布形式与科研单位实测的应力分布形式一致,这样从理论上解决了冻胀反力在扩大式桩和条形基础上的分布及计算问题。本方法适用于季节冻土地区对桩和条形基础的受力分析计算,也可作为工程设计人员在进行桩和条形基础的设计时,考虑基础锚固力的分析计算方法。本文还根据引起冻胀的因素,对防止冻胀破坏的措施进行了归纳和总结,以便工程技术人员和设计人员参考运用。
The swellingground will produce the horizontal frost heaving pressure, the tangential frost heaving pressure, the normal frost heaving pressure to building's foundation. So that the basic building tilted, flexed, uprooted, damaged, seriously affecting ground-level structures, resulting in too large displacement of ground-level structures, the serious incline, the partial destruction, leading to produce the oversized crack, and cannot use normally. On our country 9,600,000 square kilometers lands, the frozen earth area distribution is extremely broad, If we include the freezing of the depth of earth greater than 0.5 meters in the seasonal frozen earth region , its area approximately composes the national total area 68.6%, Permafrost area in which the national territory, an area of about 22.3%. Construct each kind of engineering structures in the frozen earth area and permafrost area, often as a result of swellingground damage caused to the buildings, causing economic losses. Therefore, the study of the harm and the prevention measure of swellingground to the buildings has great significance. Various countries started the frozen earth research in the 50s, Chinese research on permafrost in the 80's began to progress, However, due to swellingground caused by many factors, under natural condition's foundation soil situation is complex, the effects of frost heaving is more changeable. Therefore so far, On the phenomena of the permafrost, the rule, the earth heave appraisal, the frost heaving pressure value standard, the frost heaving pressure theoretical calculation method, the frost heave prediction power projects, the measures to prevent frost heave damage, specially some are decided by the natural factor quantitative evaluation also have the insufficiency and the limitation, which causes in our country's architectural design specification of the buildings in permafrost regions on the basis of design requirements that only a very small content. This article summarized the new progress of current frozen earth research, the factors of soil heaving caused by the volume size, the mechanical effects of frost heave, measures to prevent frost-heaving damage, and such experience in these areas. Resulting in frost heave mechanical effects, particularly the heave reaction's theoretical calculation aspect proposed the new computational method. This article regards the foundation soil as the double-decked ground, when the frozen of deep foundation equivalent to the expansion of the top surface depth, Inferred in the derived extended piling wall frost heave on the basis of the formula for calculating the reaction force. When the burying depth of the top of expanded type foundation is bigger than the frozen deep certain thickness, regards the foundation soil as a homogeneous isotropic semi-infinite linear deformation body. The use of elasticity in the Boussinesq formula and the Furameru formula to calculate the formula of extended pile foundation and frost heaving reaction of wall foundation. To simplify the calculation, inferred with the least squares method has replaced the curve with the straight line the method. Ways will be heaving with the anti-power-shaped stress distribution curve graphic components to simplify the stress distribution above a straight line graph. This straight line substitution method obtains the result, the result which obtains with the approximation compares with other researchers, the error is smallest. Taking into account the foundation wall with no friction between the permafrost, anti-frost heaving force will stress distribution graphics, simplified into a saddle-shaped stress distribution graph, and derived a formula for calculating. Stress distribution of the forms and scientific research units of the stress distribution in the form of measured and consistent, and theoretically solved heaving reaction force in the extended pile wall on the basis of the distribution and calculation. The method is applicable to seasonal permafrost regions of the foundation pile wall stress analysis calculations. It can also be used as engineering design staff in the design of pile foundation walls, considering the analysis of basic anchoring force calculation. This article also acts according to factor of frost heaving, summarizes and sums up measures to prevent frost heave damage, so that the engineers and technicians and the designers could refer to.
The swellingground will produce the horizontal frost heaving pressure, the tangential frost heaving pressure, the normal frost heaving pressure to building's foundation. So that the basic building tilted, flexed, uprooted, damaged, seriously affecting ground-level structures, resulting in too large displacement of ground-level structures, the serious incline, the partial destruction, leading to produce the oversized crack, and cannot use normally. On our country 9,600,000 square kilometers lands, the frozen earth area distribution is extremely broad, If we include the freezing of the depth of earth greater than 0.5 meters in the seasonal frozen earth region , its area approximately composes the national total area 68.6%, Permafrost area in which the national territory, an area of about 22.3%. Construct each kind of engineering structures in the frozen earth area and permafrost area, often as a result of swellingground damage caused to the buildings, causing economic losses. Therefore, the study of the harm and the prevention measure of swellingground to the buildings has great significance. Various countries started the frozen earth research in the 50s, Chinese research on permafrost in the 80's began to progress, However, due to swellingground caused by many factors, under natural condition's foundation soil situation is complex, the effects of frost heaving is more changeable. Therefore so far, On the phenomena of the permafrost, the rule, the earth heave appraisal, the frost heaving pressure value standard, the frost heaving pressure theoretical calculation method, the frost heave prediction power projects, the measures to prevent frost heave damage, specially some are decided by the natural factor quantitative evaluation also have the insufficiency and the limitation, which causes in our country's architectural design specification of the buildings in permafrost regions on the basis of design requirements that only a very small content. This article summarized the new progress of current frozen earth research, the factors of soil heaving caused by the volume size, the mechanical effects of frost heave, measures to prevent frost-heaving damage, and such experience in these areas. Resulting in frost heave mechanical effects, particularly the heave reaction's theoretical calculation aspect proposed the new computational method. This article regards the foundation soil as the double-decked ground, when the frozen of deep foundation equivalent to the expansion of the top surface depth, Inferred in the derived extended piling wall frost heave on the basis of the formula for calculating the reaction force. When the burying depth of the top of expanded type foundation is bigger than the frozen deep certain thickness, regards the foundation soil as a homogeneous isotropic semi-infinite linear deformation body. The use of elasticity in the Boussinesq formula and the Furameru formula to calculate the formula of extended pile foundation and frost heaving reaction of wall foundation. To simplify the calculation, inferred with the least squares method has replaced the curve with the straight line the method. Ways will be heaving with the anti-power-shaped stress distribution curve graphic components to simplify the stress distribution above a straight line graph. This straight line substitution method obtains the result, the result which obtains with the approximation compares with other researchers, the error is smallest. Taking into account the foundation wall with no friction between the permafrost, anti-frost heaving force will stress distribution graphics, simplified into a saddle-shaped stress distribution graph, and derived a formula for calculating. Stress distribution of the forms and scientific research units of the stress distribution in the form of measured and consistent, and theoretically solved heaving reaction force in the extended pile wall on the basis of the distribution and calculation. The method is applicable to seasonal permafrost regions of the foundation pile wall stress analysis calculations. It can also be used as engineering design staff in the design of pile foundation walls, considering the analysis of basic anchoring force calculation. This article also acts according to factor of frost heaving, summarizes and sums up measures to prevent frost heave damage, so that the engineers and technicians and the designers could refer to.
引文
[1]徐学祖,何平,张建明.土体冻结和冻胀研究的新进展[J].冰川冻土,1997,19(3):280—283.
[2]程国栋,马巍.国际冻土工程研究进展[J].冰川冻土,2003,25(3): 303—308. [3 ]隋咸志,左力.冻胀反力的实验研究[J].冰川冻土,1983,5(2):19—28. [4 ]戴惠民,田德廷,雍致盛.公路桥梁钢筋混凝土桩切向冻胀力的研究[J].公路,1986,(10):16—25.
[5]刘鸿绪.对土冻结过程中若干冻胀力学问题得商榷[J]..冰川冻土,1990,12[3]:269—280.
[6]刘鸿绪.对切向冻胀力沿桩侧表面分布的探讨[J].冰川冻土,1993,15(2):289—292.
[7]隋超,刘琪,郑虹.切向冻胀力作用下基础锚固并兼评“冻胀反力”问题[J].低温建筑技术,1997,(2):39—40.
[8]祝国林,张玉富,刘福生.季节性冻土切向冻胀力与冻胀性关系[J].黑龙江交通科技,2005,(9):83—84.
[9] JGJ118—98,冻土地区建筑地基基础设计规范[S].北京:中国建筑工业出版社,1998.
[10] GB50007—2002,建筑地基基础设计规范[S].北京:中国建筑工业出版社,2002.
[11]童长江,管枫年..土的冻胀与建筑物冻害防治[M].北京:水利电力出版社,1985:3—3
[12] Hanley,T.O'D.,Rao,S.R..Electrical freezing potentials and the migration of moisture and ions in freezing soils.“Abstracts”,Fourth Canadian Permafrost Conferegce 1981.
[13]柯洁铭.人工冻土冻胀数值模拟分析[D].南京:南京林业大学,2004.
[14]吴紫汪.土的冻胀性实验研究[G].中国科学院兰州冰川冻土研究所集刊,科学出版,1981.
[15] Johnson,T.C.,Berg,R.L..Roadway design in seasonal frost areas.CRREL Tech.Rept.259.1975.
[16]谢音琦.用压实土做防冻胀地基的探讨[R].抗冻技术情报. 1980,(2).
[17] Wang Mianchang . Frost behaviour of compacted soil . Higway Res.Rec.No.360 .1971.
[18] Takashi,T..Effect of penetration rate of freezing and confining stress on the frost heave ratio of soil.Proc .3rd Int'1.Conf.Permafrost.1978.
[19] Penner , E..Influence of freezing rate on frost heaving.Highway Res.Rec.No.393.1972.
[20] Aitken,G.W..Reduction of frost heave by surcharge stress.CRREL,TR 184.1974.
[21] kaplar,C.W..Freezing test for evaulating relative frost susceptibility of various soil CRREL.TR 250.1974.
[22] Arvidson , W . D ., Morgenstern , N . R .. Water flow induced by soils freezing. Can.Geotech.J.Vol.14,No.2.1977.
[23] Penner,E.and walton,T..Effects of temperature and pressure on frost heaving. Eng.Geol.Vol.13,No.1-4.1979.
[24]吴紫汪,张家懿.冻土融化压力的初步试验[G].青藏冻土研究论文集,北京:科学出版社,1983.
[25] Yong,R.N..Prediction of salt influence on unfrozen water content in frozen soils Engineering Geology Jounal Vol.13,No.1-4.1979
[26]吴紫汪.土冻结时对基础的切向冻胀力实验研究[G].中国科学院兰州冰川冻土研究所集刊,1981.
[27]周长庆.我国冻土地基基础研究成就概述[J].冰川冻土,1980,2(1).
[28]丁靖康.切向冻胀力的野外试验研究[G].第二届全国冻土学术会议论文选集,兰州:甘肃人民出版社,1983.
[29]童长江.基础的冻胀力[G].中国地理学会冰川冻土学术会议论文选集,北京:科学出版社,1982.
[30]吴紫汪.基础与冻土间冻结强度的试验研究[G].中国科学院兰州冰川冻土研究所集刊,北京:科学出版社,1981.
[31]陈肖柏,刘建坤,刘鸿绪.土的冻结作用与地基[M].北京:科学出版社,2006:222
[32]童长江.风火山多年冻土区季节融化层冻结时的法向冻胀力[G].青藏冻土研究论文集,北京:科学出版社,1983.
[33]武汉水利电力学院..水利工程管理[M].北京:水利电力出版社,1990:144—149.
[34]隋咸志.季节冻土区扩大式基础上冻胀反力的计算[J].冰川冻土,1985,7(3):213—220.
[35]中华人民共和国交通部.公路桥梁设计规范[S].北京:人民交通出版社,1995.
[36]赵国逵,苗青.土的冻胀对建筑物的危害与防治[J].低温建筑技术,2001,(3),72—73.
[37]裴章勤,卢继清.国内外物理化学方法防治土体冻胀的研究[J].冰川冻土,1982,4(1).
[38]铁道科学院金化所,天津师范学院化学系.表面活性剂在铁路路基化学防冻胀中的应用研究[G].铁道科学技术公务工程手册,1978.
[39]管枫年.板基法向冻胀力现场试验研究[J].冰川冻土,1981,3(3).
[40]王希尧.水工板式衬砌体的允许冻胀变位和冻胀量估算[J].抗冻技术情报,1983,(2).
[41]周有才.两种刚性基础防冻害效果的对比[G].中国科学院兰州冰川冻土研究所集刊,北京:科学出版社,1990.
[2]程国栋,马巍.国际冻土工程研究进展[J].冰川冻土,2003,25(3): 303—308. [3 ]隋咸志,左力.冻胀反力的实验研究[J].冰川冻土,1983,5(2):19—28. [4 ]戴惠民,田德廷,雍致盛.公路桥梁钢筋混凝土桩切向冻胀力的研究[J].公路,1986,(10):16—25.
[5]刘鸿绪.对土冻结过程中若干冻胀力学问题得商榷[J]..冰川冻土,1990,12[3]:269—280.
[6]刘鸿绪.对切向冻胀力沿桩侧表面分布的探讨[J].冰川冻土,1993,15(2):289—292.
[7]隋超,刘琪,郑虹.切向冻胀力作用下基础锚固并兼评“冻胀反力”问题[J].低温建筑技术,1997,(2):39—40.
[8]祝国林,张玉富,刘福生.季节性冻土切向冻胀力与冻胀性关系[J].黑龙江交通科技,2005,(9):83—84.
[9] JGJ118—98,冻土地区建筑地基基础设计规范[S].北京:中国建筑工业出版社,1998.
[10] GB50007—2002,建筑地基基础设计规范[S].北京:中国建筑工业出版社,2002.
[11]童长江,管枫年..土的冻胀与建筑物冻害防治[M].北京:水利电力出版社,1985:3—3
[12] Hanley,T.O'D.,Rao,S.R..Electrical freezing potentials and the migration of moisture and ions in freezing soils.“Abstracts”,Fourth Canadian Permafrost Conferegce 1981.
[13]柯洁铭.人工冻土冻胀数值模拟分析[D].南京:南京林业大学,2004.
[14]吴紫汪.土的冻胀性实验研究[G].中国科学院兰州冰川冻土研究所集刊,科学出版,1981.
[15] Johnson,T.C.,Berg,R.L..Roadway design in seasonal frost areas.CRREL Tech.Rept.259.1975.
[16]谢音琦.用压实土做防冻胀地基的探讨[R].抗冻技术情报. 1980,(2).
[17] Wang Mianchang . Frost behaviour of compacted soil . Higway Res.Rec.No.360 .1971.
[18] Takashi,T..Effect of penetration rate of freezing and confining stress on the frost heave ratio of soil.Proc .3rd Int'1.Conf.Permafrost.1978.
[19] Penner , E..Influence of freezing rate on frost heaving.Highway Res.Rec.No.393.1972.
[20] Aitken,G.W..Reduction of frost heave by surcharge stress.CRREL,TR 184.1974.
[21] kaplar,C.W..Freezing test for evaulating relative frost susceptibility of various soil CRREL.TR 250.1974.
[22] Arvidson , W . D ., Morgenstern , N . R .. Water flow induced by soils freezing. Can.Geotech.J.Vol.14,No.2.1977.
[23] Penner,E.and walton,T..Effects of temperature and pressure on frost heaving. Eng.Geol.Vol.13,No.1-4.1979.
[24]吴紫汪,张家懿.冻土融化压力的初步试验[G].青藏冻土研究论文集,北京:科学出版社,1983.
[25] Yong,R.N..Prediction of salt influence on unfrozen water content in frozen soils Engineering Geology Jounal Vol.13,No.1-4.1979
[26]吴紫汪.土冻结时对基础的切向冻胀力实验研究[G].中国科学院兰州冰川冻土研究所集刊,1981.
[27]周长庆.我国冻土地基基础研究成就概述[J].冰川冻土,1980,2(1).
[28]丁靖康.切向冻胀力的野外试验研究[G].第二届全国冻土学术会议论文选集,兰州:甘肃人民出版社,1983.
[29]童长江.基础的冻胀力[G].中国地理学会冰川冻土学术会议论文选集,北京:科学出版社,1982.
[30]吴紫汪.基础与冻土间冻结强度的试验研究[G].中国科学院兰州冰川冻土研究所集刊,北京:科学出版社,1981.
[31]陈肖柏,刘建坤,刘鸿绪.土的冻结作用与地基[M].北京:科学出版社,2006:222
[32]童长江.风火山多年冻土区季节融化层冻结时的法向冻胀力[G].青藏冻土研究论文集,北京:科学出版社,1983.
[33]武汉水利电力学院..水利工程管理[M].北京:水利电力出版社,1990:144—149.
[34]隋咸志.季节冻土区扩大式基础上冻胀反力的计算[J].冰川冻土,1985,7(3):213—220.
[35]中华人民共和国交通部.公路桥梁设计规范[S].北京:人民交通出版社,1995.
[36]赵国逵,苗青.土的冻胀对建筑物的危害与防治[J].低温建筑技术,2001,(3),72—73.
[37]裴章勤,卢继清.国内外物理化学方法防治土体冻胀的研究[J].冰川冻土,1982,4(1).
[38]铁道科学院金化所,天津师范学院化学系.表面活性剂在铁路路基化学防冻胀中的应用研究[G].铁道科学技术公务工程手册,1978.
[39]管枫年.板基法向冻胀力现场试验研究[J].冰川冻土,1981,3(3).
[40]王希尧.水工板式衬砌体的允许冻胀变位和冻胀量估算[J].抗冻技术情报,1983,(2).
[41]周有才.两种刚性基础防冻害效果的对比[G].中国科学院兰州冰川冻土研究所集刊,北京:科学出版社,1990.