膨胀土地基桩基承载特性模型试验研究
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摘要
输电杆塔基础的修建往往需要穿越复杂地质条件地区,膨胀土地基在遇水失水过程中剧烈的膨胀性和收缩性,不仅会引起土体强度改变,同时会引发膨胀变形,二者耦合作用使得膨胀土地基承载力的变化更为复杂。对此开展大尺寸模型试验,通过改变土体含水率,研究膨胀土地基中桩基在最优含水率和饱和含水率条件下的抗压承载力和抗拔承载力变化。研究表明:膨胀土含水率的变化,对抗压过程中的极限承载力影响更为明显,对抗拔过程中的极限位移影响更为明显。随着含水率的增加,桩身极限侧摩阻力和桩端阻力均在减小,但极限端阻力减小幅度大于极限侧摩阻力。同一含水率情况下,抗压试验桩身极限侧摩阻力呈抛物线形分布,而抗拔试验桩身极限侧摩阻力呈线性分布。
The construction of transmission tower foundation often needs to pass through the area of complex geological conditions.The swelling and shrinkage of expansive soil foundation in the process of water loss will not only cause the change of soil strength,but also cause expansion deformation.The interaction between them makes the change of the bearing capacity of expansive soil foundation more complicated.In this paper,a large-scale model test is carried out to study the change of compressive and pull-out bearing capacity of pile foundation in the condition of optimal moisture content and saturated water content.The results show that with the change of moisture content of expansive soil,the influence of ultimate compressive bearing capacity is more obvious and the influence of pull-out ultimate displacement is more obvious.With the increase of water content,both the ultimate side friction and end resistance decrease,but the limit end resistance decreases more than the limit side friction.Under the condition of the same moisture content,the lateral friction distribution of the compressive test pile is parabola,while that of the pull-out test pile is linear.
The construction of transmission tower foundation often needs to pass through the area of complex geological conditions.The swelling and shrinkage of expansive soil foundation in the process of water loss will not only cause the change of soil strength,but also cause expansion deformation.The interaction between them makes the change of the bearing capacity of expansive soil foundation more complicated.In this paper,a large-scale model test is carried out to study the change of compressive and pull-out bearing capacity of pile foundation in the condition of optimal moisture content and saturated water content.The results show that with the change of moisture content of expansive soil,the influence of ultimate compressive bearing capacity is more obvious and the influence of pull-out ultimate displacement is more obvious.With the increase of water content,both the ultimate side friction and end resistance decrease,but the limit end resistance decreases more than the limit side friction.Under the condition of the same moisture content,the lateral friction distribution of the compressive test pile is parabola,while that of the pull-out test pile is linear.
引文
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[13] 潘晨晨,杨敏,上官士青,等.物理模型试验中桩或梁的材料特性及选取依据[J].结构工程师,2018,34(4):135-141.Pan Chenchen,Yang Min,Shangguan Shiqing,et al.Material characteristics of piles and beams in physical model tests and the basis of selecting materials[J].Structural Engineers,2018,34(4):135-141.(in Chinese)
[14] 王杰,梁发云,李元齐,等.基础宽高比对扩展基础基底压力分布影响规律数值模拟[J].结构工程师,2017,33(6):162-168.Wang Jie,Liang Fayun,Li Yuanqi,et al.Numerical simulation about influence of foundation’s width-to-height ratio on contact pressure distribution of spread foundation[J].Structural Engineers,2017,33(6):162-168.(in Chinese)
[15] Liu Y,Vanapalli S K.Influence of lateral swelling pressure on the geotechnical infrastructure in expansive soils[J].Journal of Geotechnical and Geoenvironmental Engineering,2017,143(6):04017006.
[16] 陈铁林,陈生水,顾行文,等.折减吸力在膨胀土静止土压力计算中的应用[J].岩土工程学报,2008,30(2):237-242.Chen Tielin,Chen Shengshui,Gu Xingwen,et al.Applicationof reduced suction in calculation of soil earth pressure at rest for expansive soils[J].Chinese Journal of Geotechnical Engineering,2008,30(2):237-242.(in Chinese)
[2] 孙长龙,殷宗泽,王福升.膨胀土性质研究综述[J].水利水电新科技进展,1995,15(6):10-14.Sun Changlong,Yin Zongze,Wang Fusheng.Review on the properties of expansive soil[J].Advances in Scienceand Technology of Water Resources,1995,15(6):10-14.(in Chinese)
[3] Mohamedzein Y E A,Mohamed M G,Sharief A M E.Finite element analysis of short piles in expansive soils[J].Computers and Geotechnics,1999,24(3):231-243.
[4] 邓长茂,李镜培.合肥膨胀土基坑工程事故分析与预防[J].结构工程师,2011,27(1):105-109.Deng Changmao,Li Jingpei.Analysis and prevention of foundation pit accidents in Hefei district[J].Structural Engineers,2011,27(1):105-109.(in Chinese)
[5] 刘克文,阮永芬,贾荣谷,等.膨胀土场地基坑支护设计施工措施[J].结构工程师,2017,33(3):193-198.Liu Kewen,Ruan Yongfen,Jia Ronggu,et al.Construction & design measures of foundation pit supportingon expansive soil site[J].Structural Engineers,2017,33(3):193-198.(in Chinese)
[6] Collins L E.A preliminary theory for the design of underreamed piles[J].Civil Engineering,1953,3-11.
[7] Prakash,Chandra.Performance of instrumentedunderreamed pile foundation supporting a single storey structure in expansive soil[J].Indian Geotechnical Journal,1988,18(4):340-355.
[8] Sorochan E A.Use of piles in expansive soils[J].Soil Mechanics and Foundation Engineering,1974,11(1):33-38.
[9] 徐永福.膨胀土地基承载力研究[J].岩石力学与工程学报,2000,19(3):387-390.Xu Yongfu.Study on bearing capacity of expansive soil basement[J].Chinese Journal of Rock Mechanics and Engineering,2000,19(3):387-390.(in Chinese)
[10] 陈忠伟.膨胀土中群桩的工作特性[J].建筑科学,2000,16(2):27-30.Chen Zhongwei.Working characteristics of pile groups in expansive soil[J].Building Science,2000,16(2):27-30.(in Chinese)
[11] 杨晶,白晓红,贺武斌,等.具有浸水轻微膨胀性质的压实粉土承载比试验研究[J].结构工程师,2014,30(2):121-126.Yang Jing,Bai Xiaohong,He Wubin,et al.Study on the CBR test of compacted siltwith slight swelling properties[J].Structural Engineers,2014,30(2):121-126.(in Chinese)
[12] 高忠,熊仲明.膨胀土中桩的胀切力计算研究[J].西安建筑利技大学学报(自然科学版),2003,35(4):412-415.Gao Zhong,Xiong Zhongming.Study on the swelling shear of the calculation of piles in swelling soil[J].Journal of Xian University of Architecture & Technology (Natural Science Edition),2003,35(4):412-415.(in Chinese)
[13] 潘晨晨,杨敏,上官士青,等.物理模型试验中桩或梁的材料特性及选取依据[J].结构工程师,2018,34(4):135-141.Pan Chenchen,Yang Min,Shangguan Shiqing,et al.Material characteristics of piles and beams in physical model tests and the basis of selecting materials[J].Structural Engineers,2018,34(4):135-141.(in Chinese)
[14] 王杰,梁发云,李元齐,等.基础宽高比对扩展基础基底压力分布影响规律数值模拟[J].结构工程师,2017,33(6):162-168.Wang Jie,Liang Fayun,Li Yuanqi,et al.Numerical simulation about influence of foundation’s width-to-height ratio on contact pressure distribution of spread foundation[J].Structural Engineers,2017,33(6):162-168.(in Chinese)
[15] Liu Y,Vanapalli S K.Influence of lateral swelling pressure on the geotechnical infrastructure in expansive soils[J].Journal of Geotechnical and Geoenvironmental Engineering,2017,143(6):04017006.
[16] 陈铁林,陈生水,顾行文,等.折减吸力在膨胀土静止土压力计算中的应用[J].岩土工程学报,2008,30(2):237-242.Chen Tielin,Chen Shengshui,Gu Xingwen,et al.Applicationof reduced suction in calculation of soil earth pressure at rest for expansive soils[J].Chinese Journal of Geotechnical Engineering,2008,30(2):237-242.(in Chinese)