深大沉井下沉阻力的现场监测
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摘要
分析刃脚土阻力与侧壁摩阻力的大小和变化规律是沉井设计计算的重要内容,现有规范中所给的计算方法是否适用于大型沉井基础的设计计算,还需进一步验证。为此,通过布置刃脚踏面土压力传感器、侧壁土压力传感器以及GPS沉井姿态监测系统,对沪通长江大桥主墩沉井的下沉阻力开展了现场监测。结合大量现场监测资料,分析了大型沉井基础下沉期间的下沉机理与下沉阻力分布特征,对目前沉井下沉阻力计算中常用的规范和计算方法的适用性进行了分析,结果表明:目前的设计计算方法在计算刃脚土阻力时均未考虑刃脚所在土层前期固结压力的影响,因此,此类计算方法仅适用于沉井入土深度较小、刃脚所在土层前期固结压力不大的情况,当沉井入土深度较大时,计算值与实际值相比明显偏小;由于压力松弛效应,沉井侧壁摩阻力随入土深度的增大呈先增大后减小的变化规律,压力松弛区影响高度≥5 m。另根据现场监测结果,提出了侧壁摩阻力分布简化模型,分为以下3个阶段:第1阶段为线性增加阶段,侧壁摩阻力分布模式为三角形分布;第2阶段为压力松弛影响阶段,侧壁摩阻力分布模式为三角形分布+倒三角形分布;第3阶段为压力松弛下移阶段,摩阻力分布模式为梯形分布。研究结果可为沉井设计计算方法的优化提供参考。
The analysis of the size and change rules of resistance on blade foot soil friction resistance on side wall is an important part of the design and calculation of caisson. Whether the calculation method in the current specification is applicable to the design calculation of large caisson needs further verification. For this reason, the field monitoring of the sinking resistance of the main pier caisson of Hutong Changjiang River Bridge is conducted by arranging earth pressure sensor of blade foot tread, side wall earth pressure sensor and GPS caisson attitude monitoring system. Combining with a large number of field monitoring data, the sinking mechanism and the distribution of the sinking resistance of large caisson foundation during the period of sinking are analyzed, and the applicability of the specifications and calculation methods commonly used in the calculation of sinking resistance is analyzed. The result shows that(1) The current design and calculation method does not consider the effect of the pre-consolidation pressure on the soil layer where the blade foot is located, so these methods are only applicable to the condition of the smaller depth of the caisson and the smaller pressure of the pre-consolidation of the said soil layer. When the depth of the caisson is larger, the calculated value is obviously smaller than the actual value.(2) Because of pressure relaxation effect, the frictional resistance on side wall of the caisson increases at first and then decreases with the increase of the depth, and the height of the pressure relaxation zone is more than 5 m. Also, a simplified model of the distribution of friction resistance is presented according to the measured result. It can be divided into 3 stages: the first stage is the linear increase stage, the distribution pattern of side wall frictional resistance is triangular distribution; the second stage is the pressure relaxation influence stage, the distribution pattern of side wall frictional resistance is triangular+inverted triangular distribution; the third stage is the pressure relaxation downward phase, the distribution pattern of side wall frictional resistance is trapezoidal distribution. The research result can provide a reference for the optimization of caisson design calculation method.
The analysis of the size and change rules of resistance on blade foot soil friction resistance on side wall is an important part of the design and calculation of caisson. Whether the calculation method in the current specification is applicable to the design calculation of large caisson needs further verification. For this reason, the field monitoring of the sinking resistance of the main pier caisson of Hutong Changjiang River Bridge is conducted by arranging earth pressure sensor of blade foot tread, side wall earth pressure sensor and GPS caisson attitude monitoring system. Combining with a large number of field monitoring data, the sinking mechanism and the distribution of the sinking resistance of large caisson foundation during the period of sinking are analyzed, and the applicability of the specifications and calculation methods commonly used in the calculation of sinking resistance is analyzed. The result shows that(1) The current design and calculation method does not consider the effect of the pre-consolidation pressure on the soil layer where the blade foot is located, so these methods are only applicable to the condition of the smaller depth of the caisson and the smaller pressure of the pre-consolidation of the said soil layer. When the depth of the caisson is larger, the calculated value is obviously smaller than the actual value.(2) Because of pressure relaxation effect, the frictional resistance on side wall of the caisson increases at first and then decreases with the increase of the depth, and the height of the pressure relaxation zone is more than 5 m. Also, a simplified model of the distribution of friction resistance is presented according to the measured result. It can be divided into 3 stages: the first stage is the linear increase stage, the distribution pattern of side wall frictional resistance is triangular distribution; the second stage is the pressure relaxation influence stage, the distribution pattern of side wall frictional resistance is triangular+inverted triangular distribution; the third stage is the pressure relaxation downward phase, the distribution pattern of side wall frictional resistance is trapezoidal distribution. The research result can provide a reference for the optimization of caisson design calculation method.
引文
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[15]孟颂颂.不同前期固结压力下粉砂类滑带土抗剪强度环剪试验研究[C]//2016年全国工程地质学术年会论文集.北京:中国地质学会工程地质专业委员会,2016:1355-1361.MENG Song-song.Shear Strength Behavior of Silty Sand Type Landslide Soil under Different pre-consolidation Pressures in Ring Shear Tests[C]//Proceedings of the National Engineering Geology Conference.Beijing:Engineering Geology Professional Committee of China Geological Society,2016:1355-1361.
[16]大桥局桥梁研究所.沉井下沉时土阻力的测量[J].桥梁建设,1974(3):33-43.Bridge Research Institute of Bridge Bureau.Measurement of Soil Resistance in Settlement of Sinking Wells[J].Bridge Construction,1974(3):33-43.
[17]李宗哲,朱婧,居炎飞,等.大型沉井群的沉井下沉阻力监测技术[J].华中科技大学学报:城市科学版,2009,26(2):43-46,51.LI Zong-zhe,ZHU Jing,JU Yan-fei,et al.Monitoring Technique for Sinking Resistance of Large Caisson Group[J].Journal of Huazhong University of Science and Technology:Urban Science Edition,2009,26(2):43-46,51.
[18]陈晓平,茜平一,张志勇.沉井基础下沉阻力分布特征研究[J].岩土工程学报,2005,27(2):148-152.CHEN Xiao-ping,QIAN Ping-yi,ZHANG Zhi-yong.Study on Penetration Resistance Distribution Characteristic of Sunk Shaft Foundation[J].Chinese Journal of Geotechnical Engineering,2005,27(2):148-152.
[2]吉林,阮静,王陶.泰州大桥三塔两跨悬索桥关键技术[J].公路交通科技,2015,32(2):94-99.JI Lin,RUAN Jing,WANG Tao.Key Technology of 3-pylon 2-span Suspension Bridge of Taizhou Bridge[J].Journal of Highway and Transportation Research and Development,2015,32(2):94-99.
[3]穆保岗,朱建民,龚维明,等.悬索桥大型沉井排水下沉控制的关键问题分析[J].中国公路学报,2013,26(6):118-127.MU Bao-gang,ZHU Jian-min,GONG Wei-ming,et al.Key Issues about Drainage Sinking Control of Large Caissons in Suspension Bridge[J].China Journal of Highway and Transport,2013,26(6):118-127.
[4]郑大超,朱斌.武汉杨泗港长江大桥2号墩钢沉井施工关键技术[J].桥梁建设,2017,47(6):106-110.ZHENG Da-chao,ZHU Bin.Key Techniques for Construction of Steel Open Caisson of Pier No.2 of Yangsigang Changjiang River Bridge in Wuhan[J].Bridge Construction,2017,47(6):106-110.
[5]CECS 137-2015,给水排水工程钢筋混凝土沉井结构设计规程[S].CECS 137-2015,Specification for Structural Design of Reinforced Concrete Sinking Well of Water Supply and Sewerage Engineering[S].
[6]TB 10002.5-2005,铁路桥涵地基和基础设计规范[S].TB 10002.5-2005,Code for Design on Subsoil and Foundation of Railway Bridge and Culvert[S].
[7]JTG D63-2007,公路桥涵地基与基础设计规范[S].JTG D63-2007,Code for Design of Ground Base and Foundation of Highway Bridges and Culverts[S].
[8]GB 50007-2011,建筑地基基础设计规范[S].GB 50007-2011,Code for Design of Building Foundation[S].
[9]郑大同.地基极限承载力的计算[M].北京:中国建筑工业出版社,1979.ZHENG Da-tong.Calculation of Ultimate Bearing Capacity of Foundation[M].Beijing:China Architecture&Building Press,1979.
[10]穆保岗,朱建民,龚维明.大型沉井设计、施工及监测[M].北京:中国建筑工业出版社,2015.MU Bao-gang,ZHU Jian-min,GONG Wei-ming.Design,Construction and Monitoring of Large Caisson[M].Beijing:China Architecture&Building Press,2015.
[11]徐力,高宗余,梅新咏.沪通长江大桥公铁合建斜拉桥桥塔基础设计[J].桥梁建设,2015,45(3):7-12.XU Li,GAO Zong-yu,MEI Xin-yong.Design of Pylon Foundations for Rail-cum-road Cable-stayed Bridge of Hutong Changjiang River Bridge[J].Bridge Construction,2015,45(3):7-12.
[12]高宗余,梅新咏,徐伟,等.沪通长江大桥总体设计[J].桥梁建设,2015,45(6):1-6.GAO Zong-yu,MEI Xin-yong,XU Wei,et al.Overall Design of Hutong Changjiang River Bridge[J].Bridge Construction,2015,45(6):1-6.
[13]李军堂.沪通长江大桥主航道桥沉井施工关键技术[J].桥梁建设,2015,45(6):12-17.LI Jun-tang.Key Techniques for Construction of Open Caissons of Main Ship Channel Bridge of Hutong Changjiang River Bridge[J].Bridge Construction,2015,45(6):12-17.
[14]胡伟明,马建林,李军堂,等.超大截面沉井着床行为判别分析[J].桥梁建设,2016,46(2):115-120.HU Wei-ming,MA Jian-lin,LI Jun-tang,et al.Judgment Analysis of Behavior of Landing Super Large Section Caisson onto Riverbed[J].Bridge Construction,2016,46(2):115-120.
[15]孟颂颂.不同前期固结压力下粉砂类滑带土抗剪强度环剪试验研究[C]//2016年全国工程地质学术年会论文集.北京:中国地质学会工程地质专业委员会,2016:1355-1361.MENG Song-song.Shear Strength Behavior of Silty Sand Type Landslide Soil under Different pre-consolidation Pressures in Ring Shear Tests[C]//Proceedings of the National Engineering Geology Conference.Beijing:Engineering Geology Professional Committee of China Geological Society,2016:1355-1361.
[16]大桥局桥梁研究所.沉井下沉时土阻力的测量[J].桥梁建设,1974(3):33-43.Bridge Research Institute of Bridge Bureau.Measurement of Soil Resistance in Settlement of Sinking Wells[J].Bridge Construction,1974(3):33-43.
[17]李宗哲,朱婧,居炎飞,等.大型沉井群的沉井下沉阻力监测技术[J].华中科技大学学报:城市科学版,2009,26(2):43-46,51.LI Zong-zhe,ZHU Jing,JU Yan-fei,et al.Monitoring Technique for Sinking Resistance of Large Caisson Group[J].Journal of Huazhong University of Science and Technology:Urban Science Edition,2009,26(2):43-46,51.
[18]陈晓平,茜平一,张志勇.沉井基础下沉阻力分布特征研究[J].岩土工程学报,2005,27(2):148-152.CHEN Xiao-ping,QIAN Ping-yi,ZHANG Zhi-yong.Study on Penetration Resistance Distribution Characteristic of Sunk Shaft Foundation[J].Chinese Journal of Geotechnical Engineering,2005,27(2):148-152.