Variable Stiffness Leveling Foundation Design and Analysis of CFG Composite Foundation
-
摘要: 北京国际文化硅谷园位于北京朝阳区,工程场区以粉质黏土、粉土与砂土交互沉积为主,且地下水水位较高。该工程纯地下车库区域因自重不满足抗浮要求,采取了抗浮桩措施,同时主楼地基承载力不足,采用了复合地基,形成主楼复合地基+纯地下抗浮桩的型式。需要考虑主楼与纯地下车库,以及主楼的核心筒与外框架柱之间的差异沉降。通过基于地基与结构相互作用的差异沉降变形计算分析,验证控制与协调不均匀沉降的工程措施,设计选择合理的CFG桩持力层,调整主楼CFG桩桩间距、褥垫层厚度而调整地基刚度,并依据差异沉降计算分析优化调整抗浮桩的布置范围,实现了变刚度调平设计。工程检验与沉降实测,验证了本工程地基变刚度调平差异沉降的地基设计方案的合理性。Abstract: Beijing International Culture Silicon Valley Park is located in Chaoyang District, Beijing. The project area is mainly composed of silty clay, silty soil and sandy soil with high groundwater level. In this project the only-underground-building needs anti-floating piles. At the same time, due to large load of the main towers and insufficient foundation bearing capacity, the CFG composite foundation is adopted under the main towers. Thus, CFG composite foundation under the main towers and anti-floating piles under the only-underground-building are used in this project. The differential settlement between towers and only-underground-building and also the core tube and the outer frame column of the tower building is difficult to control. Through the calculation and analysis of differential settlement deformation based on the interaction between geotechnical foundation and structure, the engineering measures for controlling and coordinating differential settlement are verified. The measures include selecting reasonable bearing layer of CFG pile, adjusting the foundation stiffness by using different spacing of CFG piles and cushion thickness, and optimizing the anti-floating piles according to the geotechnical settlement deformation analysis. The variable stiffness between the towers and their skirt buildings as well as the core tube of the tower and the columns of the outer frame is realized. The design is verified by the engineering inspection and settlement measurement.
-
表 1 地层岩性物理力学指标表
地层编号及
岩性天然快剪 压缩模量Es/ MPa 极限侧阻力标准值qsik/kPa 极限端阻力标准值qpk/kPa c /kPa φ/(°) ③细砂–粉砂 (0) (30) 23.00 60 ③1黏质粉土 16 28 55 ③2重粉质黏土 31 15.2 5.37 45 ③3粉砂–细砂 15.0 25.0 15 50 ④粉质黏土 27.86 18.64 7.5 55 ④1砂质粉土 19.85 28.12 12.04 60 ④2粉砂–细砂 0 30 25 60 ④3重粉质黏土 32.17 11.5 5.87 50 ⑤粉质黏土 32 17.81 9.72 60 450 ⑤1黏质粉土 20 29.13 12.68 60 550 ⑤2粉砂–细砂 28.00 65 650 ⑤3重粉质黏土 36 10 6.88 55 400 ⑥粉质黏土 32 21.5 12.58 60 600 ⑥1重粉质黏土 9.1 55 500 ⑥2砂质粉土 65 700 ⑥3粉砂 30 65 750 ⑦细砂–粉砂 (32) 70 1000 ⑦1粉质黏土 11.19 60 650 ⑦2黏质粉土 18.15 65 750 ⑧细砂 (35) 75 1200 ⑧1黏质粉土 (13) 60 800 ⑨粉质黏土 14.3 ⑨1黏质粉土 19.9 ⑨2黏土 13.6 表 2 场地地下水情况一览表
序号 地下水类型 地下水稳定水位
(承压水测压水头)主要含水层 埋深/m 标高/m 1 上层滞水(一) 1.10~3.20 31.02~32.82 2 潜水(二) 4.60~6.60 28.02~29.99 细砂–粉砂③层 3 层间潜水(三)
(具承压性)12.00~18.60 15.70~22.52 粉砂–细砂④2层、粉砂–细砂⑤2层 4 层间潜水(四)
(具承压性)23.10~26.30 7.77~11.55 粉砂⑥3层、细砂–粉砂⑦层 5 承压水(五) 28.50 5.97 细砂⑧层 表 3 CFG桩复合地基设计参数
设计参数 框架柱 主楼其他
区域A01#楼东西侧
及A02#楼南侧其他区域 桩间土承载力
特征值fsk /kPa130 130 130 设计复合地基承载力
标准值fspk /kPa430 620 430 单桩竖向承载力
标准值Rv /kN850 850 850 桩径/mm 400 400 400 有效桩长/m 21.0(桩端持力层:细砂⑧层) 桩身混凝土强度 C30 桩距/m 1.50×1.50 1.20×1.20 1.50×1.50 实际面积置换率/% 5.5 8.7 5.5 -
[1] 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, 2011. [2] 孙宏伟. 岩土工程进展与实践案例汇编 [M]. 北京: 中国建筑工业出版社, 2016. [3] 方云飞, 孙宏伟, 杨 洁, 等. 北京银河搜候(SOHO)中心地基与基础设计分析[J]. 建筑结构,2013,43(17):140-143. [4] JGJ 79—2012 建筑地基处理技术规范 [S]. 北京: 中国建筑工业出版社, 2012. [5] 闫明礼, 张东刚. CFG桩复合地基技术及工程实践 [M]. 北京: 中国水利水电出版社, 2001. [6] 周 宸,化建新,王 健. CFG桩的承载力特性试验研究[J]. 岩土工程技术,2016,(10):217-248. [7] 化建新,闫德刚,赵杰伟,等. 第七届全国岩土工程实录交流会特邀报告−地基处理综述及新进展[J]. 岩土工程技术,2015,(5):285-300. [8] 吴民利. 超薄褥垫层CFG桩复合地基设计与实践[J]. 勘察科学技术,2018,(2):23-27. [9] 郭密文,魏国堂,沈伊晔. 高层建筑大底盘基础下CFG桩复合地基变刚度设计[J]. 工程勘察,2010,(7):22-26. [10] 王 杨,詹永勤. 北京达美中心广场基础变刚度调平设计[J]. 建筑结构,2017,(7):62-66. [11] DBJ 11—501—2009 北京地区建筑地基基础勘察设计规范(2016年版)[S]. 2017. [12] 卢萍珍,于东晖,方云飞,等. CFG桩复合地基增强体偏位影响分析[J]. 建筑结构,2014,(10):126-129. [13] 范崇民,王 超,邴宇峰. CFG桩复合地基的数值模拟分析[J]. 岩土工程技术,2013,(3):13-16. [14] 周 宸,李宝强,王 健. CFG桩复合地基沉降三维数值模拟研究[J]. 岩土工程技术,2015,(6):118-121.