Field measurement and mechanism of inclined and vertical piles in foundation pits
-
摘要: 斜直交替基坑支护结构是利用冠梁将交替布置的竖直悬臂桩与倾斜桩连接到一起形成的无支撑支护体系。已有工程实测表明，斜直交替支护具有较好的抗倾覆和变形控制能力，然而目前还缺乏从桩身受力角度对斜直交替支护受力机理进行系统研究。结合天津市某基坑工程进行斜直交替支护桩现场监测，首次对支护斜桩的桩身受力进行测试和分析，在此基础上利用PLAXIS有限元软件进行数值建模，对斜桩轴力发挥机理以及斜桩倾斜角度、斜直桩排布形式对支护性能的影响展开研究。结果表明，斜直交替支护比单排倾斜桩和双排桩支护桩的桩身轴力更大，斜桩对直桩存在着斜撑效应，且斜撑效应对支护结构变形的控制效果明显，斜撑效应的发挥主要来源于斜桩与被动区土体相对位移产生桩侧摩阻力；同时发现增大斜桩倾斜角度有利于增强斜桩的斜撑效应，使得支护桩侧移减小，但同时支护桩的桩身最大正弯矩会增加；此外，在用桩量相同的情况下，不同斜直桩组合及布置形式对支护变形影响较小，采用一斜两直的布置形式，能够在降低施工难度的同时减少直桩的受力。Abstract: The inclined and vertical support for foundation pits is a kind of unsupported support system, which is formed by using the crown beam to connect the vertical cantilever pile and the inclined pile. The measured results of the existing projects show that the inclined and vertical alternate support has better anti-overturning and deformation control capability. However, there is still a lack of systematic research on the mechanism of inclined and vertical alternate support from the perspective of pile stress. Based on the field tests on the inclined and vertical alternate support piles in a foundation pit project in Tianjin, the forces of the inclined pile are monitored and analyzed. On this basis, the numerical modeling is carried out by using the finite element software PLAXIS. The mechanism of the axial forces of the inclined pile and the influences of the inclined angle and the arrangement of the inclined and vertical piles on the supporting performance are studied. The results show that the axial forces of the pile shaft are greater than those of the single-row inclined piles and double-row support piles, and the effect of inclined support is obvious to the deformation control of the support structures. The effect of inclined support is mainly due to the relative displacement of the inclined pile and the soil in the passive area to produce the side friction resistance of the pile. At the same time, it is found that increasing the inclined angle of the inclined pile is conducive to the inclined support of the inclined pile, which makes the lateral displacement of the support pile decrease, but the maximum positive bending moment of the pile shaft will increase at the same time. In addition, under the same amount of piles, different arrangements of inclined and vertical piles have small influences on the deformation of the support. The arrangement of one inclined and two vertical piles can reduce the stress of the vertical pile and the construction difficulty.
-
-
![]()
图 5 桩顶水平位移随开挖的变化曲线
Figure 5. Variation curves of horizontal displacement at pile top with excavation
![]()
图 10 斜直交替支护作用机理示意图
Figure 10. Schematic diagram of action mechanism of inclined and vertical alternate support
![]()
图 12 不同支护形式的桩身侧移和弯矩曲线
Figure 12. Curves of lateral displacement and bending moment of piles with different support forms
![]()
图 13 不同支护形式的桩身轴力曲线
Figure 13. Curves of axial force of piles with different support forms
![]()
图 14 不同支护形式的坑内土体隆起
Figure 14. Soil uplift in fondation pit with different support forms
![]()
图 15 不同斜桩最大侧摩阻力的直桩桩身侧移图
Figure 15. Horizontal displacements of piles with different maximum side frictions
![]()
图 16 不同最大侧摩阻力的斜桩桩身轴力与侧阻力
Figure 16. Axial forces and lateral resistances of inclined pile with different maximum lateral frictions
![]()
图 17 斜桩与桩周土体的竖向位移
Figure 17. Vertical displacements of inclined pile and soil around pile
![]()
图 18 斜直交替支护的土体竖向位移云图
Figure 18. Nephogram of vertical displacement of soil mass with inclined and vertical alternate support
![]()
图 19 斜直交替支护的土体总位移矢量图
Figure 19. Vector diagram of total displacement of soil mass with inclined and vertical alternate support
![]()
图 20 不同斜桩倾角时的直桩桩身水平位移图
Figure 20. Horizontal displacements of vertical pile with different inclined angles
表 1 试验场地土层物理力学参数
Table 1 Physical and mechanical parameters of soil layers in test site
土层 层厚
/m含水率
w /%重度
/(kN·m-3)孔隙比
e压缩模量
Es1-2/MPa直剪固结快剪 黏聚力ccu/kPa 内摩擦角φcu/(°) ①2素填土 2.4 30.59 18.6 0.94 3.59 20.51 11.72 ③1黏土 1.7 32.87 18.7 0.96 3.91 16.47 12.69 ⑥1淤泥质粉质黏土 5.8 36.17 18.5 1.03 3.68 14.80 12.94 ⑥2粉质黏土 5.0 29.80 19.2 0.84 4.93 16.99 18.62 ⑥3粉土 0.8 24.74 19.9 0.70 11.73 7.87 31.12 ⑦粉质黏土 2.3 23.43 20.1 0.66 5.44 18.82 17.21 ⑧1粉质黏土 1.5 23.19 20.2 0.67 5.52 22.68 14.16 ⑧2粉砂 3.2 17.26 20.9 0.52 13.68 5.15 35.47 ⑨1粉质黏土 4.0 23.82 20.1 0.68 5.56 21.22 16.41 ⑨2粉砂 5.2 21.67 20.3 0.62 13.27 5.84 32.83 ⑪2粉砂 8.4 21.55 20.2 0.63 14.30 5.64 33.79 
下载: 导出CSV
表 2 土体材料计算参数
Table 2 Parameters of soil materials
土层名称 厚度/m 重度/(kN·m-3) ccu/kPa φcu/(°) E50/MPa Eoed/MPa Eur/MPa G0 ref/MPa ①2素填土 2.4 18.6 20.51 11.72 3.8 3.8 26.6 106.4 ③1黏土 1.7 18.7 16.47 12.69 4.1 4.1 28.7 114.8 ⑥1淤泥质粉质黏土 5.8 18.5 14.80 12.94 3.8 3.8 30.4 121.6 ⑥2粉质黏土 5.0 19.2 16.99 18.62 5.1 5.1 35.7 142.8 ⑥3粉土 0.8 19.9 7.87 31.12 12.5 12.5 62.5 187.5 ⑦粉质黏土 2.3 20.1 18.82 17.21 5.6 5.6 39.2 156.8 ⑧1粉质黏土 1.5 20.2 22.68 14.16 5.7 5.7 39.9 159.6 ⑧2粉砂 3.2 20.9 5.15 35.47 14.5 14.5 72.5 217.5 ⑨1粉质黏土 4.0 20.1 21.22 16.41 5.7 5.7 39.9 159.6 ⑨2粉砂 5.2 20.3 5.84 32.83 13.9 13.9 69.5 208.5 ⑪2粉砂 13.0 20.2 5.64 33.79 14.8 14.8 74.0 222.0
下载: 导出CSV
表 3 不同斜桩倾角的支护桩桩身最大轴力与弯矩
Table 3 Maximum axial forces and bending moments of support piles with different inclined angles
斜桩倾角/(°) 桩身最大正弯矩/(kN·m) 桩身最大负弯矩/(kN·m) 斜桩最大轴力/kN 直桩最大轴力/kN 斜桩 直桩 斜桩 直桩 5 70.4 8.1 -169.3 -164.4 -87.5 73.5 10 116.8 34.4 -117.7 -109.8 -112.9 95.6 15 134.3 74.3 -71.5 -80.7 -151.8 112.0 20 130.0 90.9 -54.2 -62.1 -203.7 133.1 25 92.1 115.6 -40.0 -40.6 -224.1 143.0 30 63.4 150.3 -21.4 -18.7 -235.3 151.1
下载: 导出CSV
表 4 不同斜直桩排布形式的桩身受力与变形
Table 4 Stresses and deformations of piles with different arrangements of inclined and vertical piles
斜直桩排布方式 直桩弯矩/(kN·m) 每延米的斜桩轴力/(kN·m-1) 直桩最大水平位移/mm 最大负
弯矩最大正弯矩 一斜两直 -112.7 125.2 -113.731 27.6 一斜一直 -93.1 136.3 -143.667 24.1 两斜一直 -104.9 149.8 -171.154 23.2 三斜一直 -125.5 171.3 -190.179 25.9
下载: 导出CSV
-
[1] 郑刚, 朱合华, 刘新荣, 等. 基坑工程与地下工程安全及环境影响控制[J]. 土木工程学报, 2016, 49(6): 1–24. https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC201606001.htm ZHENG Gang, ZHU He-hua, LIU Xin-rong, et al. Control of safety of deep excavations and underground engineering and its impact on surrounding environment[J]. China Civil Engineering Journal, 2016, 49(6): 1–24. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC201606001.htm
[2] 陈昆, 闫澍旺, 张智, 等. 不同内支撑支护体系对深基坑开挖变形的影响分析[J]. 天津大学学报(自然科学与工程技术版), 2017, 50(增刊1): 1–6. https://www.cnki.com.cn/Article/CJFDTOTAL-TJDX2017S1001.htm CHEN Kun, YAN Shu-wang, ZHANG Zhi, et al. Impact analysis of deep foundation pit excavation under different bracing system[J]. Journal of Tianjin University (Science and Technology), 2017, 50(S1): 1–6. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-TJDX2017S1001.htm
[3] 郭建芝, 曹华先. 斜桩挡土支护深基坑[J]. 广州建筑, 1997, 25(2): 38–41. https://www.cnki.com.cn/Article/CJFDTOTAL-GZJZ199702007.htm GUO Jian-zhi, CAO Hua-xian. Batter pile strutted deep foundation pit[J]. Guangzhou Architecture, 1997, 25(2): 38–41. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-GZJZ199702007.htm
[4] MAEDA T, SHIMADA Y, TAKAHASHI S, et al. Design and construction of inclined-braceless excavation support applicable to deep excavation[C]// International Conference on Soil Mechanics and Geotechnical Engineering, 2013, Paris.
[5] 孔德森, 张秋华, 史明臣. 基坑悬臂式倾斜支护桩受力特性数值分析[J]. 地下空间与工程学报, 2012, 8(4): 742–747. https://www.cnki.com.cn/Article/CJFDTOTAL-BASE201204013.htm KONG De-sen, ZHANG Qiu-hua, SHI Ming-chen. Study on the bearing behavior charactersitcis of cantilever inclined retaining pile for foundation pit[J]. Chinese Journal of Underground Space and Engineering, 2012, 8(4): 742–747. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-BASE201204013.htm
[6] 孔德森, 张秋华, 史明臣. 基坑倾斜支护桩模型试验的数值模拟研究[J]. 岩土工程学报, 2011, 33(增刊2): 408–411. http://manu31.magtech.com.cn/Jwk_ytgcxb/CN/abstract/abstract14390.shtml KONG De-sen, ZHANG Qiu-hua, SHI Ming-chen. Numerical simulation of model tests on inclined retaining piles in foundation pit[J]. Chinese Journal of Geotechnical Engineering, 2011, 33(S2): 408–411. (in Chinese) http://manu31.magtech.com.cn/Jwk_ytgcxb/CN/abstract/abstract14390.shtml
[7] 孔德森, 张杰, 王士权, 等. 基坑支护倾斜悬臂桩受力变形特性试验研究[J]. 地下空间与工程学报, 2020, 16(1): 160–168. https://www.cnki.com.cn/Article/CJFDTOTAL-BASE202001021.htm KONG De-sen, ZHANG Jie, WANG Shi-quan, et al. Experimental study on stress and deformation characteristics of cantilever inclined retaining pile for foundation pit support[J]. Chinese Journal of Underground Space and Engineering, 2020, 16(1): 160–168. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-BASE202001021.htm
[8] SEO M, IM J C, KIM C, et al. Study on the applicability of a retaining wall using batter piles in clay[J]. Canadian Geotechnical Journal, 2016, 53(8): 1195–1212. doi: 10.1139/cgj-2014-0264
[9] 郑刚, 白若虚. 倾斜单排桩在水平荷载作用下的性状研究[J]. 岩土工程学报, 2010, 32(增刊1): 39–45. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC2010S1009.htm ZHENG Gang, BAI Ruo-xu. Behaviors study of inclined single row contiguous retaining piles under horizontal force[J]. Chinese Journal of Geotechnical Engineering, 2010, 32(S1): 39–45. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC2010S1009.htm
[10] 刁钰, 苏奕铭, 郑刚. 主动式斜直交替倾斜桩支护基坑数值研究[J]. 岩土工程学报, 2019, 41(增刊1): 161–164. http://manu31.magtech.com.cn/Jwk_ytgcxb/CN/abstract/abstract17936.shtml DIAO Yu, SU Yi-ming, ZHENG Gang. Numerical study on oblique-straight alternate piles for active support of excavations[J]. Chinese Journal of Geotechnical Engineering, 2019, 41(S1): 161–164. (in Chinese) http://manu31.magtech.com.cn/Jwk_ytgcxb/CN/abstract/abstract17936.shtml
[11] 王恩钰, 周海祚, 郑刚, 等. 基坑倾斜桩支护的变形数值分析[J]. 岩土工程学报, 2019, 41(增刊1): 73–76. http://manu31.magtech.com.cn/Jwk_ytgcxb/CN/abstract/abstract17914.shtml WANG En-yu, ZHOU Hai-zuo, ZHENG Gang, et al. Numerical analyses of deformation of inclined pile-retained excavations[J]. Chinese Journal of Geotechnical Engineering, 2019, 41(S1): 73–76. (in Chinese) http://manu31.magtech.com.cn/Jwk_ytgcxb/CN/abstract/abstract17914.shtml
[12] 刘涛. 倾斜桩在基坑支护中的作用机理和简化计算方法[D]. 天津: 天津大学, 2018. LIU Tao. The Function Mechanism and Simplified Calculation Method of Inclined Pile in Foundation Pit Support[D]. Tianjin: Tianjin University, 2018. (in Chinese).
[13] 张秋华. 基坑支护倾斜桩的受力变形特性及其影响因素分析[D]. 青岛: 山东科技大学, 2012. ZHANG Qiu-hua. Analysis of Deformation Char-Acteristics and Influencing Factors of Inclined Pile in Foundation Pit Support[D]. Qingdao: Shandong University of Science and Technology, 2012. (in Chinese).
[14] OU C Y, HSIEH P G, CHIOU D C. Characteristics of ground surface settlement during excavation[J]. Canadian Geotechnical Journal, 1993, 30(5): 758–767.
[15] JARDINE R J, POTTS D M, FOURIE A B, et al. Studies of the influence of non-linear stress–strain characteristics in soil–structure interaction[J]. Géotechnique, 1986, 36(3): 377–396.
[16] 尹骥. 小应变硬化土模型在上海地区深基坑工程中的应用[J]. 岩土工程学报, 2010, 32(增刊1): 166–172. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC2010S1033.htm YIN Ji. Application of hardening soil model with small strain stiffness in deep foundation pits in Shanghai[J]. Chinese Journal of Geotechnical Engineering, 2010, 32(S1): 166–172. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC2010S1033.htm
[17] 郑刚, 何晓佩, 周海祚, 等. 基坑斜–直交替支护桩工作机理分析[J]. 岩土工程学报, 2019, 41(增刊1): 97–100. http://manu31.magtech.com.cn/Jwk_ytgcxb/CN/abstract/abstract17920.shtml ZHENG Gang, HE Xiao-pei, ZHOU Hai-zuo, et al. Working mechanism of inclined-vertical retaining piles in excavations[J]. Chinese Journal of Geotechnical Engineering, 2019, 41(S1): 97–100. (in Chinese) http://manu31.magtech.com.cn/Jwk_ytgcxb/CN/abstract/abstract17920.shtml
[18] 徐源, 郑刚, 路平. 前排桩倾斜的双排桩在水平荷载下的性状研究[J]. 岩土工程学报, 2010, 32(增刊1): 93–98. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC2010S1019.htm XU Yuan, ZHENG Gang, LU Ping. Behaviors of double-row contiguous retaining piles with raking front-row piles under horizontal loads[J]. Chinese Journal of Geotechnical Engineering, 2010, 32(S1): 93–98. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC2010S1019.htm
计量
- 文章访问数: 262
- HTML全文浏览量: 33
- PDF下载量: 174
