-
摘要: 为揭示水泥粉煤灰后压浆对湿陷性黄土桩网结构路基的加固机理，开展后压浆水泥粉煤灰碎石桩室内静载试验，分析了后压浆对桩周土样湿陷系数的影响，研究了竖向静载作用下后压浆桩网结构路基沿深度方向附加应力、桩侧摩阻力及桩端阻力的变化规律；基于Boltzmann数学模型和荷载传递函数，分析了桩侧摩阻力和桩端阻力增强机理，给出后压浆桩侧摩阻力和桩端阻力计算式；利用数值模拟方法，探讨了桩体弹性模量、后压浆深度、桩网置换率和褥垫层厚度对桩网结构路基承载力的影响机制。研究结果表明：在相同荷载作用下，经水泥粉煤灰后压浆处理后的桩周土体的湿陷系数小于自然土样的湿陷系数，且小于0.015；压浆后，静载作用下桩网结构路基中桩顶的竖向附加应力逐渐减小，桩间土的竖向附加应力先减小后增大，桩侧摩阻力较未压浆桩增大了约1.54倍；随着注浆深度的增加，桩身深度方向上的应力最大值呈先增大后减小趋势，且在等桩长深度处取得应力最大值；当桩网置换率提高1倍时，沿深度方向的应力和沉降均减小，其中应力峰值降低24%，沉降量减小26%；桩网结构路基中随着褥垫层厚度的增大，路基深度方向上应力逐渐增大。可见，水泥粉煤灰处理湿陷性黄土路基能减弱路基土体湿陷性，提高承载力，在施工过程中需要考虑桩体弹性模量、后压浆深度、桩网置换率和褥垫层厚度对路基承载力的影响。Abstract: To investigate the reinforcement mechanism of cement-fly ash post-grouting on pile-net composite subgrade in collapsible loess areas, the static load tests in laboratory were carried out on the grouted cement-fly ash gravel (CFG) piles, the influence of post-grouting on the collapsibility coefficient of the soil samples around the piles was analyzed, and the changing rules of additional stress, pile side friction resistance and pile tip resistance in the depth direction of post-grouting pile-net composite subgrade under vertical static load were studied. Based on the Boltzmann mathematical model and load transfer function, the reinforcement mechanism of pile side friction resistance and pile tip resistance was investigated, and their calculation formulas after grouting were given. The influence mechanisms of elastic modulus of pile, post-grouting depth, pile-net replacement rate, and cushion layer thickness on the bearing capacity of pile-net composite subgrade were discussed by the numerical simulation method. Research results indicate that under the same static load, the collapsibility coefficient of the cement-fly ash post-grouting soil around the pile is less than that of the natural soil sample and less than 0.015. After post-grouting, the vertical additional stress of the pile top in the pile-net composite subgrade gradually decreases under the static load, the vertical additional stress of the soil between the piles decreases first and then increases, and the pile side friction resistance increases by about 1.54 times compared with the un-grouting pile. With the increase in post-grouting depth, the maximum stress in the depth direction of pile body increases first and then decreases, and the maximum stress is obtained at the depth equal to pile length. When the pile-net replacement rate is doubled, the stress and settlement decrease in the depth direction, among which the peak stress decreases by 24% and settlement decreases by 26%. With the increase in cushion layer thickness in the pile-net composite subgrade, the stress in the depth direction of the subgrade gradually increases. Therefore, the cement-fly ash treatment of collapsible loess subgrade can weaken the collapsibility of subgrade soil and improve the bearing capacity. In the construction process, the effects of elastic modulus of pile, post-grouting depth, pile-net replacement rate and cushion thickness on the bearing capacity of the subgrade should be considered.
-
图 9 桩侧摩阻力-桩土相对位移曲线
Figure 9. Curves of pile side friction resistance and pile-soil relative displacement
图 10 桩端阻力-桩土相对位移曲线
Figure 10. Curves of pile tip resistance and pile-soil relative displacement
图 13 注浆深度不同时桩网结构路基深度-应力曲线
Figure 13. Depth-stress curves of pile-net composite subgrades with different grouting depths
图 14 置换率不同时桩网结构路基深度-应力曲线
Figure 14. Depth-settlement curves of pile-net composite subgrades with different replacement rates
图 15 置换率不同时桩网结构路基深度-沉降曲线
Figure 15. Depth-settlement curves of pile-net composite subgrades with different replacement rates
图 16 褥垫层厚度不同时桩网结构路基深度-应力曲线
Figure 16. Depth-stress curves of pile-net composite subgrades with different cushion layer
表 1 参数相似关系
Table 1. Similarity relations of parameters
物理量 相似系数 长度/m 10 质量/kg 100 应力/Pa 1 位移/m 10 弹性模量/MPa 1 泊松比 1 
下载: 导出CSV
表 2 黄土物理力学参数
Table 2. Physical and mechanical parameters of loess
土的分类 密度/(g·cm-3) 黏聚力/kPa 摩擦角/(°) 压缩模量/MPa 泊松比 粉质黏土 1.78 44.27 29.64 5.8 0.25
下载: 导出CSV
表 3 粉煤灰化学成分
Table 3. Chemical compositions of fly ash
成分 SiO2 Al2O3 Fe2O3 CaO MgO SO3 其他 百分比/% 62.76 23.73 4.02 3.56 2.62 2.79 0.52
下载: 导出CSV
表 4 粉煤灰物理性质
Table 4. Physical properties of fly ash
项目 国家标准 检验结果 Ⅰ级 Ⅱ级 Ⅲ级 细度(45 μm筛余/%) ≤12 ≤20 ≤45 19.8 需水量比/% ≤95 ≤105 ≤115 105 烧失量/% ≤5 ≤8 ≤15 2.0 含水率/% ≤1 ≤1 - 0.9 SO3含量/% ≤3 ≤3 ≤3 2.7
下载: 导出CSV
表 5 水泥的主要物理力学指标
Table 5. Main physical and mechanical indexes of cement
比表面积/(m2·kg-1) 安定性/mm 凝结时间/min 强度/MPa 初凝 终凝 3 d 28 d 357 3.6 65 470 18.1 43.6
下载: 导出CSV
表 6 模型桩与湿陷性黄土物理力学参数
Table 6. Physical and mechanical parameters of model pile and collapsible loess
材料类别 弹性模量/MPa 泊松比 重度/(kN·m-3) 黏聚力/kPa 内摩擦角/(°) 深度/m 湿陷性黄土(修正前) 12 0.25 15.9 27 13.3 0~6 湿陷性黄土(修正后) 6 0.25 17.9 27 13.3 0~6 粉质黏土 12 0.25 17.9 30 26.0 6~20 注浆水泥粉煤灰加固桩 12 000 0.20 21.3 6
下载: 导出CSV
表 7 桩网结构路基不同深度处沉降
Table 7. Settlements of different depths of pile-net composite subgrade
深度/m 沉降/mm 深度/m 沉降/mm E=1.2 GPa E=2.4 GPa E=1.2 GPa E=2.4 GPa 0.0 0.85 6.43 3.0 4.85 8.41 0.5 1.19 6.63 3.5 6.00 9.00 1.0 1.66 6.89 4.0 7.45 9.67 1.5 2.21 7.16 4.5 8.86 10.46 2.0 2.91 7.51 5.0 10.29 11.21 2.5 3.83 7.96 5.5 11.66 11.93
下载: 导出CSV
-
[1] 盛明强, 乾增珍, 杨文智, 等. 浸水饱和条件下黄土微型桩抗压和抗拔承载力试验[J]. 岩土工程学报, 2021, 43(12): 2258-2264. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC202112012.htmSHENG Ming-qiang, QIAN Zeng-zhen, YANG Wen-zhi, et al. Field compression and uplift tests on micropiles in collapsible loess under completely-soaked and saturated conditions[J]. Chinese Journal of Geotechnical Engineering, 2021, 43(12): 2258-2264. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC202112012.htm [2] 张延杰, 王旭, 梁庆国, 等. 浸水条件下湿陷性黄土地基群桩基础承载特性模型试验研究[J]. 岩土工程学报, 2021, 43(增1): 219-223. doi: 10.11779/CJGE2021S1040ZHANG Yan-jie, WANG Xu, LIANG Qing-guo, et al. Model tests on bearing behavior of pile groups in collapsible loess ground under water immersion[J]. Chinese Journal of Geotechnical Engineering, 2021, 43(S1): 219-223. (in Chinese) doi: 10.11779/CJGE2021S1040 [3] 杨重存. 黄土固化技术在公路工程中的应用及试验研究[D]. 西安: 长安大学, 2000.YANG Chong-cun. Application and experimental study of loess solidification technology in highway engineering[D]. Xi'an: Chang'an University, 2000. (in Chinese) [4] 邓友生, 李龙, 刘俊聪, 等. 波纹塑料套管煤矸石CFG桩复合路基承载试验[J]. 中国公路学报, 2023, 36(4): 48-57. https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL202304005.htmDENG You-sheng, LI Long, LIU Jun-cong, et al. Load-bearing test on composite subgrade of coal gangue CFG pile with corrugated plastic[J]. China Journal of Highway and Transport, 2023, 36(4): 48-57. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL202304005.htm [5] 祁巧艳, 刘亚龙. 基于塑性理论的湿陷性黄土本构模型[J]. 兰州理工大学学报, 2015, 41(3): 117-121. doi: 10.13295/j.cnki.jlut.2015.03.025QI Qiao-yan, LIU Ya-long. Plastic theory-based wet-collapsible loess constitutive model[J]. Journal of Lanzhou University of Technology, 2015, 41(3): 117-121. (in Chinese) doi: 10.13295/j.cnki.jlut.2015.03.025 [6] 魏平, 魏静, 杨松林, 等. 高速铁路低路基桩网结构土工格栅动力特性[J]. 交通运输工程学报, 2017, 17(6): 19-27. https://www.cnki.com.cn/Article/CJFDTOTAL-JYGC201706006.htmWEI Ping, WEI Jing, YANG Song-lin, et al. Geogrid dynamic characteristics of pile-net structure in low subgrade of high-speed railway[J]. Journal of Traffic and Transportation Engineering, 2017, 17(6): 19-27. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-JYGC201706006.htm [7] 邓友生, 李龙, 赵衡, 等. 基于透明土的梅花桩沉桩挤土效应[J]. 湖南大学学报(自然科学版), 2022, 49(7): 205-213. https://www.cnki.com.cn/Article/CJFDTOTAL-HNDX202207021.htmDENG You-sheng, LI Long, ZHAO Heng, et al. Plum-blossom pile penetration effect based on transparent soil[J]. Journal of Hunan University (Natural Sciences), 2022, 49(7): 205-213. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-HNDX202207021.htm [8] 王永鑫, 邵生俊, 韩常领, 等. 湿陷性黄土砂井浸水试验的应用研究[J]. 岩土工程学报, 2018, 40(增1): 159-164, 7. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC2018S1027.htmWANG Yong-xin, SHAO Sheng-jun, HAN Chang-ling, et al. Application of sand drain immersion tests on collapsible loess[J]. Chinese Journal of Geotechnical Engineering, 2018, 40(S1): 159-164, 7. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC2018S1027.htm [9] WANG Jia-ding, ZHANG Deng-fei, ZHANG Yong-shuang, et al. Variations in hydraulic properties of collapsible loess exposed to wetting and shearing[J]. Acta Geotechnica, 2022, 17(7): 2995-3015. doi: 10.1007/s11440-021-01427-y [10] ZHAO Meng, WU Hong-gang, GUO Wei, et al. Experimental study of the particle agglomeration on its mechanical properties of collapsible loess[J]. Frontiers in Earth Science, 2022, 10: 943383. doi: 10.3389/feart.2022.943383 [11] 穆青翼, 党影杰, 董琪, 等. 原状和压实黄土持水特性及湿陷性对比试验研究[J]. 岩土工程学报, 2019, 41(8): 1496-1504. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201908017.htmMU Qing-yi, DANG Ying-jie, DONG Qi, et al. Water-retention characteristics and collapsibity behaviors: comparison between intact and compacted loesses[J]. Chinese Journal of Geotechnical Engineering, 2019, 41(8): 1496-1504. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201908017.htm [12] 苏忍, 张恒睿, 张稳军, 等. 兰州地铁大厚度湿陷性黄土地层的现场浸水试验研究[J]. 土木工程学报, 2020, 53(增1): 186-193. https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC2020S1030.htmSU Ren, ZHANG Heng-rui, ZHANG Wen-jun, et al. Immersion tests on self-weight collapsible loess site with large depth of Lanzhou metro line[J]. China Civil Engineering Journal, 2020, 53(S1): 186-193. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC2020S1030.htm [13] 徐硕昌, 刘德仁, 王旭, 等. 兰州新区大厚度湿陷性黄土宏细观参数试验研究[J]. 铁道科学与工程学报, 2022, 19(7): 1918-1926. https://www.cnki.com.cn/Article/CJFDTOTAL-CSTD202207014.htmXU Shuo-chang, LIU De-ren, WANG Xu, et al. Experimental study on macro and meso parameters of large thickness collapsible loess in Lanzhou New District[J]. Journal of Railway Science and Engineering, 2022, 19(7): 1918-1926. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-CSTD202207014.htm [14] 吴会东. 山西北部地区黄土湿陷性快速判定方法研究[J]. 铁道工程学报, 2021, 38(2): 35-40. https://www.cnki.com.cn/Article/CJFDTOTAL-TDGC202102007.htmWU Hui-dong. Research on a fast judgement method of loess collapsibility in northern Shanxi[J]. Journal of Railway Engineering Society, 2021, 38(2): 35-40. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-TDGC202102007.htm [15] ZHENG Zi-yu, LI Xi-an, WANG Li, et al. A new approach to evaluation of loess collapsibility based on quantitative analyses of colloid-clay coating with statistical methods[J]. Engineering Geology, 2021, 288: 106167. [16] ZHANG Yan-jie, HAN Jian-long, WANG Xu, et al. Evaluation of loess collapsibility based on random field theory in Xi'an, China[J]. Mathematical Problems in Engineering, 2022, 2022: 8665061. [17] ZHONG Xiu-mei, LIANG Yu-xin, WANG Qian, et al. Evaluation and analysis of the effect of lignin amelioration on loess collapsibility[J]. Journal of Renewable Materials, 2022, 10(12): 3405-3424. [18] HANNA A, SOLIMAN S. Experimental investigation of foundation on collapsible soils[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2017, 143(11): 04017085. [19] ZHANG Yang, JOHNSON A E, WHITE D J. Freeze-thaw performance of cement and fly ash stabilized loess[J]. Transportation Geotechnics, 2019, 21: 100279. [20] 崔自治, 朱楠, 王晓芸. 黄土自重湿陷性评价的理论与试验研究[J]. 兰州理工大学学报, 2013, 39(6): 115-117. https://www.cnki.com.cn/Article/CJFDTOTAL-GSGY201306026.htmCUI Zi-zhi, ZHU Nan, WANG Xiao-yun. Theoretical and experimental research on evaluation of loess collapsible under overburden pressure[J]. Journal of Lanzhou University of Technology, 2013, 39(6): 115-117. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-GSGY201306026.htm [21] 崔靖俞. 工业废料注浆加固湿陷性黄土的试验研究[D]. 西宁: 青海大学, 2020.CUI Jing-yu. Experimental study on grouting reinforcement of collapsible loess by industrial waste[D]. Xining: Qinghai University, 2020. (in Chinese) [22] 朱苗淼, 朱武卫. 矿渣与工业废渣改良黄土的性能与机理研究进展[J]. 灾害学, 2022, 37(1): 129-133. https://www.cnki.com.cn/Article/CJFDTOTAL-ZHXU202201022.htmZHU Miao-miao, ZHU Wu-wei. Research progress on properties and mechanism of loess modified by slag and industrial waste residue[J]. Journal of Catastrophology, 2022, 37(1): 129-133. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-ZHXU202201022.htm [23] MEI Yuan, ZHANG Shu-min, HU Chang-ming, et al. Field test study on dynamic compaction in treatment of a deep collapsible loess foundation[J]. Bulletin of Engineering Geology and the Environment, 2021, 80(10): 8059-8073. [24] 张恩祥, 何腊平, 龙照, 等. 黄土地区刚-柔性桩复合地基的承载机理[J]. 交通运输工程学报, 2019, 19(4): 70-80. doi: 10.19818/j.cnki.1671-1637.2019.04.007ZHANG En-xiang, HE La-ping, LONG Zhao, et al. Bearing mechanism of composite foundation with rigid-flexible piles in loess area[J]. Journal of Traffic and Transportation Engineering, 2019, 19(4): 70-80. (in Chinese) doi: 10.19818/j.cnki.1671-1637.2019.04.007 [25] 周志军, 徐天宇, 徐甫, 等. 黄土地区不同成孔方式灌注桩压浆前后承载特性[J]. 交通运输工程学报, 2021, 21(4): 84-93. doi: 10.19818/j.cnki.1671-1637.2021.04.005ZHOU Zhi-jun, XU Tian-yu, XU Fu, et al. Bearing characteristics of cast-in-place piles with different hole-forming methods before and after grouting in loess area[J]. Journal of Traffic and Transportation Engineering, 2021, 21(4): 84-93. (in Chinese) doi: 10.19818/j.cnki.1671-1637.2021.04.005 [26] 熊彩凤, 徐甫, 冯泓鸣, 等. 黄土地区桥梁灌注桩桩端后注浆优化室内模型试验研究[J]. 铁道科学与工程学报, 2022, 19(6): 1585-1593. https://www.cnki.com.cn/Article/CJFDTOTAL-CSTD202206013.htmXIONG Cai-feng, XU Fu, FENG Hong-ming, et al. Laboratory model test study on optimization of post grouting at the end of bridge cast-in-place pile in loess area[J]. Journal of Railway Science and Engineering, 2022, 19(6): 1585-1593. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-CSTD202206013.htm [27] 贾剑青, 赵阳阳, 贾超, 等. 湿陷性黄土地基水泥土搅拌桩加固效果研究[J]. 铁道工程学报, 2022, 39(7): 18-24. https://www.cnki.com.cn/Article/CJFDTOTAL-TDGC202207003.htmJIA Jian-qing, ZHAO Yang-yang, JIA Chao, et al. Research on the reinforcement effect of cement-soil mixing pile on collapsible loess foundation[J]. Journal of Railway Engineering Society, 2022, 39(7): 18-24. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-TDGC202207003.htm [28] 马天忠, 孙晨东, 高玉广, 等. 浸水状态下湿陷性黄土场地螺旋灌注桩负摩阻力与土体湿陷规律试验[J]. 中国公路学报, 2022, 35(8): 151-161. https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL202208014.htmMA Tian-zhong, SUN Chen-dong, GAO Yu-guang, et al. Experimental analysis on negative friction resistance of spiral cast-in-place piles and soil collapse law in collapsible loess site[J]. China Journal of Highway and Transport, 2022, 35(8): 151-161. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-ZGGL202208014.htm [29] HOU Jian, LU Yi-yang, WANG Jian-an, et al. Calculation model of compaction coefficient of soil among SP-PSC pile group on collapsible loess foundation[J]. Applied Sciences, 2023, 13(6): 4003. [30] YE Shuai-hua, ZHAO Zhuang-fu, ZHU Yan-peng. Study on negative friction of pile foundation in single homogeneous soil layer in collapsible loess area of northwest China[J]. Arabian Journal of Geosciences, 2021, 14(12): 1137. [31] PHOAK S, LUO Ya-sheng, LI Sheng-nan. Influence of submergence on stabilization of loess in Shaanxi province by adding fly ash[J]. Applied Sciences, 2019, 9(1): 68. [32] 肖宏彬. 竖向荷载作用下大直径桩的荷载传递理论及应用研究[D]. 长沙: 中南大学, 2005.XIAO Hong-bin. Theoretical and application research on load transfer of vertically loading large diameter piles[D]. Changsha: Central South University, 2005. (in Chinese) [33] 陈仁朋, 陈金苗, 汪焱卫, 等. 桩网结构路基应力传递特性及累积沉降规律[J]. 土木工程学报, 2015, 48(增2): 241-245. https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC2015S2044.htmCHEN Ren-peng, CHEN Jin-miao, WANG Yan-wei, et al. Stress transmission and cumulative settlement characteristics of geogrid reinforced pile supported embankment[J]. China Civil Engineering Journal, 2015, 48(S2): 241-245. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC2015S2044.htm [34] 万志辉, 戴国亮, 龚维明, 等. 基于自平衡法后压浆灌注桩荷载传递函数的变化分析[J]. 土木工程学报, 2017, 50(8): 98-104. https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC201708011.htmWAN Zhi-hui, DAI Guo-liang, GONG Wei-ming, et al. Analysis on the load transfer function of post-grouting bored pile based on self-balanced method[J]. China Civil Engineering Journal, 2017, 50(8): 98-104. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC201708011.htm [35] 万志辉, 戴国亮, 龚维明. 超厚细砂地层大直径后压浆桩荷载传递计算与分析[J]. 岩土力学, 2018, 39(4): 1386-1394. https://www.cnki.com.cn/Article/CJFDTOTAL-YTLX201804031.htmWAN Zhi-hui, DAI Guo-liang, GONG Wei-ming. Calculation and analysis of load transfer in large-diameter grouted pile in extra-thick fine sand layers[J]. Rock and Soil Mechanics, 2018, 39(4): 1386-1394. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTLX201804031.htm [36] RUIZ M E, PANDO M A. Load transfer mechanisms of tip post-grouted drilled shafts in sand[C]//ASCE. Proceedings of International Foundation Congress and Equipment Expo. Reston: ASCE, 2009: 23-30. -
点击查看大图
图(16) / 表(7)
计量
- 文章访问数: 633
- HTML全文浏览量: 218
- PDF下载量: 84
- 被引次数: 0
