SHENG Ming-qiang, QIAN Zeng-zhen, YANG Wen-zhi, LU Xian-long. 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. DOI: 10.11779/CJGE202112012
Citation:
SHENG Ming-qiang, QIAN Zeng-zhen, YANG Wen-zhi, LU Xian-long. 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. DOI: 10.11779/CJGE202112012
Abstract:
In order to investigate the compression and uplift bearing capacity of micropiles in collapsible loess, a method for loess prewetting under completely soaked and saturated conditions is firstly designed. Consequently, the comparative field compression and uplift load tests on single micropile and group micropiles are respectively carried out in the two collapsible loess sites in Gansu Province. Both the site conditions and the load tests are documented comprehensively. The compression and uplift load-displacement curves of the single micropile and group micropiles in completely soaked and saturated loess generally follow a typical two-phase steep change pattern, which is quite different from those in-situ moisture content loess because they can be simplified into three distinct regions: initially linear, curvilinear transition and finally linear regions. Both in the in-situ moisture content loess and the completely soaked and saturated loess, the compression or uplift loaded single micropiles should be considered as the frictional pile foundations, and the tip resistances are only about 10% to 15% of the applied compression loads. For the micropiles in loess under in-situ moisture content, the ultimate uplift load capacities are 66% to 87% of those under compression. However, the loess under completely soaked and saturated condition will lead to a reduction of 70% in compressive bearing capacity and 50% in uplift bearing capacity for single micropile, and that for group micropiles is about 75% in compressive bearing capacity. These experimental results may provide a reference for the designers in loess in the future.
QIAO Jian-wei, ZHENG Jian-guo, LIU Zheng-hong, et al. The distribution and major engineering problems of special soil and rock along one belt one road[J]. Journal of Catastrophology, 2019, 34(S1): 65-71. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-ZHXU2019S1012.htm
ZHU Yan-peng, YANG Kui-bin, WANG Hai-ming, et al. Preliminary exploration of tests on effect of micro-immersion on negative skin friction of pile foundation[J]. Chinese Journal of Geotechnical Engineering, 2018, 40(S1): 1-7. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC2018S1002.htm
HUANG Xue-feng, CHEN Zheng-han, HA Shuang et al. Research on bearing behaviors and negative friction force for filling piles in the site of collapsible loess with big thickness[J]. Chinese Journal of Geotechnical Engineering, 2007, 29(3): 338-346. (in Chinese) doi: 10.3321/j.issn:1000-4548.2007.03.005
LI Da-zhan, TENG Yan-jing, HE Yi-hua, et al. Vertical bearing behaviour of large diameter belled pile in collapsible loess[J]. Chinese Journal of Geotechnical Engineering, 1994, 16(2): 11-21. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC402.001.htm
LIU San-cang, SUI Guo-xiu, LIU Zhi-wei. Research on bearing capacity of cast-in-place piles in unsaturated to saturated loess[J]. Chinese Journal of Geotechnical Engineering, 2007, 29(1): 147-151. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC200701025.htm
ARMOURTGRONECKPKEELEYJMicropile design and construction guidelines implementation manual priority technologies program (PTP) projectReport No. FHWA-SA-97-070Washington D CDepartment of Transportation Federal Highway20003233
ARMOUR T, GRONECK P, KEELEY J, et al. Micropile design and construction guidelines implementation manual priority technologies program (PTP) project[R]. Report No. FHWA-SA-97-070. Washington D C: Department of Transportation Federal Highway, 2000: 32-33.
[9]
CADDEN A, GÓMEZ J, BRUCE D, et al. Micropiles: recent advances and future trends[C]//Current Practices and Future Trends in Deep Foundations, ASCE, 2004: 140-165. Los Angeles,
ZHOU Jun-peng, HUANG Xue-feng, LIU Zi-long, et al. Experimental study of micro compression and uplift pile in loess foundation[J]. Journal of Water Resources and Architectural Engineering, 2017, 15(1): 121-125. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-FSJS201701022.htm
WU Xiao-peng, WANG Lan-min, FANG Jian-hong, et al. Seepage characteristics and their relationship with self-weight collapse of intact loess ground[J]. Chinese Journal of Geotechnical Engineering, 2018, 40(6): 1002-1010. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201806006.htm
HUANG Xue-feng, CHEN Zheng-han, HA shuang, et al. Large area field immersion tests on characteristics of deformation of self-weight collapse loess under overburden pressure[J]. Chinese Journal of Geotechnical Engineering, 2006, 28(3): 382-389. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC200603023.htm
SHAO Sheng-jun, LI Jun, SHAO Jiang, et al. In-situ sand well immersion tests on self-weight collapsible loess site with large depth[J]. Chinese Journal of Geotechnical Engineering, 2016, 38(9): 1549-1558. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201609002.htm
ZHANG Yan-jie, LI Jian-dong, WANG Xu, et al. Soaking test on underground diaphragm wall in artificially prepared collapsible loess foundation[J]. Chinese Journal of Geotechnical Engineering 2018, 40(S1): 73-80. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC2018S1013.htm
ZHANG Xi, LIU Sheng-kui, LI Yong-xiang. Design optimization and water immersion static load test on undisturbed soil column foundation in collapsible loess soil[J]. Electric Power Construction, 2013, 34(5): 17-21. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-DLJS201305007.htm
HUANG Guang-long, FANG Qian, SU Rong-zhen. Field test on uplift behavior of micropiles in soft ground[J]. Chinese Journal of Geotechnical Engineering, 2010, 32(11): 1788-1793. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC201011028.htm
LÜ Fan-ren, CHEN Ren-peng, CHEN Yun-min, et al. Field tests on compression and uplift behavior of micropiles in soft ground[J]. China Civil Engineering Journal, 2005, 38(3): 99-105. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC200503015.htm
[18]
QIAN Z Z, LU X L. Behavior of micropiles in soft soil under vertical loading[J]. Advanced Materials Research, 2011, 243/244/245/246/247/248/249: 2143-2150.
[19]
HAN J, YE S L. A field study on the behavior of micropiles in clay under compression or tension[J]. Canadian Geotechnical Journal, 2006, 43(1): 19-29.