Theoretical Solution to Borehole Contraction Caused by Unloading in Anisotropic Sandy Soil

FEI Yi; LI Wang-hui; ZHAO Chun-feng; WANG You-bao; WU Yue

doi:10.11988/ckyyb.20191118

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Journal of Changjiang River Scientific Research Institute ›› 2020, Vol. 37 ›› Issue (4) : 168-174. DOI: 10.11988/ckyyb.20191118

THE TENTH NATIONAL YOUTH CONFERENCE ON GEOMECHANICS AND GEOTECHNICAL ENGINEERING

Theoretical Solution to Borehole Contraction Caused by Unloading in Anisotropic Sandy Soil

FEI Yi¹, LI Wang-hui², ZHAO Chun-feng¹, WANG You-bao¹, WU Yue¹

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Abstract

Radial unloading-induced borehole contraction is caused in the drilling process of bored pile. On the basis of the SMP yield criterion and the non-correlated flow rule, the solution for the stress and displacement fields in two stress-state conditions of plastic zone around the vertical borehole is deduced with the coefficient K₀ of lateral earth pressure considered. Parameter analysis shows that the K₀ and internal friction angle φ of soil have a great influence on the emergence and development of plastic zone as well as the radius r_e and r_p of plastic zone. The relative displacement and stress of borehole wall increase linearly along with the increase of drilling depth with different values of K₀ and mud's unit weight r_mud. The relative displacement of borehole wall intensifies with the growth of K₀, while declines with the rising of r_mud. However, the radial and circumferential stresses of borehole wall do not change with K₀. In addition, the range of plastic zone around the vertical borehole hardly changes along the depth in sandy soil, and the plastic radius r_p has a remarkable influence on the circumferential stress. The theoretical solution presented in this paper is of theoretical significance for the unloading problem of borehole in initial in-situ stress field of sandy soil.

Key words

sand / cast-in-place pile / coefficient of lateral earth pressure / vertical drilling / radial unloading / theoretical solution

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FEI Yi, LI Wang-hui, ZHAO Chun-feng, WANG You-bao, WU Yue. Theoretical Solution to Borehole Contraction Caused by Unloading in Anisotropic Sandy Soil[J]. Journal of Changjiang River Scientific Research Institute. 2020, 37(4): 168-174 https://doi.org/10.11988/ckyyb.20191118

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