Bearing behavior of inclined pile for transmission towers in loess soils under immersion

doi:10.16265/j.cnki.issn1003-3033.2025.03.1128

Abstract

Abstract:

To improve the application of small-angle inclined piles in collapsible loess areas, finite element models of 2×2 pile groups with three different inclination angles were established. The modulus reduction method was employed to simulate the collapsibility effect of loess, and the influence of loading and soaking sequences on the bearing characteristics of pile groups with different inclination angles was analyzed. The results indicate that, based on the conducted tests of 0, 10 and 15° pile groups, under both loading-before-soaking and soaking-before-loading conditions, the displacement of the pile cap and the settlement of the surrounding foundation soil are smaller for inclined pile groups compared to vertical pile groups. Moreover, the inclined pile group is less affected by the water-induced collapsibility of loess. However, the bending moment and shear force of the inclined piles are higher than those of the vertical piles. Compared to the loading-before-soaking condition, the soaking-before-loading condition results in smaller pile cap displacements and soil settlements but larger internal forces in the inclined pile shafts. Additionally, the shaft friction of inclined piles is smaller under the soaking-before-loading condition. Inclined pile groups with larger inclination angles demonstrate superior load-bearing capacity and resistance to loess collapsibility induced by soaking. Pre-soaking treatment of loess foundations effectively enhances the ultimate bearing capacity of pile group foundations.

Key words: collapsible loess, transmission towers, inclined pile group, ultimate bearing capacity, numerical simulation

CLC Number:

X946

ZHU Yulong, CAO Weiping, LYU Pin, WANG Yue, ZHAO Min. Bearing behavior of inclined pile for transmission towers in loess soils under immersion[J]. China Safety Science Journal, 2025, 35(3): 169-178.

Figures/Tables 15

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层号	层底深度/m	含水率/%	天然重度/ (kN·m^-3)	饱和重度/ (kN·m^-3)	天然孔隙比	饱和度/%	变形模量/MPa	折减系数	折减后变形模量/MPa	自重湿陷系数	湿陷系数
L₁	5.2	16	14.3	17.2	1.19	36	6	0.8	4.8	0.017	0.085
F₁	6.4	16	17.5	19.0	0.80	54	30	0.8	24	0.004	0.025
L₂	10.4	17	17.0	18.7	0.86	53	38	0.8	30.4	0.006	0.040
F₂	13.8	17	17.6	19.0	0.80	58	30	0.8	24	0.015	0.025
L₃	19.9	16	16.5	18.5	0.90	48	15	0.8	12	0.030	0.040
F₃	21.4	16	17.5	19.0	0.80	54	38	0.8	30.4	0.015	0.020
L₄	26.5	16	16.8	19.0	0.93	47	18	0.8	14.4	0.020	0.030
F₄	27.4	16	18.0	18.3	0.75	58	30	0.8	24	0.015	0.015
L₅	33.3	17	17.2	19.3	0.84	55	27	0.8	21.6	0.020	0.023
F₅	35.2	17	18.5	18.8	0.72	64	54	0.8	43.2	0.015	0.015
L₆	39.0	17	18.5	19.5	0.72	64	48	0.8	38.4	0.007	0.008
F₇	60	14	19.0	19.5	0.66	70	80	1	80	0.008	0.004

组号	桩身倾角/(°)			荷载最大值/kN		工况
组号	①	②	③	下压荷载	水平荷载	工况
T1	0/10/15			3 000	—	天然湿密状态
T2	0/10/15			—	600	天然湿密状态
T3	0/10/15			1/2V_u	1/2H_u	先加载后浸水
T4	0/10/15			1/2V_u	1/2H_u	先浸水后加载

工况	0°直群桩		10°斜群桩		15°斜群桩
工况	先加载	先浸水	先加载	先浸水	先加载	先浸水
水平	13.86	6.49	9.35	5.02	4.27	2.85
竖向	10.80	10.54	10.21	9.81	8.24	8.08

工况	0°直群桩		10°斜群桩		15°斜群桩
工况	先加载	先浸水	先加载	先浸水	先加载	先浸水
A点	10.61	6.74	9.59	6.58	8.18	4.68
B点	8.93	5.49	8.35	5.20	7.20	3.77
C点	11.50	10.57	11.26	10.00	9.54	8.44

工况	0°直群桩		10°斜群桩		15°斜群桩
工况	先加载	先浸水	先加载	先浸水	先加载	先浸水
前排桩	55	36	-49	-62	-55	-85
后排桩	112	38	99	109	83	121