Influence of asperity shapes on friction coefficients of sandstone joints

doi:10.16265/j.cnki.issn1003-3033.2022.04.006

Abstract

Abstract:

In order to analyze influence of asperity shapes on sliding stability of sandstones, a sliding friction test was performed on a self-made device. With asperity shapes of sandstone surface being considered as a regular polygon and asperity shape coefficient being introduced, a prediction model for friction coefficients of sandstone joints, including asperities, was proposed. The results indicate that along with increase in asperity's length, friction coefficients gradually decrease, and their variation range becomes narrower. When the length is constant, friction coefficients gradually decrease with the increase of asperity shape coefficient. And in the case of constant asperity shape coefficient, friction coefficients gradually decrease with increase of length. The predicted friction coefficient is in good agreement with test value when the length is between 2-5 mm.

Key words: asperity shape, sandstone joint, friction coefficient, dilatancy angle, friction angle

WANG Laigui, ZHAO Guochao, LIU Xiangfeng, ZHAO Na, LI Xilin. Influence of asperity shapes on friction coefficients of sandstone joints[J]. China Safety Science Journal, 2022, 32(4): 36-43.

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微凸体长度λ/mm	1.11	1.25	1.43	1.67	2.0	2.50	3.33	5.0	10.0
正三棱锥	3.391	2.786	2.293	1.884	1.539	1.243	0.988	0.765	0.568
正四棱锥	1.827	1.602	1.399	1.215	1.048	0.895	0.754	0.625	0.505
正五棱锥	1.513	1.348	1.196	1.056	0.925	0.804	0.691	0.586	0.487
正六棱锥	1.386	1.243	1.111	0.988	0.873	0.765	0.664	0.568	0.479
圆锥	1.169	1.063	0.963	0.869	0.779	0.694	0.614	0.537	0.464

c,K值误差	K=1.0	K=1.2	K=1.4	K=1.6	K=1.8	K=2.0	K=2.2	K=2.4	K=2.6	K=2.8
c=1.0	9.18	7.23	5.72	4.94	4.65	4.63	4.80	5.62	7.28	9.04
c=1.2	7.49	5.42	4.39	4.20	4.31	4.56	5.80	7.68	9.56	11.44
c=1.4	5.77	3.99	3.72	4.00	4.38	5.89	7.89	9.88	11.88	14.05
c=1.6	4.04	3.33	3.64	4.22	5.77	7.89	10.01	12.28	14.61	16.94
c=1.8	2.95	3.22	4.01	5.44	7.68	10.02	12.48	14.95	17.41	19.87
c=2.0	2.75	3.70	5.05	7.26	9.86	12.46	15.06	17.66	20.26	22.86

微凸体形状	正三棱锥	正四棱锥	正五棱锥	正六棱锥	圆锥
微凸体长度/mm	5.0	3.33	3.33	2.5	2.0
第一次滑动初始剪胀角/(°)	15.91	15.52	13.15	15.91	16.42
基础摩擦角/(°)	21.5	21.5	21.5	21.5	21.5
K=1.0时误差/%	9.89	10.43	13.56	9.89	9.18
误差最小时c、K的取值	c=2.0,K=1.0	c=2.0,K=1.0	c=2.0,K=1.4	c=2.0,K=1.0	c=2.0,K=1.0
最小误差/%	2.74	2.85	3.30	2.74	2.75