A Study on the Seepage Flow Characteristics and Disaster-Causing Mechanism of Collapse Column

Table 1

Permeability coefficients of broken sandstone and broken mudstone/ = 5.6  × 10⁻⁵ m·s⁻¹.

Particle sizes and axial pressure		Broken sandstone (×10^−8 m·s^−1)				Broken mudstone (×10^−10 m·s^−1)
		1	2	4	6	1	2	4	6
Φ = 15–20 mm	11	154.76	151.66	149.52	137.34	175.14	157.15	154.86	126.26
	22	121.25	116.71	117.13	41.98	34.92	48.06	33.15	29.85
	33	69.56	23.27	12.45	3.33	14.04	17.67	16.86	3.17
	44	1.37	1.06	0.73	0.51	2.95	2.05	2.55	1.45
Φ = 10–15 mm	11	82.69	77.89	75.4	62.72	251.47	201.36	140.77	140.82
	22	20.75	8.92	9.43	7.63	89.44	65.08	47.11	21.86
	33	1.19	1.01	0.92	0.89	6.39	5.56	3.04	1.78
	44	1.24	0.62	0.56	0.52	1.45	0.97	0.58	0.66
Φ = 5–10 mm	11	44.32	40.78	35.12	30.63	52.84	42.7	36.37	29.92
	22	15.6	7.12	6.98	5.3	25.12	23.92	19.12	12.84
	33	1.08	0.87	0.68	0.54	9.7	8.67	7.89	5.3
	44	0.79	0.54	0.51	0.48	2.07	1.77	1.25	1.23
Φ = 2.5–5 mm	11	15.27	12.02	9.42	8.69	36.26	32.18	25.52	20.77
	22	1.8	1.79	1.16	0.92	9.87	8.35	7.23	6.19
	33	0.49	0.33	0.32	0.28	3.02	2.31	2.05	1.75
	44	0.23	0.19	0.17	0.14	0.93	0.74	0.66	0.54
Mixture of different particle sizes: 1 : 1 : 1 : 1	11	7.04	5.76	4.72	3.24	16.05	13.47	10.85	7.72
	22	1.42	1.29	1.09	0.84	6.48	5	4.13	3.87
	33	0.37	0.31	0.28	0.24	2.12	1.78	1.55	0.98
	44	0.17	0.15	0.14	0.11	0.55	0.43	0.33	0.29