Experimental studies on the effects of bolt parameters on the bearing characteristics of reinforced rock

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Table 2 The measured stress of the composite rock-bolt bearing structure and acceleration rate of surrounding rock displacement

Distance between bolts/mm	Second stage			Third stage			Percentage of stress decrease (%)
Distance between bolts/mm	Kinetic pressure coefficient range	Peak stress/MPa	Vertical closure acceleration rate of displacement/mm/MPa	Kinetic pressure coefficient range	Residual sress/MPa	Vertical closure acceleration rate of displacement/mm/MPa	Percentage of stress decrease (%)
(a) Vertical stress at Sensor 1
No bolts	0.50–1.00	0.008	14.4	1.00–1.23	0.004	25.2	50.0
1000	0.50–1.24	0.018	12.6	1.24–1.47	0.010	20.4	44.4
800	0.50–1.95	0.049	7.2	1.95–2.42	0.029	14.9	40.8
600	0.50–2.66	0.069	7.2	2.66– 2.89	0.065	14.8	5.8

Distance between bolts/mm	Second stage			Third stage			Percentage of stress decrease (%)
Distance between bolts/mm	Kinetic pressure coefficient range	Peak stress/MPa	Rib convergence closure acceleration rate of displacement/mm/MPa	Kinetic pressure coefficient range	Residual sress/MPa	Rib convergence closure acceleration rate of displacement/mm/MPa	Percentage of stress decrease (%)
(b) Vertical stress at Sensor 2
No bolts	0.50–1.00	0.114	12.0	1.00––1.23	0.052	15.2	54.4
1000	0.50–1.24	0.200	7.6	1.24–1.47	0.162	14.3	19.0
800	0.50–1.71	0.505	4.4	1.71–2.42	0.452	12.7	10.5
600	0.50–2.66	0.629	3.7	2.66–2.89	0.567	10.9	9.9

Distance between bolts/mm	Second stage			Third stage			Percentage of stress decrease (%)
Distance between bolts/mm	Kinetic pressure coefficient range	Peak stress/MPa	Vertical closure acceleration rate of displacement/mm/MPa	Kinetic pressure coefficient range	Residual sress/MPa	Vertical closure acceleration rate of displacement/mm/MPa	Percentage of stress decrease (%)
(c) Horizontal stress at Sensor 1
No bolts	0.50–1.00	0.060	14.4	1.00–1.23	0.012	25.2	80.0
1000	0.50–1.24	0.080	12.6	1.24–1.47	0.040	20.4	50.0
800	0.50–1.95	0.150	7.2	1.95–2.42	0.100	14.9	33.3
600	0.50–2.19	0.187	6.7	2.19–2.89	0.157	10.7	16.0

Distance between bolts/mm	Second stage			Third stage			Percentage of stress decrease (%)
Distance between bolts/mm	Kinetic pressure coefficient range	Peak stress/MPa	Rib convergence closure acceleration rate of displacement/mm/MPa	Kinetic pressure coefficient range	Residual sress/MPa	Rib convergence closure acceleration rate of displacement/mm/MPa	Percentage of stress decrease (%)
(d) Horizontal stress at Sensor 2
No bolts	0.50–1.00	0.009	12.0	1.00–1.23	0.006	15.2	33.3
1000	0.50–1.24	0.027	7.6	1.24–1.47	0.019	14.3	29.6
800	0.50–1.95	0.080	5.6	1.95–2.42	0.058	13.2	27.5
600	0.50–2.66	0.095	3.7	2.66–2.89	0.082	10.9	13.7

(1)The peak stress is the maximum stress in the second stage; (2) The residual stress is the minimum stress in the third stage; (3) The percentage of stress decrease is the percentage of decrease from the peak to residual stress