Fig 1.
Maximum structural fracture of (a) deep hard roadway; and (b) deep soft roadway.
Fig 2.
Drilling histogram near (a) cross point 1; and (b) cross point 2.
Fig 3.
In-situ rock samples.
Table 1.
Strength of rock samples at different cross points.
Fig 4.
Mechanical structure model of (a) cross point 1; and (b) cross point 2.
Fig 5.
Multi-echelon support of surrounding rock.
Fig 6.
Plane strain test rig model of (a) cross point 1; and (b) cross point 2.
Fig 7.
Similar material standard rock samples of the (a) first group; (b) second group; and (c) third group.
Table 2.
Mechanical parameters of the similar material.
Fig 8.
Figure about (a) making roadway model; and (b) laying strain gauge.
Fig 9.
Multi-echelon support design of (a) excavation roadway; (b) first-layer support; (c) second-layer support; and (d) third-layer support.
Fig 10.
Multi-echelon support and strain gauge layout.
Table 3.
Loading stress of jack in different cross points.
Fig 11.
Bearing structure in cross point 1 without support when the horizontal press coefficient is (a) λ = 1; (b) λ = 1.5; and (c) λ = 2.
Fig 12.
Bearing structure in cross point 2 without support when the horizontal press coefficient is (a) λ = 1; (b) λ = 1.5; and (c) λ = 2.
Table 4.
Thickness of bearing structure without support.
Fig 13.
Multi-echelon support design of the cross point 1 when the horizontal press coefficient is (a) λ = 1; (b) λ = 1.5; and (c) λ = 2.
Fig 14.
Multi-echelon support design of the cross point 2 when the horizontal press coefficient is (a) λ = 1; (b) λ = 1.5; and (c) λ = 2.
Fig 15.
Bearing structure of the cross point 1 under multi-echelon support when the horizontal press coefficient is (a) λ = 1; (b) λ = 1.5; and (c) λ = 2.
Fig 16.
Bearing structure of the cross point 2 under multi-echelon support when the horizontal press coefficient is (a) λ = 1; (b) λ = 1.5; and (c) λ = 2.
Table 5.
Scope of bearing structure under multi-echelon support.
Fig 17.
Concentration degree of tangential stress in cross point 1 (a) without support and (b) with multi-echelon support.
Fig 18.
Concentration degree of tangential stress in cross point 2 (a) without support and (b) with multi-echelon support.
Fig 19.
Surrounding rock burst development in cross point 1 without support when horizontal press coefficient is (a) λ = 1; (b) λ = 1.5; and (c) λ = 2.
Fig 20.
Surrounding rock burst development in cross point 1 with multi-echelon support when horizontal press coefficient is (a) λ = 1; (b) λ = 1.5; and (c) λ = 2.
Fig 21.
Surrounding rock burst development in cross point 2 without support when horizontal press coefficient is (a) λ = 1; (b) λ = 1.5; and (c) λ = 2.
Fig 22.
Surrounding rock burst development in cross point 2 with multi-echelon support when horizontal press coefficient is (a) λ = 1; (b) λ = 1.5; and (c) λ = 2.
Table 6.
Convergence value of different cross points.
Table 7.
Range of fracture zones of surrounding rock.
Fig 23.
Loosing circle in cross point 1 (a) without support; (b) with multi-echelon support.
Fig 24.
Loosing circle in cross point 2 (a) without support; (b) with multi-echelon support.
Fig 25.
Grouting effect of multi-echelon support in (a) cross point 1; (b) cross point 2.
Fig 26.
Loosing circle in cross point 1 (a) without support; (b) with multi-echelon support.
Fig 27.
Loosing circle in cross point 2 (a) without support; (b) with multi-echelon support.