案例分析—用短壁开采的方式来回收煤柱毕业论文外文翻译(编辑修改稿)

案例分析—用短壁开采的方式来回收煤柱毕业论文外文翻译(编辑修改稿)内容摘要：

Models for extraction width of 5 pillars (104m) at a depth cover of 50m (30m hard cover+20m alluvial soil). Table 3 Calibrated properties Modulus of elasticity (Gpa) Poisson’s ratio RMR Rock mass pressive strength (Mpa) Rock mass tensile strength (Mpa) caol 50 BedⅠ 55 BedⅡ 65 BedⅢ 55 BedⅣ 70 BedⅤ amp。 Ⅵ ModelB: Models for extraction width of 4 pillars (84m) at a depth cover of 50m (30m hard cover+20m alluvial soil). ModelC: Models for extraction width of 4 pillars (84m) at a depth cover of 40m (30m hard cover+10m alluvial soil). ModelD: Models for extraction width of 4 pillars (84m) at a depth cover of 40m (20m hard cover+20m alluvial soil). The findings of the above different predictive models have been summarized in Table 4. 6. Modelling for estimation of appropriate face orientation and rib stability Orientation of the face should be oblique。 otherwise, when the face approaches the advance gallery, a thin long rib will be formed and a sudden collapse may take place. Such a collapse would expose a wide span in front of the powered supports throughout the face length instanteously. To overe this problem, obliquity of the face will minimise the exposed area and provide easier access to cross the advance gallery, from one end of the face to the other. With an oblique face crossing the advance gallery, triangular ribs will be formed and their stability is important during the shortwall mining. In order to estimate the safety factor of the pillar or triangular rib, its strength and the load on it must be determined. The strength of pillar/rib (S) is estimated using the CMRI pillar strength formula as given. 0 .2 7 1 1250 ec WHh h       MPa, (10) Where c is the uniaxial pressive strength of a 25mm cube coal sample (), H the depth of cover (50m), h the extraction height (), eW the (4A/Cp), (m), A the area of the rib and Cp the periphery of the triangular rib (m). Table 4 Findings of the predictive models Model no. Face advancement Condition of the different beds Main fall prediction ModelA 80m BedI, BedII and BedIII lying over the extracted area failed pletely, while BedIV is intact throughout the excavation span. Main fall reaching up to surface is not expected. 90m Due to further face advancement up to 90m for the excavation span of 104m wide face length, BedIV also fails partially and the fall may reach the surface. Main fall can be expected. 100m The overlying strata failure zone increases over the excavated area as the BedIV fails pletely. Main fall reached up to the surface. Conclusion: The strong BedII is expected to cave before 80m of face advance, while the main fall is expected to occur between 90 and 100m of face advancement. At the main fall, BedIV is expected to fail and subsidence will reach up to surface. ModelB 100m BedII overlying the extracted area failed pletely. Bed III caves in along with Bed II, while BedIV is intact throughout span. Minor weightings will be experienced at the face. 110m At the face advancement of 110 m, there will be partial caving of BedIV in the goaf but still overhanging over the span. Significant subsidence is not expected before 110m of face advance. 120m BedIV fails pletely and subsidence reached to the surface. Main fall reached up to the surface. Conclusion: It is concluded that for a face length of 84m with a depth of cover of 50m consisting of 30m hard cover and 20m weathered rock, the main fall is expected between 110 and 120m of the face advance. ModelC 130m BedI has caved before 130m of face advancement, while BedII is partially intact throughout the excavation span. Hence, the main fall reaching up to the surface is not expected. Main fall reaching up to the surface is not expected. 140m All the first three beds BedI, BedII and BedIII fail while BedIV fails partially. Main fall can be expected. 150m The overlying strata failure zone increases over the excavated area and the BedIV fails pletely. Subsidence will reach to the surface. Conclusion: For a face length of 84 m, cover depth of 40m consisting of 30m of hard cover and 10m of alluvial soil, the main fall is expected between 140m to 150m of face advance. ModelD 84m BedII fails pletely at this stage while BedIII caves partially in goaf along with BedII and minor weightings can be experienced at the face. Minor weightings can be expected at the face. 100m When the face advancement reaches up to100 m, BedIV fails partially and it remains overhang. Main fall can be expected. 110m The overlying strata failure zone increases over the excavated area as the BedIV fails pletely. Main fall reached up to the surface. Conclusion: For a face length of 84 m, cover depth of 40m consisting of 20m of hard cover and 20m of weathered rock/alluvial soil, the main fall is expected between 100m and 110m of face advance. The pillar load has been estimated using 3D BESOL software based on the displacement discontinuity method. During modelling, square elements of size 1m1m are employed and extraction of pillars and the advance gallery are formed by deactivation of elements. Based on the earlier experiences of bord and pillar depillaring caving panels, the norms for stability of pillars/ribs are given below: Factor of safety of pillars/ribs Stability Factor of safety≥2 Long term stability . pillars/ribs are not going to fail at all。 in other words, they may be treated as indestructible pillars. Factor of safety=1–2 Short term stability . it may fail within few years. Factor of safety≥ Stable for few days. The following input data were taken for the 3D BESOL modelling: Material Young’s Modulus Poisson’s ratio Rock 3Gpa Coal The in situ str。