Ground Characteristic Curve and Convergence Confinement Method - A case study

Abstract

Ground Characteristic Curve (GCC) describes the relationship between the initial stress of rock mass and the displacement of rock mass on the boundary of tunnels. Another way that indicates the relationship of support pressure and the level of Convergence Confinement of tunnels by percent. The using GCC to design supports in the underground construction has many advantages to ensure full utilization of the loading bearing capacity of rock mass, and release a part of initial stress in the rock mass around tunnels. However, this method is limited in the field of underground mines in Viet Nam. This article analyzed and applied GCC and Convergence Confinement Method (CCM) to design the supports of underground constructions and applied them to the geological conditions of the Nam Mau coal mine - Vinacomin. The research results show that at the geological conditions of the drift at level +125 in Nam Mau coal mine, TH section steel ribs with flange width 124 mm, section depth 108 mm, weight 21 kg/m, maximum support pressure 1.98 MPa, and spacing 700 mm were applied. Results of research in this method can be applied to design rock supports for deep roadways and other drifts in the underground mines in Quang Ninh province of Viet Nam. By a factor of safety, mobilized support pressure, wall displacement of roadways, and convergence of roadways the designation and selection of rock support around roadways will become clearer. Near future this method should be widely applied in the combined protection design in deep roadways in underground mines in Viet Nam. Although the method has great advantages, it is still necessary to have complete and detailed monitoring data of the geological and hydrogeological conditions in the area under consideration.