Abstract: The roadways excavated in expansive and weak-cemented soft rocks in Shajihai coal mine have caused serious large deformation problems such as roof failing, side collapse and floor heave in the field. In this paper the X-ray diffraction, SEM scanning, mechanical tests and water absorption tests have been performed to study the characteristics of this soft rock and mechanism of deformation and failure of roadway based on the actual site situation. Research on deformation mechanisms have shown that the main reasons for roadway failure is that the surrounding rocks are with features of weak-cemented and strong swelling ability. When exposed to severe excavation disturbance and low strength support, the surrounding rock cannot match the deformation of the support system by traditional anchor-bolt-mesh support, and the capacity of surrounding rock is wasted in roadway supporting system. Based on the above, the support capacity of surrounding rock has been employed for energy absorbing and ground pressure decreasing, and water isolation for reinforcement has also been performed. Based on the theory of absorbing energy support using Constant Resistance and Large Deformation (CRLD) bolts and anchors, a new support scheme has been put forward, which is the CRLD bolt + mesh + sprayed concrete layer + CRLD anchor + bottom anchor pipe. Field monitoring results have shown that the large deformation of weak-cemented soft rock has been better controlled than before by the application of new support scheme.

Key words: weak-cemented soft rock, expansive characteristic, constant resistance and large deformation bolts, large deformation control, numerical analysis