Numerical Analyses on Deformation and Failure Characteristics of Surrounding Rock of Gob-Side Entry Retention by Roof Cutting

Table 3

Parameter calibration process of block and joint.

Progress	Item	Explain
1	Deformation parameter of block and tensile strength of block	The block deformation parameters including the elastic modulus and Poisson’ s ratio were set to values of the intact rock parameters, and the tensile strength was set to 1/20 of the compressive strength of the intact rock (it is generally considered that the tensile strength of rock mass is 1/50–1/10 of the compressive strength).
2	Deformation parameter of joint	Using the equations provided in the UDEC user manual, the range of normal stiffness kn and tangential stiffness kn of the joints was obtained (Itasca Consulting Group Inc, 2002). The secant modulus obtained from the numerical uniaxial test was made approximately equal to the elastic modulus of rock masses by setting kn/ks = 1. Poisson’s ratio obtained from the numerical uniaxial test was made approximately equal to oisson’s ratio of rock masses by changing kn/ks ratio. The values of kn and ks were finely adjusted once more to make the elastic modulus and Poisson’s ratio satisfy the above conditions at the same time.
3	Internal friction angle and cohesive of block and joint	The uniaxial compressive strength resulted from the numerical uniaxial test was made approximately equal to the uniaxial compressive strength of rock masses by changing the internal friction angle and cohesion of the blocks and joints.
4	Tensile strength of joint	The tensile strength resulted from the Brazilian splitting test approximately equals to the tensile strength of rock masses by varying the value of the tensile strength of the joint.