Joint is the main factor influencing elastic modulus of rock mass. According to the statistics of joints parameters

a constitutive relation of jointed rock mass is deduced by combining with strain energy

which can reflect the weakening and anisotropy of elastic modulus. Then

the characteristics and influencing factors of elastic modulus of jointed rock mass are analyzed by using tunnel surrounding rock of Ji-Tu-Hui railway as an example. The results show that the weakening and anisotropy degree of elastic modulus vary with the angle between stress and structural plane normal

which can obtain the maximum value at the angle of 54.5°. Meanwhile

the weakening degree of elastic modulus is in negative correlation with the friction angle and cohesion of joints

but in positive correlation with the mean radius and density of joints. And when the mean radius is over 3 m

the elastic modulus tends to be stable. Confining pressure also has influences on the elastic modulus of rock mass. When confining pressure is increased

the value of elastic modulus increases

and weakening and anisotropy degree is decreased. When the confining pressure reaches 2.32 MPa

the weakening and anisotropy will disappear.