Abstract: To provide support for reasonable design of the underground structure lining, random pore models which contain triangle, quadrangle and circular pore shapes respectively have been adopted to study the relationships between horizontal lateral pressure coefficient of porous rock and porosity, pore shape and pore pressure in numerical method. According to whether the contact surface between the rock and the lining has been handled or not, the models are simplified into two kinds, lateral boundary with porosity and without porosity. The main results are as follows：1) Horizontal lateral pressure coefficient decreases linearly with porosity in models without pore pressure, and when porosities are the same, the lateral pressure coefficient decreases with L/A of pores(L means length of the side of pore and A means area). 2) When the pore pressure takes effect on the models, the lateral pressure coefficient increases with pore pressure in both models. The larger the porosity, the more significant change of lateral pressure coefficient will be. 3) When porosity, pore shape and pore pressure of the models are the same. The lateral pressure coefficient is greater in the second kind of model whose lateral boundary contains more pores than the first kind of model. 4) Lateral pressure coefficient increases with L/A of pores when porosity and pore pressure are the same.

Key words: porosity, pore pressure, pore shape, lateral pressure coefficient