## 1 Introduction  
The western region of China is rich in coal resources, which is the key development region of the country in the next 30-40 years. The main mining coal seam in this region is mainly distributed in 30-500 m. However, with the increasing depletion of shallow coal resources, the mining depth of coal resources in the western mining area is also increasing. Currently, there are many high gas mines in the western part of China, such as Wuhushan Coal Mine and Huangbaicil Coal Mine in Wuhai Mining area of Inner Mongolia. With the increase in mining depth, the surrounding rock stress and gas pressure of coal mine will further increase, and coal and gas outbursts will become one of the main disasters threatening these mining areas [1]. The mechanical properties of coal and rock mass containing gas are important factors affecting the outburst of coal and gas. In view of the characteristics of deformation and mechanical response of gas-containing coal, scholars at home and abroad have conductedsubstantial research and obtained certain research results. For example, [PERSON] [2], [PERSON] [3], [PERSON] [4], [PERSON] [5], [PERSON] [6], and other scholars from Chongqing University [7; 8; 9; 10], Henan Polytechnic University [11], China University of Mining and Technology [12; 13], Northeastern University [14; 15], Anhui University of Science and Technology [16], Qingdao University of Technology [17], China Coal Technology & Engineering Group [18], and other Chinese universities and research institutes carried out mechanical tests and CT scanning tests of gas-containing coal under different loading and unloading confined pressures and unloading axial pressure conditions using a conventional triaxial testing machine or true triaxial testing machine to study the factors affecting the mechanical properties of gas-containing coal. Scholars have also studied the deformation and failure characteristics of gas-containing coal and its constitutive model based on the catastrophe theory [19], chaotic object theory [20], elastic constitutive model of porous media [21; 22], double media theory [23], coupled percolation, the splitting and damage model of rock fracture [24], creep model [25], Biot-type constitutive equation [26], HJC constitutive model [27], deformation and failure characteristics of gas-containing coal and its constitutive model. Some scholars further revealed the deformation and fracture laws of gas-containing coal and rock mass using numerical simulation methods and software such as the particle method [28], three-dimensional discrete fracture network modeling [29; 30; 31], remote sensing imagery [32], damage finite element Calculation program [33], COMSOL Multiphysics [34], and RFPA [35; 36], et al. However, previous studies often combined several factors to comprehensively study the mechanism of coal and gas outbursts. There are relatively few in-depth research results on the mechanical properties and failure laws of gas-containing coal samples under different gas pressure conditions. There are also few research results on the mechanical characteristics of gas-containing coal in Wuhai mine area of Inner Mongolia. In this paper, the method of theoretical analysis, experimental testing and numerical simulation are combined used. Taking the gas-bearing coal seam in Wuhai Mining area of Inner Mongolia of China as the test base, the influence of different gas pressure on the mechanical characteristics of coal and rock mass containing gas and its deformation and fracture rule are analyzed emphatically The research results have important theoretical significance and practical value for the prevention and control of coal and gas outburst accidents in Wuhai mining area and the drainage of coal seam gas under the influence of mining. The test gas-containing coal samples in this paper were taken from the raw coal of No.9 coal seam of Wuhushan Coal Mine of Wuhai Mining area of China.