## 1 Introduction
calculated and regressed the relational expression between resistivity and damage variable of coal mass by using the joint test method of uniaxial compression and AE parameters, which verified the feasibility of its variation regularities [17]. [PERSON] et al. conducted Brazilian Split tests for limestone samples that further corrected the variable of resistivity and AE characteristics, which obtained the response regularities of resistivity and AE parameters in different bedding directions and discovered evolution regularities of damage variables [18]. Recently, it was found that the resistivity of coal mass is affected by temperature, frequency, applied electric field and its properties. [PERSON] et al. conducted studies on and discovered the resistivity variation regularity decreased linearly at temperatures above 45 \({}^{\circ}\)C for raw coal, while the resistivity of briquettes showed a linear decline in the temperature range of 15b \({}^{\circ}\)C\(\sim\)65 \({}^{\circ}\)C [19]. [PERSON] et al. carried out a series of experiments on fly ash and found that resistivity increased at first and then gets worse with the increase of temperature, and discovered there is peaking in the range of 373-473 K [20]. [PERSON] et al. pointed out that resistivity decreased exponentially with increase in test frequency, and appeared different characteristics in different test directions [21]. In summary, most of researches on damage evolution regularity and resistivity variation regularity had been carried out independently, or more reflected the inherent relation between the two by data fitting, and it was not took into account inherent relation between resistivity and damage evolution of coal-rock mass. And that the majority of researches had been carried out under uniaxial compression conditions, and the coal and rock mass were usually under constant load loading conditions before the disaster, so that the complex stress environment of the actual coal and rock mass was not adequately considered [22]. Besides, the electrical resistivity is more susceptible to temperature, frequency, applied electric field and its properties, and the change of loading environment can easily cause abrupt change of resistivity, so that it will affect the instantaneous determination of damage of coal-rock mass. But acoustic emission is an intrinsic property during deformation and failure process of coal-rock mass, and it has strong sensitivity to the deformation and failure, which can determine the time of failure of the coal-rock mass exactly. And AE parameters have strong scale effects on the process of coal sample damage, which can cause not only in terms of specimen peak stress changes with the different size and slenderness, but also in terms of AE signals cumulative counting changes significantly [23]. To this end, it is important to adopt the simultaneous test method of resistivity and acoustic emission to establish the relationship between the AE damage variable and resistivity of coal mass under multi-stage loading without considering the scale effects in this paper, and calculate the resistivity by using cumulative AE ringing count, so as to provide a basis for the application of resistivity and AE monitoring and forecasting technology, and further improve theoretical basis of electric prospecting technology for predicting coal-rock dynamic disasters.