The integrity coefficient K_v of bed rock is one of the important approaches to evaluate the stability of engineering rock mass, but this parameter is difficult in frequent field tests. The integrity coefficient is the quantitative index for evaluating the complete deformation of rock mass, while the damage variable represents the level of damage of the jointed rock mass, and both have similar physical meanings and represent the degree of deterioration of surrounding rock. Damage variables and damage constitutive models were constructed based on Weibull distribution damage model and Synthetic Rock Mass (SRM) model. The relationship between damage variables and numerical calculation and damage constitutive curves of different weathered granite rocks in Hongtuzhang tunnel was calculated. A new method for evaluating integrity coefficient of rock mass is proposed.

Ground penetrating radar (GPR) is widely used in advanced geological prediction. It is necessary to choose a scientific and effective evaluation method to give a reasonable evaluation of the accuracy of prediction. In this paper, a method based on improved analytic hierarchy process (AHP) and GPR is proposed to evaluate the accuracy of advanced geological prediction. Based on the analysis and induction of the factors that affect the accuracy of GPR prediction, an improved AHP is proposed, in which a new measure of "numerical weight" is added and the principle of maximum membership degree is integrated, and an improved AHP model is established for GPR prediction accuracy classification and evaluation. The engineering application of Xiaobeishan Tunnel of Jie-Hui Highway is taken as a case study, and it is proved that the evaluation indices are easy to obtain and the evaluation results are accurate and reliable. The improved AHP-GPR method can be further used for other tunnel engineering.

In underground engineering such as tunnel engineering, the condition of surrounding rock such as water-containing jointed rock mass is a common engineering geology. For broken, water-containing surrounding rock, the reasonable measures to prevent and drain water has always been a key issue. Based on the statistical information of the structural surface of the surrounding rock of the Hongtuzhang tunnel, DIPS software was used to classify the structural plane of the tunnel. Based on the statistical analysis of the occurrence, size, and density of the structural plane, the two-dimensional structural plane network model of the rock mass was established, and the permeability tensor (K₁ = 1.61 × 10⁻⁶ m/s, K₂ = 5.78 × 10⁻⁷ m/s) was calculated. Consider the worst orientation, the permeability tensor (K₁ = 1.61 × 10⁻⁶ m/s) was selected to calculate the grouting design. Based on the theory of limited discharge, the influence of parameters of permeability coefficient ratio n and thickness of grouting layer T_g on the tunnel water inflow and lining external water pressure was analyzed. The recommended value of tunnel drainage was 3.0 m³/m∙d, then the corresponding grouting circle parameters were put forward (permeability coefficient ratio n = 100, thickness of grouting layer T_g = 8 m).

In this study, grading of surrounding rock was based on rock mass basic quality (BQ) values according to the specifications in China. Numerical approach was to construct synthetic rock mass (SRM) model to represent the jointed rock mass, and obtain the strength of the rock mass. It represented intact rock by the bonded particle model (BPM), and represent joint behaviour by the smooth joint model (SJM) to construct the discrete fracture network (DFN). In the Hongtuzhang Tunnel, the micro properties of granite cores with different weathered degrees were determined by the validation process, and the calculation representative elementary volume (REV) of surrounding rock was 15 m×15 m. Five slightly weathered, three slightly to moderately weathered, and two moderately weathered granite surrounding rock mass models were established based on the probability distribution of joint sets in each borehole, the conversion BQ value was acquired according by the calculated strength of rock mass model. It was discussed the differences of surrounding rock grades between the geological survey method and the numerical calculation method, and then found that the geological survey report is higher than the numerical calculation method predicted. And the numerical calculation is consistent with the actual excavation of rock mass at borehole A1388.