## 4 Methods
### Site Suitability Evaluation Based on Multi-Factors  
We can quantify the required engineering adaptability, as characterized by RI structural matching. Ideally, we identify areas that can be built and reinforced efficiently with stable rock masses that are minimally disturbed by problematic geological bodies. The timely reinforcement countermeasure test [39] steers our analysis away from areas with a high likelihood of irreversible deformation and failure, which is vital in the planning and construction of large scientific installations. By combining the data from the geological surveys, digital drilling analyses, geological structural modeling, and problematic geological body mapping, as well as engineering testing, we created a scaled 3D model of CSNS that demonstrates how the engineering structural layout is affected by changes in geological conditions [40; 41] such as weathering and rock mass integrity. The rock mass integrity was classified based on Rock Quality Designation (RQD) and Rock Core Index (RCI). RQD is measured in percentage from the core samples of a borehole, in which the combination of core pieces of solid rock over 10 cm (4 in.) is divided by the core run length. Thus, RQD is actually a measure of the percentage of the solid rock mass. In addition to calculating the \(RQD\) values for the rock masses in samples from the drilled cores, we also employed the Rock Core Index (\(RCI\)) as a way to describe the integrity of the cored samples [42]. The \(RCI\) defines the continuity of the core sample (and the rock mass it sampled):  
\[RCI=1\times Cr_{1}+3\times Cr_{3}+10\times Cr_{10}+30\times Cr_{30}+50\times Cr _{50}+100\times Cr_{100} \tag{1}\]  
where \(Cr\) is the core acquisition rate for different drilled core lengths [31]. \(Cr_{1}\), \(Cr_{3}\), \(Cr_{10}\), \(Cr_{30}\), \(Cr_{50}\), and \(Cr_{100}\) represent the proportion of the core sections with lengths that fall into intervals of 1-3 cm, 3-10 cm, 10-30 cm, 30-50 cm, 50-100 cm, and greater than 100 cm, respectively. For example, if the total core length is 250 cm, and 100 cm of that core is in sections with lengths that fall in the 10-30 cm interval, and the remaining 150 cm of the core has lengths that are greater than 100 cm (i.e., the remaining 150 cm of the core is completely intact), then \(Cr_{30}\) is 0.4 and \(Cr_{100}\) is 0.6, and the final, \(RCI\) value is 72. The numerical constants in the \(RCI\) equation are effectively weights so that cores with longer intact sections will have higher \(RCI\) values. We also tested the water sensitivity and dynamic disturbance response of some problematic geological bodies (e.g., fault gouges, weathered rocks, etc.) at the CSNS site; both characteristics can greatly affect the site stability, the construction quality control measures, and the engineering reinforcement implementation. Each of these analyses represents a single factor in the calculation of the Engineering Geological Suitability Index (\(EGSI\)):  
\[EGSI=\sum wifi(x,\,y) \tag{2}\]  
where \(w_{i}\) is the weight ratio of influential factors, \(f_{i}(x,y)\) is the normalized single factor influential function value, which ranges from 0 to 1, and each factor is evaluated at geographical coordinates \((x,y)\). In plane map models, an \(EGSI\) value can represent the individual \(EGSI\) values at a constant \((x,y)\) and sum over varying depths. \(EGSI\) takes its role as one important parameter for quantifying rock mass quality in the Hoek-Brown criterion [43]. The \(EGSI\) chart is based on qualitative geological observations regarding the degree of fracturing and surface condition of joints. The software GOCAD (Geological Object Computer-Aided Design) Version 2011 provides a powerful geostatistical analysis module. GOCAD is a registered trademark (GOCAD (TM) (Mira Geoscience Ltd., Montreal, QC, Canada) [44; 45]. It uses the measured data as the attribute volume, assigns each point in 3D space, and then carries out appropriate interpolation for the establishment of 3D attribute volume to assist in the 3D visual query [46].