# Natural Creation of Large Rock Cavern: Can We Construct Them? Jenolan Caves as a Case Study
## 3 Extended Investigation for a Man-Made Rock Opening to Same Size of the Grand Arch
### Deformation Assessment of Man-Made Rock Opening to Same Size of Grand Arch  
In this part of the investigation, a man-made rock cavern with an arched roof, vertical wall, and flat invert is formed with same span and height to the Grand Arch, i.e., 55 m in span and 24 m in height. Figure 9 illustrates the shape of the overlaying opening to the Grand Arch for easy reference. Model M3's geological conditions are adopted, while four models are created, namely Models MM-1 to MM-4, as shown in Figure 10a-d, respectively. Other parameters adopted for these four models are summarized in Table 3. For the detailed input parameters of Model M3, refer to Table 1.  
Figure 10: _Cont._  
Figure 9: A man-made rock cavern to be formed to be the same size (span and height) as the Grand Arch. (Note: Green line is the shape of man-made rock cavern, and black line is the shape of Grand Arch). These four models of opening, including unsupported and pattern bolts-supported, were created to examine engineering responses at the periphery of deformation and stress alternations on the ground. Models MM-1 and MM-2 were created with different arch shapes, with a ratio of arch rise to span of 0.2 and 0.3, respectively. Models MM-3 and MM-4 are in same shape as Models MM-1 and MM-2, respectively, but these two models were installed with pattern rockbolts. The purpose of Models MM-3 and MM-4 is to check the function of rock reinforcement as a stabilization measure for the opening and to compare with those with unsupported conditions for their opening. \begin{table}
\begin{tabular}{p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt} p{28.5 pt}} \hline \hline
**Model 1** & **Arch Roof Shape** & **Pattern Bolts Support** & **Remarks** & **Model Roof and Wall Deformation (mm)** & **RSR\% and WCR\%** \\ \hline MM-1 (Figure 10a) & \(\bullet\) & Elliptical Rise-to-span ratio = 0.2 & No & (Unsupported rock opening) & 46 and 13 & 0.084\% and 0.047\% \\ MM-2 (Figure 10b) & \(\bullet\) & Elliptical Rise-to-span ratio = 0.3 & No & (Unsupported rock opening) & 25 and 10 & 0.045\% and 0.036\% \\ MM-3 (Figure 10c) & \(\bullet\) & Elliptical Rise-to-span ratio = 0.2 & Yes & Rockbolt length, 10.25 m, \(\varnothing\)28 mm 2 & 32 and 11 & 0.058\% and 0.04\% \\ MM-4 (Figure 10d) & \(\bullet\) & Elliptical Rise-to-span ratio = 0.3 & Yes & As \(\mathrm{SI}=55\) (or Q = 4), calculated rock support pressure = 103 kPa 3 & \(\bullet\) & \(\bullet\) & \(\bullet\) & \(\bullet\) \\ \hline MM-4 (Figure 10d) & \(\bullet\) & Elliptical Rise-to-span ratio = 0.3 & Yes & Calculated rockbolt spacing, 1.39 m 4 & 20 and 8 & 0.036\% and 0.029\% \\ \hline \hline \end{tabular}  
* Model setup, geological conditions, rock mass parameters, and an invert level of cavern are the same as Model M3 (see Table 1). 2 Q-bolt length equation is adopted, where B = 55 m and ESR equals to 1 are assumed. 3 Rock support pressure is estimated based on Q-system [47], where \(\mathrm{In}=6\), \(\mathrm{Jr}=1\), and Q = 4 are assumed. 4 Bolt spacing equals to square roof of \({}^{\prime}\) bolt capacity divided by rock support pressure\({}^{\prime}\).  
\end{table} 
Table 3: Details of man-made rock-cavern models for RS2. Figure 10: Modeled deformation results of the man-made rock caverns. (**a**) Model MM-1: UCS of rock = 35 MPa; joint spacing = 2 m; unsupported; roof arch’s rise-to-span ratio = 0.2; in situ stress ratio (k) = 2.76. (**b**) Model MM-2: UCS of rock = 35 MPa; joint spacing = 2 m; unsupported; roof arch’s rise-to-span ratio = 0.3; in situ stress ratio (k) = 2.76. (**c**) Model MM-3: UCS of Rock = 35 MPa; joint spacing = 2 m; bolted pattern; roof arch’s rise-to-span ratio = 0.2; in situ stress ratio (k) = 2.76. (**d**) Model MM-4: UCS of rock = 35 MPa; joint spacing = 2 m; bolted pattern; roof arch’s rise-to-span ratio = 0.3; in situ stress ratio (k) = 2.76. Note for colours: Red is a maximum deformation, and Blue is the minimum deformation in media. The modeled deformation of these four models (MM-1 to MM-4) is summarized in Table 3 and presented in Figure 10a-d.