## 2 Experimental Design  
### Preparation of Test Samples and Determination of Physical Properties  
The sandstone samples used in this study were collected from the vicinity of the Leshan Giant Buddha, which is situated in the same stratigraphic formation as the associated Buddha niche rock. This rock formation is characterized by distinct layering and is devoid of any noticeable fractures or folds. This rock formation primarily consists of thick, distinct layers of blocky red sandstone from the Jurassic-Cretaceous Jiaguan Formation \(K_{2j}^{3}\)[20]. The limestone chosen for the restoration of the Mingzu Mausoleum status in Huai'an originates from Sishui County, Jining City, Shandong Province. The Paleozoic Cambrian limestone found in this area is a result of the wing of the anticlinal tectonic stress field. This geological process led to the formation of a low mountain and hilly terrain, primarily characterized by various geological structures. Through a comparative analysis of the physical properties, microstructure, and mineral composition of the rocks, it has been determined that the lithology of the two limestone samples from different regions is essentially identical. First, the proposed cutting position was demarcated on the rock surface, and then a laser cutting machine was used to cut the rock sample into 50 square cubes according to the marked line. The specimens were thoroughly washed with deionized water to remove any surface debris, ensuring the exclusion of samples displaying noticeable visual discrepancies. Figure 1 illustrates the surface morphology of the sandstone and limestone samples. Both types of rocks exhibit smooth and compact surface textures, along with a relatively uniform particle size distribution. DZT 0276-2015, the comprehensive standard of the geological and mining industries in the People's Republic of China, consists of 31 elements [21]. This standard encompasses various testing methods, including hardness testing, uniaxial compression testing, acoustic testing, and more. Following the guidelines outlined in this standard, the rocks were subjected to various tests to determine their physical properties. The dry mass, free water absorption, and vacuum saturation of the samples were measured using a precision balance (Hengshun: JA5003, Yuyao, China, with a resolution of 0.001 g). The method of calculating natural water absorption is shown in Formula (1):  
\[\omega=\frac{M_{wet}-M_{dry}}{M_{dry}}\times 100\%; \tag{1}\]  
where \(\omega\) represents the natural water absorption rate (%) of the rock sample, and \(M_{dry}\) and \(M_{wet}\) represent the drying quality and natural saturation quality of the rock sample, respectively, g.  
The calculation method of porosity is shown in Equation (2):  
\[\varphi=\frac{M_{sat}-M_{dry}}{M_{sat}-M_{w}}\times 100\%; \tag{2}\]  
where \(\varphi\) represents porosity, which refers to the ratio of total pore volume to the total sample volume, %; \(M_{sat}\) represents the mass after saturating the sample via a boiling water saturation method and wiping away the surface water of the sample, g; and \(M_{w}\) is the immersion mass measured after the saturated sample is immersed in water, g.  
By analyzing the collected data, important hydraulic properties such as the water absorption rate and porosity were calculated. These properties provide valuable insight  
Figure 1: Macroscopic characteristics of sandstone and limestone. (**a**) Macroscopic characteristics of sandstone samples; (**b**) macroscopic characteristics of limestone samples. into the behavior and characteristics of rocks. To assess the macroscopic properties of the rocks, non-metal ultrasonic testing equipment (Koncrete: NM-4B, Beijing, China), a [PERSON] hardness tester (Botech: BH200C, Guangzhou, China) and an electro-hydraulic universal testing machine (Kexin: CSS-WAW 1000 DL, Changchun, China, with a loading rate of 0.255 MPa/s) were utilized. Ultrasonic testing equipment was used to measure the wave velocity, providing information about the rocks' internal structures.