## 2 Materials and Methods
### Mixture Proportion Optimization and Test Methods
#### 2.2.2 Sample Preparation and Test Methods  
The flow value was measured in accordance with ASTM D6103 [27]. The fresh soil-based CLSM was poured into an open-ended polyvinyl chloride (PVC) cylinder (75 mm in diameter, 150 mm in height). The cylinder was lifted vertically within 5 s, allowing the mixture to flow into a patty. The diameter of the resulting slurry patty was measured in two perpendicular directions using a vernier caliper, as shown in Figure 2. The fresh density was determined using a cylinder mold (50 mm in diameter, 100 mm in height) in triplicate. The specimens were cast in PVC molds (50 mm in diameter, 100 mm in height). To prevent leakage, cling film was applied to the bottom of the PVC molds. Upon introducing the cement to the excavated soil, the resulting mixture (labeled T1) quickly formed a floc, rendering it non-fluid. The T1 samples were compacted layer by layer in the PVC molds. After 24 h, all samples were demolded and covered with PVC plastic bags to prevent water exchange with the curing environment. Subsequently, they were placed in a curing box with a temperature of 20 \(\pm\) 1 \({}^{\circ}\)C and a relative humidity exceeding 95% until the desired curing time (7, 14, and 28 days) was achieved. Unconfined compressive strength tests were conducted using an electro-hydraulic servo universal testing machine (WDW-100Y), with a loading rate of 1.0 mm/min, adhering to the Chinese standard GB/T 50123-2019. The strength tests were conducted in triplicate, and the average was adopted. The strain corresponding to the peak strength in the stress-strain curve is denoted as the failure strain \(\epsilon_{\mathrm{f}}\). The deformation modulus \(E_{50}\) was calculated using Equation (1) [28]. \[E_{50}=\frac{2\sigma_{1/2}}{\epsilon_{\mathrm{f}}} \tag{1}\]  
where \(\sigma_{1/2}\) represents the stress corresponding to half of the failure strain obtained from the stress-strain curves, in kPa. The peak strain energy \(E_{\mathrm{u}}\) is defined as the area under the stress-strain curve up to the peak strength. X-ray diffraction (XRD) spectra of the dry excavation soil powder were obtained using the X-ray diffractometer (D8 Discover, Bruker Corporation, Germany; with Cu K\(\alpha\) radiation at 40 kV and 30 mA). This was conducted in the 10-80\({}^{\circ}\) 2\(\theta\) range, employing a scanning rate of 2\({}^{\circ}\)/min. After 7 days of curing, the samples underwent 12 h of vacuum saturation to ensure complete pore filling with water. Subsequently, free water on the surface of the saturated specimens was removed using a wet towel, and their weight and volume were sequentially measured. The soil-based CLSM samples were placed in the measurement area of the  
Figure 2: Flow consistency test. low-field nuclear magnetic resonance (NMR) instrument (PQ-001 of Suzhou Newmag Analytical Instrument Co., Ltd., Suzhou, China). The relaxation signal of the sample can be obtained through a Carr-Purcell-Meiboon-Gill (CPMG) NMR pulse sequence. The transverse relaxation time \(T_{2}\) distribution curve and porosity of the soil-based CLSM samples were obtained through the inversion analysis software built into the instrument. Surface-limited relaxation is a crucial factor in the transverse relaxation process of water within porous media [21]. The pore diameter \(D\) can be calculated using the transverse relaxation time \(T_{2}\) according to Equation (2) [29]:  
\[\frac{1}{T_{2}}=\rho_{2}\frac{S}{V}=\rho_{2}\frac{F_{S}}{D} \tag{2}\]  
where \(S\) is the pore area, in nm\({}^{2}\); \(V\) is the pore volume, in nm\({}^{3}\); and \(F_{S}\) is the pore shape factor, with values of 1, 2, and 3 corresponding to planar, cylindrical, and spherical shapes, respectively. \(\rho_{2}\) is the surface relaxivity, in nm/ms. Here, a cylindrical pore shape was considered. The surface relaxivity represents the relaxation strength of the liquid-solid surface and is difficult to measure accurately. As suggested by [PERSON] et al. [21], \(\rho_{2}\) is assumed to be 12 nm/ms for cement-based materials.