Advances in Civil Engineeringon the soil surface has a triangular pattern, and the maxi mum tensile stress is located in the middle of the soil laver 11]. According to the strength criterion, an expression fo the crack spacing can be obtained [12]. However, when the ratio of the soil laver thickness to the frictional force of th contact surface is small, the contact surface is suppressed, and the equation proposed by Price [12] is unable to predict the crack spacing [131. Therefore, it is necessary to consider the variation of the shear stress along the thickness. Cox [14 used a two-dimensional model to analvze the tensile stress listribution when the soil-substrate contact surface is fixed. Through the numerical analysis, Peron et al. [15] found tha the tensile stress on the top surface of the soil layer is evenly distributed and then calculated crack spacing according to the energy balance method. Ji chao et al. [16] proposed a crack spacing formula under fixed boundary conditions b analyzing the stress state of unsaturated soils and using th tensile strength criterion. Costa et al. [17] employed the tensile strength criterion and the energy balance method to analyze the crack spacing, and the energy balance metho attained the minimum crack spacingMany investigators have researched the factors influ- encing cracking through lab-scale experimental examina tion, theoretical analysis, and numerical simulation. A higher temperature, a lower soil density, a greater so thickness, and a higher friction of the contact surface will all ause a larger average crack area [18, 191. The ratio of the crack spacing to the thickness decreases by an increase in th soil thickness and variations in the mechanical properties of the soil [20]. However, the studies on cracking mechanism are based on a single boundary condition, and the influence of the variations in the boundary conditions on the crack spacing is not considered. Therefore, it is necessary to in- vestigate the impact of the variations in the boundary conditions on the crack spacing.In this work, a section of the Sanxingdui Moon Bay City Wall is discussed. A drying experiment is conducted, and the image of the displacement field of the cracking process is acquired by image processing and digital image correlation technology. By analyzing the shrinkage process of the sample, the variations in the characteristics of boundar conditions are obtained. Furthermore, the stress distribution under different boundary conditions is derived by stress analysis, and the variation of the crack spacing is further analyzed.