Influence of Boundary Conditions on Cracking of Sanxingdui Moon Bay City Wall

Abstract

The Sanxingdui Moon Bay City Wall, in China, is built of pale-yellow sand and yellow-brown clay, and the yellow-brown layers are suffering severely. In order to discuss the desiccation cracks in a section of this wall, this paper conducts evaporation tests in laboratory and observes the variations in the characteristics of the boundary conditions of the bottom surface of the sample. The results show that the boundary conditions of the bottom surface of the sample consist of two free boundaries, two sliding boundaries, and one fixed boundary from the outside to the inside. During the drying process, the free boundary extends, but the fixed boundary shrinks; the sliding boundary also remains basically stable. We obtain the surface tensile stress distribution under different boundary conditions through stress analysis and deduce that the tensile stress distribution has a trapezoidal pattern. Moreover, we calculate the lower limit on the crack spacing of the sample using the energy method, and the double of the sum of the maximum sliding boundary length and the free boundary length is the upper limit to the crack spacing. Maintaining the stability of the soil moisture content of the site is the main factor in the protection of the earthen archaeological site under the humid conditions of the museum above the site. In order to reduce the water evaporation rate of the soil, the surface of the site should be coated by a protectant, the main determining features of which are permeability, tensile strength, and compatibility with the earthen site.

Study on the evolution process of drying-wetting cycle cracks in compacted loess based on DIC technology

“…The strain and displacement fields in the whole process of soil shrinkage and cracking are studied based on digital correlation technology [12] [13]. Through image processing and digital image correlation techniques, the changes in tracer point displacement and strain field during soil shrinkage and cracking are obtained [14] [15]. At present, DIC technology is rarely reported in the field of research on cracks in the dryingwetting cycle of loess.…”