## 1 Introduction  
In China, marine silt is widely distributed in coastal areas, and its physical and engineering properties are close to those of soft clay. It is difficult to use in engineering due to characteristics such as high water content, high compressibility, low shear strength, and high sensitivity. Therefore, marine silt must be treated to meet engineering needs [1]. Since marine silt contains humus and many kinds of ions, it is frequently added to cement and other curing agents for treatment [2, 3]. In situ solidification technology can quickly form an artificial hard crust of a certain strength and thickness on the surface of soft soil by adding a curing agent to in situ soft soil and stirring it evenly [4]. Currently, in situ solidification mostly adopts a single and equal thickness solidification method, which is inflexible, for soft foundation treatment. Meanwhile, its bearing capacity may be much higher compared to the actual needs, resulting in a waste of resources. On the basis of in situ solidification, the gridded hard crust with different thicknesses is formed considering that the project should solidify the soil with different depths according to local conditions (Figure 1). Then, it is utilized to lower the project cost, presenting a good application prospect. Therefore, it is of great significance to investigate the destruction mode and influence factors of the gridded hard crust for its popularization and application. Gridded hard crust is mainly used for shallow in situ curing, where the loads are transferred to the bottom bearing layer. This type of hard-shell layer is known as a gridded hard crust because of the gridded structure it forms after construction and depending on the shape the structure is divided into two parts: the hard crust and the grid structure. The addition of this special structure to a soil that is inherently multi-phase and complex makes the interaction between them extremely complex and the deformation and damage limit states are highly uncertain. Physical simulation test technology takes the similarity principle as a basis. Through the establishment of an effective physical model, the prototype has been deeply studied, has been widely used in many fields of geotechnical engineering, and has become one of the important means of scientific research and technical problem-solving. However, the internal deformation law of soil for traditionally common similar materials cannot be directly observed as its interior is invisible. Transparent soil material is a kind of transparent material similar to soil. This is a general name for synthetic transparent simulation materials with natural soil engineering properties. They are composed of aggregate and pore fluid with the same or similar refractive indices. Owing to the similar refractive indices of aggregate and pore fluid, there is no significant refraction or scattering when light passes through transparent soil. Hence, this kind of \"soil\" is transparent, and the appearance of similar materials of transparent soil makes it possible to \"directly observe\" the internal deformation of the model [5,6]. At present, it has been widely adopted in foundation engineering, tunnel engineering, foundation pit engineering, slope engineering, and other related scientific and technological fields [7, 8, 9, 10, 11]. On the basis of verifying that transparent clay can be applied to the experimental study of shield tunnel excavation face instability, [PERSON] [12] analyzed the evolution process of excavation face instability under different buried depth ratios from the perspective of soil movement and studied the characteristics of instability stages, zoning, and morphology, as well as the change law of surface settlement. With transparent sand and PIV technology, [PERSON] [13] performed a series of centrifugal model tests on anchor piles under the oblique uplift load and explored the relationship between the soil displacement field and pile foundation bearing capacity.