Soft and loose ground is widely encountered in hydraulic engineering, civil engineering, mining engineering and so on. In treatment practices for this type of special ground, the general grouting materials used have a number of shortcomings, such as large consumption of materials and an unpredictable range of diffusion; it addition they are easily scoured by water. In this work a new grouting material was developed with pasty clay–cements to overcome the aforementioned problems with consideration of the specific structure and adverse environment of soft and loose ground. The rheological properties, setting times of the slurry and the mechanical characteristics of solidified grout stone were tested in a series of laboratory experiments. Compared with ordinary cement slurry and cement–clay slurry, the new material showed greater initial viscosity, adjustable thixotropy and setting time, a strong resistance to scour and a controllable diffusion range. An engineering application was analysed to illustrate that the new grouting material not only fulfils the requirements for grouting in soft and loose ground, but it can also be applied in soil layers with macrovoids as well as formations suffering from water soaking or scouring.

Tensile strength is an important soil parameter that affects the stability of structures built on clayey soils. This paper presents an experimental study of the change of tensile properties of red clay during wet-dry cycles. Cyclic wet-dry tests were performed on compacted red clay specimens with different initial water contents and dry densities. Direct tensile tests and Brazilian split tests were then conducted on these specimens to determine the soil strengths. The effects of initial water content, initial dry density, number of wet-dry cycles, and crack rate on the tensile properties of red clay were investigated. The results demonstrate that the tensile strength of red clay is generally 1.566 times the splitting strength. Both the tensile strength and splitting strength are negatively correlated with the initial water content but are positively correlated with the initial dry density. Because of the presence of desiccation cracks, the tensile strength goes on reducing under wet-dry cycles. The tensile strength can be expressed by a power function of the initial water content, initial dry density, and crack rate. The proposed equation is useful to evaluate the tensile strength of cracked soils subjected to wet-dry cycles.