Abstract
Piping is a kind of seepage failure mode that commonly occurs under the influence of seepage force in soil materials. Many studies have been done to study the characteristics of piping for soil materials, however, the initiation and development mechanism of piping in bimsoils is poorly understood. In this work, an experimental program was set for investigating the evolution process of piping, in a self-developed servo-controlled flow–erosion–stress coupled testing system. All the studied samples with rock block percentage (RBP) of 30%, 40%, 50%, 60%, and 70%, were produced as a cylindrical shape(50 mm diameter and 100 mm height) by compaction tests with different hammer strike counts to roughly insure the same void ratio. The results show that the amount of rock blocks in bimsoil samples significantly influenced the initiation and development of piping. Furthermore, the stress state has a crucial influence on the critical hydraulic gradient, seepage velocity, permeability, erosion, and migration of soil particles. Moreover, interactions among soil matrix, rock blocks, and rock–soil interfaces control the seepage stability of the bimsoil sample.
Highlights
The term bimsoils is used to describe structurally complex geological formations characterized by a fine-grained soil matrix which includes in a typical block-in-matrix fabric, rock block fragments of variable sizes, strength, and different lithologies [1]
After the fine soil particles clog the pores during movement, bimsoil sample
Piping seepage failure includes a series of complex movement behaviors, such as the erosion, migration of fine soil particles →contact erosion of rock–soil interface→ forming of pore channels→ blocking of flow channel by fine soil particles→ breakdown of the blocked flow channel →re-blocking of the flow channel, etc
Summary
The term bimsoils (block-in-matrix-soils) is used to describe structurally complex geological formations characterized by a fine-grained soil matrix which includes in a typical block-in-matrix fabric, rock block fragments of variable sizes, strength, and different lithologies [1]. These complex mixtures are widespread and originate by several geological processes. Due to the different properties of the soil matrix, the types of seepage failure include erosion, flowing soil, and piping. High seepage pressures may remove soil material to such an extent that geotechnical structures may, and do, collapse
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