Seepage Piping Evolution Characteristics in Bimsoils -An Experimental Study

Abstract

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.

Optimization of Multiple Seepage Piping Parameters to Maximize the Critical Hydraulic Gradient in Bimsoils

“…This experimental setup was previously detailed described by Wang et al [12]. Figure 4 shows the layout of the piping test system includes the rigid specimen holder, the servo pressurized watersupply system, and the specimen chamber system.…”

“…The detailed dimensions and structure of the mental cap, and locations of the inlet and outlet valve are shown in Figure 5. The confining pressure system ( Figure 6) is composed of the Hoek cell, air pump, barometer, pneumatic connector, and pneumatic pipe [12].…”

“…Note: for soil matrix, the wet state corresponds to natural state, and for rock block, the wet state corresponds to saturation state. In this work, dynamic compaction was used for the preparation of the bimsoils pecimens [10][11][12]26,27].The appropriate optimal hammer count was determined according to the relationship between the hammer count and the soil matrix density Compaction was done in a split mould by applying a dynamic pressure, using a compaction test apparatus. Owing to the high difference of elastic modulus between soil matrix and rock block, compactness of bimsoil is actual the compactness of soil matrix.…”

“…(a) Grain size distribution using sieving method for the used soil matrix; (b-d) Gravel, pebble and round rock blocks used in bimsoil specimen preparation, size range from 2 to 5 mm according to BS1377-1 (1990). In this work, dynamic compaction was used for the preparation of the bimsoils pecimens [10][11][12]26,27]. The appropriate optimal hammer count was determined according to the relationship between the hammer count and the soil matrix density Compaction was done in a split mould by applying a dynamic pressure, using a compaction test apparatus.…”

“…Many engineering geological disasters have direct relations to the bimsoils [3][4][5][6][7][8]. As is known, piping is a very common and severe kind of seepage failure, it has been pointed out that piping is considered as the main mechanism leading to the failure of hydraulic structures in bimsoils [12][13][14]. It is also the primary reason resulting in the instability of landslides, dam foundation, and dyke building, which are generaaly composed of bimsoils.…”