Effect of large void formation on strength of cemented glass beads

Gas hydrate dissociation can generate large amounts of gas and water in gas hydrate bearing sediments, which may eventually escape from the soil skeleton and form local voids within the sediments. The loss of fine particles between coarse particles or collapse of cementation due to wetting during heavy or continuous rainfall may form large voids within the soil structure. In this study, the effect of local void formation arising from gas hydrate dissociation, loss of fine particles, or dissolution of vanishing materials is examined in terms of the unconfined compressive strength. Glass beads, cement, and water are mixed and compacted into a cylindrical specimen with five equal layers to simulate the base soil structure. Empty capsules used for medication are embedded in the middle of five equal layers to mimic relatively large voids that are disconnected and permanent. A series of unconfined compression tests was performed on capsule-embedded cemented glass beads by varying the number and direction of capsules in each layer. The unconfined compressive strength of cemented glass beads with capsules decreased up to 35% compared to the case without capsules due to increasing void formation, which depends on the quantity and direction of the embedded capsules. The results of this study can be used to predict the reduction in the strength of soils due to locally disconnected large voids.

► Void formation can reduce the strength and the strength decreases as the total volume of the formed voids increases.
► The volume and direction of the formed voids can contribute to variation in the strength.
► The volume of voids is more important than either the direction or length of voids.
► The volume of voids is the most important factor with regard to the strength of a specimen with large isolated voids.