DOI: 10.25442/hku.25922245.v1
title: <i>Supporting data for "Effect of Polymeric Microcapsules on Mechanical Behavior of Sands"</i>

description: Microcapsules have been demonstrated to self-heal cementitious materials by enhancing, switching and prolonging their physical properties in response to external stimuli. However, their potential application in granular materials are yet to be assessed. To prepare infrastructure for a changing climate, it is essential to develop adaptable, sustainable and autonomous solutions that is beneficial to the mechanical properties of soils, such as strength enhancement and deformation mitigation, when necessary. This thesis aims to facilitate the effective application of self-healing microcapsules by providing an insight into the effect of polymeric capsules on mechanical properties of sands. The specific objectives are to (1) investigate the microcapsules retention behavior in granular materials; (2) assess the effect of Tung oil on shear strength enhancement of silica sand; (3) encapsulate Tung oil, explore the controlled release mechanism, and investigate its applicability on shear strength enhancement of silica sand; (4) evaluate the effect of capsules on one-dimensional compression creep behavior of carbonate sand; (5) investigate the effect of capsules on drained triaxial creep behavior of carbonate sand with both global and local strain measurements.By adopting a constriction size-based model originally designed for filter, followed by conducting an extensive set of washout tests on microcapsule-gravel/sand mixture to monitor the loss of microcapsules in gravel/sand under flushing, a criterion for successful retention for microcapsules in granular materials was established, which considered the size change of microcapsules during wetting/drying and their adhesion nature.To address the second objective, the effect of Tung oil on mechanical behavior of saturated silica sand by means of drained/undrained triaxial compression tests was studied, concentrating on the isotropic compression, critical state, stress dilatancy and peak strength enhancement. SEM-EDS and TGA analyses were utilized to support the influence of bonding breakage and coating abrasion on the mechanical behavior of sand.Tung oil was enclosed in microcapsules for their use in sand. Some basic physical properties of sand-capsule composite such as specific gravity, global void ratio and Tung oil release were initially determined. The mechanical behavior and stabilization efficiency of sand-capsule composite under varying void ratios, capsule dosages and confining stress are investigated. A predictive model to explain the strength variations induced by capsules was established.The deformation characteristics incorporating immediate and creep deformation, along with elastic and plastic deformation of both carbonate sand and its capsule-based composite in one-dimensional compression creep tests were investigated. The effects of relative densities, particle size and vertical stress on deformations are discussed. Micro-CT analysis observed the trigger mechanism of capsules in sands.The last objective was met by exploring the drained triaxial creep behavior of fine carbonate sand and its capsule-based composite with extra local strain measurement. The global/local axial and volumetric creep strains of both materials are analyzed. The stress-strain behavior and volume change from creep test are compared with those from monotonic loading test, revealing the creep mechanisms of both materials.This research shed light on the effect of microcapsules on strength enhancement and deformation mitigation of sands, providing a basis for their applications in infrastructures.