Among soil improvement techniques used to increase strength of loose and
medium-dense sand deposits are the dynamic means, such as vibrocompaction and blasting. Sands often exhibit a drop in cone penetration resistance immediately after the disturbance, but a gradual increase in the resistance occurs in a matter of weeks and months. An
explanation of the former is sought in the analysis of the stress state immediately after the dynamic disturbance, and a justification for the latter is found in the process of stress corrosion cracking (or static fatigue) of the micro-morphologic features at the contacts between sand grains. Some experimental evidence is demonstrated for fracturing of the microscopic features on the sand contact surfaces. Discrete element method calculations are carried out to strengthen the hypothesis, and the results of finite element analysis are demonstrated to provide quantitative estimates for the time-delayed increase in the sand penetration resistance.