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| Stress-strain characteristics and effective range of improvement under dynamic compaction based on capped yield hardening model |
| YAO Zhanyong1，ZHOU Chong1，JIANG Hongguang1，BI Yufeng2，SUN Menglin1，ZHOU Leisheng3，QI Hui3 |
| (1. School of Civil Engineering，Shandong University，Jinan，Shandong 250061，China；2. Shandong Provincial Communications Planning and Design Institute，Jinan，Shandong 250031，China；3. Qilu Transportation Development Group，Jinan，Shandong 250101，China) |
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Abstract In order to investigate the stress-strain characteristics of soil and the effective range of reinforcement under dynamic compaction，a two-dimensional dynamic model based on the capped yield hardening model was established and implemented through finite element method. A subroutine was programmed to simulate the parameters such as the soil modulus changing with the ramming times. With the proposed numerical model，the soil stress path in p-q plane( p is principal stress，q is deviatoric stress) and the stress-strain relationship in both vertical and horizontal directions were firstly obtained in the simulation of successive dynamic compaction. Results indicated that the cap surface expanded with the soil densification but that the reinforcement processes varied with the soil locations due to the different characteristics of the stress-strain relationship. Soils right under the pounder were mainly compressed in the vertical direction caused by the higher vertical stresses. However，the development of horizontal deformation at the shallower depths lagged behind the vertical deformation due to the effect of lateral inertia，while the deformation at the deeper locations developed simultaneously in both horizontal and vertical directions. Soils beside the pounder were mainly compressed in the horizontal direction due to the much larger lateral stresses. Then the reinforcement effect was quantitatively characterized by the relative distance between the peak value of the deviatoric stress and its front cap surface. When the deviatoric peak stress located above the cap surface，soils experienced the yield hardening. Otherwise，soils would not be compressed. Finally，the effective improvement ranges determined by the criterion of 90% compaction degree were found to be more conservative than those by the criterion of 5% relative density increment. Empirical formulae were put forward to predict the effective ranges of improvement for the sand foundation.
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2018, Vol. 37 
