Study on the Influence of Smear Zone Surrounding Prefabricated Vertical Drains to Performance of Consolidation

Abstract

This project studies the influence of smear zone on the installation of prefabricated vertical drains that affects the distribution efficiency of excess water pressure. During application vacuum consolidation for the improvement of soft Bangkok clay. In the analysis, the perimeter of disturbed soil around PVD was divided into (iii) main zones: (i) (Highly disturbed zone), (ii) Marginal disturbance zone., and (iii). Insignificant disturbance zone (Rujikiatkamjorn 2008) In each zone there is a different value of water permeability in the soil masses. and a linear decrease towards PVD (Indraratna et al. 2014). To study all 3 paramete rs as follows: 1) the ratio between the distance of the disturbed soil (Smear zone) and the size of the mandrel (Extent Ration), ds/dm is between 2 and 5 times 2) The permeability ratio of the smear zone and the undisturbed zone, kh/ks, was between 2 and 6 times, and 3) Divided the number of smear zones into 2 to 5 zones [11] By analyzing to compare the values of excess water pressure generated in each sample case. The finite element method by Plaxis 2D software, The results from the study of considering the effect of the smear zone from the installation of the prefabricated vertical drains (PVD) showed that the value of kh/ks had the greatest effect on the settlement rate compared to the last settlement value at specified time The difference was about 3 percent The effect of ds/dm had an effect on the settlement rate compared to the final settlement at the specified time. There was a difference of about 1 percent and the effect of dividing the number of disturbed soil boundaries around PVD, n if ignoring the effect of disturbed soil (Smear Zone), was found 7 percent higher than the subsidence value, respectively.