以數值程式 PLAXIS 分析垂直排水帶對 地盤壓密之影響

Analysis of the Influence of PVDs on Ground Consolidation by Using PLAXIS

羅于智(Yu-Chih Lo)

指導教授 ： 馮道偉

中原大學/工學院/土木工程學系/碩士(2006年)

https://doi.org/10.6840/cycu200600555

摘要

中文摘要
預壓及垂直排水帶為地盤改良工法之ㄧ，在改良軟弱黏土時較常
被使用。本研究之主要目的係針對預製式垂直排水帶在軟弱土層之地
盤改良等相關問題，利用有限元素程式PLAXIS 進行數值模擬分析，
此一程式尚未內建可資分析垂直排水預壓之功能。本研究以PLAXIS
程式之建構元素功能，模擬垂直排水帶加速地盤壓密，主要研究課題
包括：(1) 垂直排水帶打設深度對壓密沉陷之影響；(2)垂直排水帶打
設間距對壓密沉陷之影響；(3) 塗抹效應對壓密沉陷之影響；(4) 井
阻效應對壓密沉陷之影響；(5) 曼谷第二國際機場之預壓及垂直排水
現地案例之數值分析。
分析結果顯示：(1)在打設深度在欲改良土層厚度之85%以上，
縮短排水帶之間距對於壓密速率有良好之效果；但排水帶打設深度為
改良土層厚度之85%以下時，縮短排水帶之間距幾無效果；(2)考量
塗抹效應下，在kh/ks之比值為2 時，其s 值增加所帶來之影響有限，
但在kh/ks之比值增大至10 時，s 值所來之影響將增大；(3)垂直排水
帶內部之超額孔隙水壓力不等於零，且井阻抗愈大，超額孔隙壓力愈
大；(4)現地案例之計算壓密沉陷曲線及超額孔隙水壓力消散曲線與
觀測結果相近。

關鍵字

垂直排水帶 ； 壓密 ； 井阻 ； 塗抹效應

並列摘要

ABSTRACT
Both preloading and Prefabricated Vertical Drain (PVD) are
methods of ground improvements. Thy are widely used for improving
soft clay. The purpose of this research is to simulate the behavior PVD in
soft clay layer by using Finite Element code PLAXIS. The vertical drain
function has not been built-in in PLAXIS. The main topics of study
include: 1) the influence of PVD installation depth upon consolidation
settlement; 2) the influence of PVD spacing on consolidation settlement;
3) the influence of smear effect on consolidation settlement; 4) the
influence of well resistance on consolidation settlement; 5) case study of
preloading and vertical drain in Second Bangkok International Airport
(SBIA).
The findings indicate: 1) provided the installation depth of PVD is
over 85% of the thickness of improving ground, shortening the distance
of PVD can increase the consolidation rate; but if the PVD installation
depth is below 85% of the thickness of improving ground, there is no
remarkable effect by shortening the spacing of PVDs; 2) concerning with
the influence of smear effect, when kh/ks=2, the influence caused by
increasing s is limited; but when the kh/ks =10, the influence caused by
increasing s will increase; 3) the excess pore water pressure inside the
PVD does not equal to zero, and the higher the well resistance , the higher
is the excess pore water pressure; 4) the estimated consolidation
settlement curve and excess pore water pressure dissipation curve of the
case study are consistent with the observed curve.

並列關鍵字

smear effect ； Prefabricated Vertical Drain ； well resistance ； consolidation

參考文獻

參考文獻

1. 王正吉、沈文忠，「地質改良-垂直排水帶工法及實例介紹」，地工

技術雜誌第63 期，第47-56 頁(1995)。

2. 汪洶均A「土木工程施工學(中)」，大中國圖書公司，第23-42 頁

(1999)。