以砂箱試驗探討MICP工法對於土壤改良之成效

Abstract

台灣因位處歐亞板塊及菲律賓海板塊交界之環太平洋地震帶上，故地震相當頻繁，而當大規模地震發生時，常伴隨土壤液化產生並帶來嚴重災情，而隨著人口密度越來越高，對於土地利用之需求也與日俱增，原先傳統之低矮建物，漸漸開始由密集之高樓大廈所取代，因此進行土壤改良刻不容緩。本研究使用一種環境友善且具經濟性之地盤改良工法: 微生物誘導碳酸鈣沉澱 (Microbially Induced Calcite Precipitation) ，簡稱 MICP，該工法應用土壤中之細菌進行砂粒固結，藉此改善軟弱土壤之工程性能。本研究針對三種尺度進行MICP改良成效探討，分別為表面滲透之小型砂箱試驗、側向加壓滲透之中型砂箱試驗、側向加壓滲透之現地試驗。第一種小型砂箱試驗，將符合標準靜三軸試驗規格設計之取樣器A埋入後填砂，進行表面MICP改良液滲透，待七日養護完畢後，由酸洗試驗及靜三軸試驗結果顯示具有均勻且整體強度提升之改良成效。第二種中型砂箱試驗，將不產生側壁溶液阻擋之取樣器B埋入後填砂，進行側向MICP改良液加壓滲透，待七日養護完畢後，由酸洗試驗可以觀察到在400 kPa側向加壓下，有效改良範圍符合預期之走向。第三種現地試驗，將取樣器A及澆灌管線輔助壓克力基座埋入，進行側邊雙向MICP改良液加壓滲透，待七日養護完畢後，因現地試驗之不可控因素相當多，由酸洗試驗結果發現大部分取樣點仍有明顯之碳酸鈣結晶生成，顯示該澆灌系統之設計可以有效地將改良液滲透進土壤中。

As Taiwan is situated on the Circum-Pacific Seismic Belt, where earthquakes happen frequently and can lead to soil liquefaction, resulting in severe disasters. As the population density continues to increase and the demand for land use grows, traditional low-rise buildings are gradually being replaced by densely packed high-rise buildings. Therefore, soil improvement is urgently needed. This study employs an environmentally friendly and cost-effective ground improvement technique called Microbially Induced Calcite Precipitation (MICP). MICP utilizes bacteria present in the soil to consolidate sand particles, thereby improving the engineering properties of weak soils. The effectiveness of MICP improvement was investigated at three scales: small-scale sandbox tests with surface infiltration, medium-scale sandbox tests with lateral pressure infiltration, and field tests with lateral pressure infiltration. In the small-scale sandbox test, sampler A, designed according to standard consolidated drained triaxial test specifications, was buried and filled with sand. After a seven-day curing period, the results of acid digestion tests and consolidated drained triaxial tests indicated a uniform and overall increase in strength due to the improvement. In the medium-scale sandbox test, sampler B, designed to prevent sidewall solution blockage, was buried and filled with sand. After a seven-day curing period, acid digestion tests revealed that the effective improvement range matched the expected trend under a lateral pressure of 400 kPa. In the field test, sampler A and an acrylic base with watering pipelines were buried. After a seven-day curing period, due to numerous uncontrollable factors in the field test, acid digestion test results showed significant calcium carbonate crystal formation in most sampling points, indicating that the design of the watering system effectively allowed the improvement solution to permeate the soil.