爐石水泥改良高嶺土之動態性質

Abstract

當土木工程在軟弱地盤上施工時，通常會使用地盤改良工法來增加土層之強度與勁度，灌漿工法便是一種常採用之改良工法，通常使用水泥以漿體的形式注入土層中，藉由水泥之遇水產生硬化，提升改良區域之強度並減少可施工時的沉陷量，近年來，會適量地在水泥中加入高爐石與飛灰等卜作蘭材料，減少水泥之用量以及避免高爐石與飛灰此類工業副產物的廢棄而造成之環境汙染問題。 本研究使用將三種不同之爐石水泥含量(C/S ratio = 15%、20%、25%)配以三種不同之黏土含水量(ω = 1.8LL、2.0LL、2.2LL)與高嶺土混合，爐石水泥含量之定義為乾爐石水泥與乾黏土之重量比，而含水量部分則是1.8、2.0、2.2倍之黏土液性限度，以此模擬軟弱土壤的狀態。試體尺寸為直徑7公分以及高度15公分，所有試體在養護7、14、28、56天之後進行共振柱試驗以量測不同養護時間時的動態性質，進行共振柱試驗時會採用80、160、320 kPa等三種不同之圍壓，觀察不同圍壓下動態性質的變化。 實驗結果顯示，本研究之改良黏土之剪應變範圍在10-5 % 到 10-2 % 之間，而門檻剪應變在10-4 % 到 10-3 % 之間。圍壓與爐石水泥含量的提昇以及含水量的減少會使得剪力模數增加，然而在阻尼比方面，圍壓、水泥含量以及含水的影響則不明顯，此外，隨著養護天數的增加，剪力模數會提升而阻尼比會下降。由此可知，土壤之勁度會因為添加爐石水泥而產生勁度增加的效果，因此，本研究所使用之爐石水泥為一種有效的地盤改良材料。

Because of its low strength, soft ground is usually improved to increase strength stability and decrease settlement. Grouting is one of the ground improvement method, which adds reinforcing materials into ground. Portland cement is a common material to be used for soft ground improvement. In addition, some additives have been used to replace part of the cement due to their economic and environmental advantages, such as slag and fly ash. In this study, the Kaolinite and slag cement were obtained in dry powder initially. Engineering properties of this clay including specific gravity, liquid limit, and plastic limit were examined first. Afterwards, the clay was mixed with different amount of slag cement and water. The clay water content, ω, is defined as the weight of water in clay to dry weight of kaolinite. The slag-cement content is defined as the dry weight of slag cement to dry weight of kaolinite, which is written as C/S ratio. Three different C/S ratios and three different clay water contents were used. The resonant column tests with three different confining pressures were carried out in this study. The specimen size is 7 cm in diameter and 15 cm in height. All the specimens in this research are tested at curing time of 7, 14, 28, and 56 days. The effect of shear strain, confining pressure, cement content, water content and curing time on shear modulus and damping ratio of stabilized clay were discussed. The range of shear strain is from 10-5 % to 10-2 % with the threshold shear strain ranging from 10-4 % to 10-3 %. The shear modulus increases slightly with increasing confining pressure. However, confining pressure has a little influence on damping ratios. The shear modulus increases with increasing in slag-cement content but decreases with increasing in water content. On the other hand, the effect of slag-cement content and water content on damping ratio is not apparent. After curing, the maximum shear moduli increase and the minimum damping ratios decrease. Thus, the stiffness of stabilized clays enhance. As a result, the slag cement used in this study is an effective material in ground improvement.