活性氧化镁碳化搅拌桩模型试验研究

Model tests on carbonated reactive MgO mixing piles

软弱土须经适当的人工处理才能满足建筑和基础设施的承载需要,而MgO碳化搅拌桩法是一种创新型的地基处理技术,即将CO_2气体通到拌有活性MgO的搅拌桩体中,通过一系列物理化学反应,形成稳定性好、承载力高的复合地基。基于此,采用人工挖孔制桩法,开展了不同初始含水率和不同CO_2通气压力下室内搅拌桩模型试验,碳化过程中进行桩体温度监测,碳化后对桩体进行无侧限抗压强度和含水率测试。结果表明:搅拌桩温度在不足2h碳化时间可达到最高,且峰值温度在初始含水率为20%时最高、在15%时次之、在30%时最低;峰值温度随CO_2通气压力增加而增加。碳化搅拌桩强度随初始含水率增加而减小,随CO_2通气压力增加而增加,且强度随含水率呈指数形式递减。碳化搅拌桩模型试验将为MgO碳化技术在软土地基加固工程中的应用提供理论指导。

The soft soils can meet the bearing needs of the constructions and infrastructures through the appropriate artificial treatment, and the carbonated MgO-mixing pile method is an innovative foundation treatment technology, which is that the reactive MgO-mixing pile takes a series of physical and chemical reactions with CO_2 gas, forming a composite foundation with good stability and high bearing capacity. On this basis, the indoor mixing pile model tests are carried out under different initial water contents and different CO_2 ventilation pressures by use of the artificial dig-hole pile method, and the temperature of mixing piles is monitored during the carbonation process, as well as these tests are performed after carbonation including unconfined compressive strength and water content. The results indicate that the pile temperature can reach the highest in less than two hours' carbonation, and the temperature peak is the highest at the initial water content of 20%, the second at 15% and the lowest at 30%. The temperature peak increases with the increase of CO_2 ventilation pressure. The strength of carbonated piles decreases with the increase of the initial water content while increases with the increase of the CO_2 ventilation pressure, and the strength decreases with the water content of the carbonated soils in the form of exponential function. The carbonated mixing-pile model tests will provide theoretical guidance for the MgO-carbonation technology in the engineering application of soft soil foundation reinforcement.