几类传统改性生土的耐久性及微观结构试验研究

Experimental study on durability and microstructure of several traditional modified soils

改性生土的耐久性对于生土建筑的长期稳定性具有重要意义。本文采用传统的糯米、桐油、稻草、石灰、水泥、细砂作为改性材料,将其按照一定比例单独或混合添加至素土中,通过抗剪强度和渗透性试验来研究其最佳改性材料含量。并开展其自然环境剥蚀试验、毛细水上升模型试验、无侧限抗压强度龄期试验和扫描电镜试验,来探索其耐久性和微观结构演化特征。结果表明:(1)不同改性材料添加至素土中,均存在一个最优改性材料含量,过少或过量添加改性材料均不利于改善素土的强度及抗渗性;改性土的抗剪强度约为素土的1.3~3.5倍,饱和渗透系数约为素土的1/3~1/1650。(2)不同改性土的抗剥蚀性约为素土的1.3~30.0倍,毛细水上升最大高度约为素土的24~93%,糯米基类改性土无侧限抗压强度在7~14 d的龄期上达到最大值,且随龄期的延长而减小,水泥基和石灰基改性土无侧限抗压强度随龄期的延长呈增大趋势。(3)改性土在自然环境下剥蚀后,孔隙面积分布比例(PP)减小幅度约为0.3~5.5%,分形维数(FD)减小幅度约为0.6~3.7%,而素土在发生剥蚀后,其PP和FD减小幅度分别为11.2%和4.3%。

The durability of modified soil is of great significance to the long-term stability of earth buildings.The sticky rice,tung oil,straw,lime,cement and fine sand are used as modified materials,which are added into the plain soil(PS)separately or mixed in a certain proportion,and the optimal proportion is studied through shear strength and permeability tests.Based on the optimal proportion of modified soil,long-term natural denudation test,capillary elevation model test,unconfined compressive strength test by considering age and scanning electron microscopy(SEM)test were carried out to evaluate their regularities of durability and microstructure.The results show that:(1)There is an optimal proportion of modified materials added into the PS.and too little or too much modified materials are not conducive to improve the strength and permeability of PS;The shear strength of the modified soil is about 1.3~3.5 times that of the PS,and the saturated permeability coefficient is about 1/3~1/1650times that of the PS.(2)The denudation resistance of different modified soils is about 1.3~30.0 times of that of PS,and the maximum capillary elevation is about 24~93%of that of PS.The unconfined compressive strength of sticky rice-based modified soils reaches the maximum value at the age of 7-14 days,and then decreases with age.The cement-based and lime-based modified soils shows an increasing trend with age.(3)The porosity percentage(PP)and fractal dimension(FD)of the modified soil decreased by 0.3-5.5%and 0.6-3.7%after denudation in the natural environment,while the PP and FD of the PS decreased by 11.2%and 4.3%,respectively.