基于SEM图像的灰土力学模型研究

灰土是古建筑常用的材料,因文物保护的要求,灰土取样受一定的限制,因此建立合适的力学分析方法对研究灰土及古建筑本体的力学性能具有重要意义。依据土的三相介质组成和微观尺度构成,将灰土分为颗粒、胶结物和孔隙三部分; 基于300倍SEM微观结构和图像处理技术构建了灰土力学模型,根据粒径组成和试验测试数据分析了胶结物的受力特性,得到了胶结物的塑性损伤模型,并进行了灰土模型的单轴力学性能仿真; 基于室内胶结试验结果建立了胶结物与含水率的应力-应变关系式。研究结果表明:灰土土样单轴压缩试验结果与基于微观尺度灰土分析模型的模拟结果相对吻合,验证了基于SEM分析模型进行灰土力学分析的可行性; 在一定含水率范围内,0.075 mm和0.1 mm粒径胶结物应力-应变变化规律基本保持一致; 在单轴压缩荷载作用下,试件颗粒与胶结物界面处及孔隙周围首先出现损伤破坏并产生裂缝,其主要原因是该区域存在应力集中现象,随着荷载继续增大,损伤区域向外扩展延伸,形成斜向连贯的断裂带,最终导致试件破坏。

Study of Lime Soil Mechanical Model Based on SEM Images

Lime soil is commonly used in ancient buildings. Due to the requirements of cultural relics protection, the sampling of lime soil is limited. Therefore, it is of great significance to establish a suitable mechanical analysis method for studying the mechanical properties of lime soil and ancient buildings. According to the composition of three-phase medium and micro-scale of soil, the lime soil was divided into three parts: particles, cementations and pores. Based on the 300 times SEM microstructure and image processing technology, the lime soil analysis model was constructed. According to the particle size composition and the test data, the stress characteristics of the cementation were analyzed, the plastic damage model of the cementation was obtained, and the uniaxial mechanical properties were simulated. Based on the laboratory cementation test results, the stress-strain relationship between cementation and water content was established. The study results show that the uniaxial compression test results of lime soil samples are consistent with the numerical simulation results based on the micro-scale lime soil analysis model, which verifies the feasibility of the mechanical analysis of lime soil based on the SEM analysis model. Within a certain range of water content, the stress-strain variation laws of 0.075 mm and 0.1 mm particle size cements are basically consistent. Under the action of uniaxial compression load, the damage failure and cracks firstly appear at the interface between particles and cements and around the pores. The main reason is that there is stress concentration in this area, and with the increase of load, the damage area extends outwards, forming an obliquely coherent fault zone, and finally leading to the failure of the specimen.