生土墙体的抗火性能

生土属于A级完全不燃烧建筑材料。尽管火灾（高温）提高强度，但消防射水引起受火后生土急冷收缩，力学性能劣化；已有的研究表明受火墙体截面温度梯度会导致材料不均匀变化，重力载荷下面外失稳。以生土火灾（高温）损伤机制为核心，通过火灾（高温）材料性能测试，建立应力-温度耦合本构关系计算方法。结合生土墙体耐火试验、火灾（高温）后生土墙体轴压、偏压、抗震性能试验、理论分析和数值模拟，考察组成成分、密实度、外覆石灰层厚度、初始应力、升温速率、最高温度及持续时间、冷却方式和室内室外等因素对墙体耐火极限的影响，揭示火灾（高温）后生土墙体的破坏机理；给出生土墙体隔热性、完整性和承载能力的建议判断标准，建立耐火极限与墙体等效厚度的关系；提出生土墙体抗火性能评价方法和灾后剩余承载力模型。生土墙体抗火性能是防火设计、灾后性能评价、损伤鉴定及加固修复的基础。对确保生土结构火灾安全性和推进生土材料的实际应用具有重要意义。

Raw soil is a Class-A building material that is completely non-combustible. Although fire (high temperature) increases the strength of raw soil, conventional fire hoses may cause serious degradation of raw-soil performance when extinguishing the fire. Existing studies have shown that the thermal gradients of walls exposed to fire can cause uneven material degradation of structural sections and eccentric instability under gravitational loads. With the damage mechanism of raw soil under fire as the core and through examining material performance test under fire, a method for calculating stress-temperature coupling constitutive model is developed. A number of tests including fire resistance test, axial compression, eccentric compression, and seismic pseudo-static tests of earth walls after fire will be done. Using the tests, theoretical analysis, and numerical simulation, the way soil composition, compaction, lime protective layer thickness, initial stress, heating rate, maximum temperature and duration, cooling method, indoor or outdoor fire, and other factors influences maximum fire resistance of walls is examined. The failure mechanism of earth walls after fire is revealed. Then, a procedure for evaluating thermal insulation, integrity, and bearing capacity of earth wall is proposed. The relationship between fire resistance limit and equivalent thickness of the wall is established. A post-disaster residual bearing capacity model and a method for evaluating fire resistance of earth walls is put forward. Fire resistance of earth walls is a prerequisite for fire protection design, post-disaster performance evaluation, damage identification, reinforcement and repair. It is of great significance to ensure fire safety of earth buildings and promote practical applications of raw-soil materials.