冀西北地区凝灰岩吸水及膨胀特性研究

Study on water absorption and expansion characteristics of tuff in Northwest Hebei

以京张高铁某隧道工程提供的膨胀性凝灰岩为研究对象,采用改进设计的岩石连续吸水膨胀力试验仪,对凝灰岩的吸水及膨胀特性进行了试验研究。以湿度应力场理论为基础,从理论上推导了凝灰岩膨胀力与含水率关系,并对试验结果进行了验证,结果表明:(1)凝灰岩的饱和吸水率为15.91%~17.83%,吸水率随着时间的增长而呈现出对数增长,吸水特征曲线可以分为3个阶段:快速吸水阶段、减速吸水阶段、残余吸水阶段;(2)凝灰岩饱和吸水膨胀力为81.87 kPa^95.4kPa,膨胀力随着时间的增长而呈现出对数增长,且具有滞后效应;膨胀特性曲线分为3个阶段:快速膨胀阶段、减速膨胀阶段、残余膨胀阶段;(3)根据推导的公式,工程上可通过测定含水率来估算凝灰岩膨胀力的大小。

Taking the expansive tuff provided by a tunnel project of Jing Zhang high-speed railway as the research object,an experimental study on the water absorption and expansion characteristics of the tuff is carried out by an improved continuously absorbing water testing instrument.Based on the theory of humidity stress field,the relationship between expansion pressure and water content is derived theoretically,which verifies the test results.The results show that:(1)The saturated water absorption of tuff is about 15.91%~17.83%,and the water absorption increases logarithmically with time.The characteristic curve of water absorption can be divided into rapid,slow and residual water absorption stages;(2)The tuff saturated water absorption of expansion pressure is about 81.87kPa^95.4kPa.The expansion pressure increases logarithmically with time with a hysteresis effect.The expansion curve is divided into rapid,slow and residual expansion stages;(3)According to the derived formula,the expansion pressure of tuff can be estimated by measuring the water content in engineering applications.