闽南风化凝灰熔岩强度特性的试验研究

Experimental Analysis on the Strength Properties of Weathering Tufflava in the South Fujian Province

对福建闽南地区泉三高速公路隧道围岩中的风化凝灰熔岩进行了吸水率和单轴抗压强度试验,定量分析了风化程度对岩石单轴抗压强度和吸水特性的影响,并得出了不同风化程度的凝灰熔岩其吸水率与烘干状态和饱和状态下的单轴抗压强度之间的非线性关系式。该式可以为类似条件下岩石强度估算提供参考和借鉴。

As an important component of the Mesozoic volcanic rock in China,tufflava is widely distributed in the provinces of Guangxi,Fujian,Zhejiang,and Guangdong,and in Mesozoic volcanic basins of the Middle to Lower Yangtze River area.Because of its special material composition and structure construction,tufflava is easy to weather under all kinds of exterior geological agents,such as water and atmospheric conditions.Usually many construction projects,especially tunnel excavations,will inevitably pass through this kind of rock mass.Therefore,it is very important to study the property of weathering tufflava for the design,construction,and stability analysis of tunnel engineering,as well as other engineering projects.This paper researches weathering tufflava,which belongs to the tunnel surrounding the rock of the Fujian Quanshan Highway in the south Fujian province.Uniaxial compressive strength and water absorption experiments are conducted on tufflava with different weathering degrees （strong weathering,weak weathering,slight weathering,and unweathering tufflava） with the intent to quantitatively analyze the effect of the degree of tufflava weathering on the uniaxial compressive strength and water absorption characteristics.The process for the experiments can be described as follows.Based on the standard test method for engineering rock masses,38 pieces of standard samples （50 mm× 50 mm× 100 mm） were prepared,with the drying and saturation processes strictly performed by the standard.There are two ways,boiled saturation and natural saturation,to saturate tufflava with different weathering degrees in water absorption experiments.In addition,strength tests of tufflava with different weathering degrees under air-drying and saturated conditions were conducted by the model YAW-2000 pressure tester.During the strength tests,we chose load control mode and set the maximum axial compression to 1 000 kN and the loading speed to 0.75 MPa/s.The relationship between water absorption and the weathering degree under the conditions of boiled saturation and natural saturation were obtained.In addition,the relationship between strength and weathering degree under the conditions of air-drying and saturation were also obtained.It was found that the degree of weathering has a significant effect on the water absorption property and uniaxial compressive strength.The stronger the weathering degree is,the higher the water absorption shows,and the smaller the uniaxial compressive strength is.Finally,we fit the analysis of the uniaxial compressive strength and water absorption based on the data which has also been studied by using logistic regression models.The results show that the uniaxial compressive strength of tufflava with different weathering degrees under air-drying and saturation conditions has a nonlinear relationship with water absorption.The maximum error is 14 %,which can completely meet the project accuracy requirements.This non-linear relationship formula can be applied to strength estimations of rocks similar to the weathering tufflava in this paper.