Abstract
Due to the special mechanical properties of macker rock, problems may be caused easily if the pressure of the surrounding rock calculated from the standard empirical equation is used in the structural design of tunnel support, such as obviously insufficient bearing capacity of the support structure, large deformation, and collapse. Taking the Jiangluling Macker Tunnel in Gonghe-Yushu Highway as an example, the distribution pattern of plastic zone of the surrounding rock and the calculation method and reasonable values of pressure of the surrounding rock are studied in this paper, by means of theoretical analysis, numerical computation, and field measurement data. The results show that the elastic-plastic analysis method is suitable for the pressure of the surrounding rock of macker tunnel. The influence radius of the plastic zone of the surrounding rock can be 32 m, and the lateral pressure of the surrounding rock of the tunnel is equivalent to the vertical pressure. In the absence of test conditions and measured data, the pressure of the surrounding rock can be approximately 0.83 MPa for the purpose of design of tunnel support structure. This conclusion provides technical support for projects in similar conditions.
Highlights
In China’s Western Development Program, the buildup of a convenient transportation system is the necessity for economic development and social progress in the western region and the improvement of land traffic network requires expansion of transportation infrastructure into naturally severe, high-latitude, and high-altitude cold regions
Due to lack of understanding of the mechanical properties of the surrounding rock of high-altitude macker [1], the distribution pattern of the plastic zone of the surrounding rock [2, 3], the variation law of the pressure of the surrounding rock, and the reasonable values of the pressure of the surrounding rock are unclear when the tunnel support structure is designed, resulting in engineering problems occurring in the process of tunnel construction, such as large deformation, extrusion and collapse of the surrounding rock, uplift of tunnel bottom, cracking of support structure, and deformation and damage of lining
According to the results of the two test methods, the plastic zone radius of the surrounding rock in the Jiangluling Macker Tunnel is greater than 8 m, which is demonstrated by numerical analysis as follows
Summary
In China’s Western Development Program, the buildup of a convenient transportation system is the necessity for economic development and social progress in the western region and the improvement of land traffic network requires expansion of transportation infrastructure into naturally severe, high-latitude, and high-altitude cold regions. E majority of domestic studies on macker tunnel focus on mechanical properties, deformation rules and deformation mechanism of the surrounding rock [4], instability failure mechanism, and engineering treatment measures [5]. Rough statistical analysis of field measured data, working face sketching, and application of theories about engineering geology and structural mechanics, Tian Siming analyzed the deformation and damage mechanism of high-geostress macker, discussed the impact of bedded rock and soft rock strata on the stability of tunnel surrounding rock, and revealed the mechanical mechanism of deformation and damage of high-geostress macker [8]. There is little research on reasonable values of pressure of the surrounding rock of the macker tunnel [11, 12], which is very disadvantageous to engineering design
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