CREEP EFFECT OF LOESS STRATA ON SURROUNDING ROCK PRESSURE OF TUNNELS
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摘要: 以某黄土地区公路隧道为研究对象,通过室内单轴蠕变试验来探索不同含水率下原状Q2黄土的蠕变规律及参数,并基于数值方法分析隧道地层在长期变形效应下的围岩压力及收敛变形演化规律,最后提出考虑长期变形效应的围岩压力分布模式及计算方法,得出:1)黄土地层发生长期变形期间,围岩压力及竖向收敛变形均呈增大趋势,蠕变10 a后,围岩压力基本趋于稳定,围岩压力呈"猫耳朵"形分布。竖向和水平围岩压力平均放大1.61倍和1.33倍,拱顶沉降平均放大1.22倍,水平收敛位移平均减小0.97倍;2)随着隧道埋深的增加,因土体蠕变引起的洞周围岩压力比和收敛变形比总体呈增大趋势,埋深增大会导致围岩应力及变形放大效应更明显;3)地层初始含水率越大,洞周围岩压力及收敛变形量越大,但围岩压力比和收敛变形比反而呈减小趋势;4)将围岩压力比参数引入到Terzaghi理论和谢家烋算式中,提出了修正的围岩压力计算式,可考虑黄土地层长期变形引起的围岩压力放大效应。Abstract: Based on a highway loess tunnel, the uniaxial creep tests of undisturbed Q2 loess in the different moisture content were conducted to explore the creep properties, and the effect of long-term deformation on the evolution laws of surrounding rock pressure and convergence deformation were analyzed by numerical methods, finally, the distribution modes and calculation methods of surrounding rock pressure were put forward. The results showed that:1) in the course of long-term deformation development of loess strata, the surrounding rock pressure and vertical convergence deformation all showed a trend of increase. 10 years later, the surrounding rock pressure would keep it stable, and the distribution form would be in the "cat's ear" shape. The average magnifications of vertical and horizontal surrounding rock pressure were 1.61 and 1.33, the average vertical subsidence of the arch crown was magnified by 1.22 times and horizontal convergence deformation was reduced by 0.97 times respectively;2) with the increase of tunnel embedment, the ratios of surrounding rock pressure and convergence deformation generally increared, and increase of embedment, the magnified effects on stress and deformation were more obvious; 3) the greater the initial moisture content of the loess, the greater the surrounding rock pressure and convergence deformation, but the ratios of them tended to decrease;4)the surrounding rock pressure ratio was introduced into Terzaghi theory and XIE Jiaxiu's formula, the modified formula of surrounding rock pressure were put forward, and the long-term deformation effect of loess strata on the surrounding rock pressure could be considered.
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Key words:
- loess stratum /
- tunnel /
- surrounding rock pressure /
- creep effect
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