地铁列车荷载作用下隧道周围土体的临界动应力比和动应变分析

CRITICAL DYNAMIC STRESS RATIO AND DYNAMIC STRAIN ANALYSIS OF SOILS AROUND THE TUNNEL UNDER SUBWAY TRAIN LOADING

通过南京地铁三山街站隧道周围淤泥质粉质粘土进行应力控制的循环三轴试验,研究了列车循环荷载作用下淤泥质粉质粘土的动应变发展情况,充分考虑了土体固结状态、固结比、轴向循环压力的大小及频率对动应变的影响。得到了淤泥质粉质粘土的临界动应力比和动应变随振动次数、加载频率和围压及固结状态而变化的规律,对地铁隧道的设计具有重要参考价值。

Through the dynamic triaxial tests of silt soils around the tunnel of Sang-Shang station, Nanjing subway, the dynamic strain analysis is made on the silt soils under subway train loading. The influence of consolidation status of soils, consolidation ratio, axial cyclic stress, vibration frequency are taken into account. The variation rules are obtained of the critical dynamic stress ratio of the silt soils and dynamic strain with vibration times, vibration frequency, confining stress and axial stress. Some conclusions are made from the research as following. (1) There is a critical dynamic stress ratio under train vibrating loading, which depends on soil property, loading characteristic and consolidation pressure. Soil deformation increases with cyclic times when applied loading is less than the critical dynamic stress. But the increasing rate slows down until it trends to a constant value. On the contrary, the deformation increases quickly with cyclic times until soil is destroyed. (2) In the same vibration condition, the higher the frequency is applied, the less the deformation is induced. The critical dynamic stress ratio decreases gradually with growing of frequency and there is an asymptote. (3) With the same axial consolidation pressure and dynamic stress, the larger consolidation ratio is, the larger ultimate deformation is, and the easier it is to make sample destroyed.