摘要
隧道近接下穿3层倾斜采空区施工容易引起围岩松动范围叠加、增大,地层的非对称移动易使隧道结构受非对称荷载作用。采取室内模型试验模拟公路隧道下穿3层煤层采空区的开挖过程,通过埋设土压力盒、电阻应变片、地中位移计,测量隧道开挖过程中初期支护受力和地层位移。试验结果表明,一定范围倾角越小,隧道测试断面开挖过程中的采空区地层的沉降速率越大,时程曲线越陡,后期沉降值较大,扰动程度随地层与隧道距离的增加先增大后减小;一定倾角的采空区会使离采空区较远一侧的仰拱处土压力明显增大,结构设计时应予以加强;在15°~30°范围内,倾角对围岩压力的分布形态、量值影响不大,对钢拱架内力影响较大,倾角越大,初期支护偏心距越大。对于Ⅳ级围岩,双车道隧道近接(2 m)3层采空区地层施工时,建议先进行超前支护,再采用台阶法开挖,进尺不大于1 m,钢拱架间距不大于0.5m。
The looseness range of surrounding rock is easy to overlay and enlarge when tunnelling adjacently underneath triple-decker mined-out area, the asymmetric movement of formation may lead to asymmetric loads to tunnel structure. Indoor similarity model test of tunnel excavation underlying triple-decker mined-out area was carried out; the ground movement of the mined-out area and internal forces of the primary supporting structure were gauged with the displacement meters, the earth pressure cells and the electric resistance strain gauges embedded in the earth. Test result of displacement predicts that in a specific dip angle range the smaller dip angle of mined-out area will cause larger settlement rate, steeper curve, slower convergence speed later and bigger settlement value. With the increase of distance between the strata and tunnel, strata disturbance degree first increases and then decreases; a certain angle of mined-out area will make the earth pressure of one side of the inverted arch where relatively far from the mined-out area significantly larger than another side; therefore, the inverted arch's structure design should be strengthened. In the range of 15 °to 30°, the existence of dip angle has little influence on distribution form and size of surrounding rock pressure; but greatly affects the internal forces of the steel arch; the larger the angle is, the bigger the primary support eccentricity is. For the fourth grade of surrounding rock, when two-lane tunnel is built adjacently(2 m) underneath triple-decker mined-out area, it's strongly recommended to support in advance, then excavate by steps method, excavation footage should be not more than 1m, steel arch span should be not more than 0.5 m.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2014年第S2期257-266,共10页
Rock and Soil Mechanics
基金
国家自然科学基金(No.51278422)
国家科技支撑计划课题(No.2012BAG05B03)
四川省青年科技基金(No.2012JQ0021)
中央高校基本科研业务费专项资金(No.SWJTU11ZT33)
关键词
公路隧道
3层采空区
模型试验
地层移动
初期支护内力
highway tunnel
triple-decker mined-out area
model test
ground movement
primary support
