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以在建穿越5·12汶川强震区成都至兰州高速铁路站前试验段某隧道大变形极高风险段为工程依托,运用现场试验与数值模拟手段,针对传统的型钢拱架和新型自主研发的钢格栅混凝土核心筒支护结构体系,分别对围岩收敛变形、围岩深部位移、围岩与初支接触压力、拱架内力、锚杆轴力、初支与二衬接触压力以及二衬轴向应变变化特征与规律进行研究。研究结果表明:(1)强震区千枚岩隧道,传统的型钢支护可硬性约束围岩前期变形,但后期变形增长迅速,未呈现收敛趋势,如拱顶沉降随施工开挖呈现明显的三台阶波动加速增长,累积值达323mm,超出预留变形量(250 mm),初支封闭成环7 d后,拱顶及拱肩出现局部喷层开裂、掉块;围岩浅部和深部位移近似呈倒三角型分布,最大值178 mm发生在右边墙;拱架与围岩接触压力前期增长较快,其后拱架背后围岩向两侧挤出,压力增长放缓;除右拱肩和左边墙3.5 m处锚杆受拉外,其余全受压,最大值为拱顶锚杆0.5 m处22.4 k N,峰值均出现在浅部围岩锚杆0.5 m左右断面处;二衬承载比例系数约为2.55;(2)新型支护结构下围岩前期变形增速快,如拱顶沉降达70.3 mm,约为原支护拱顶沉降的41.3%;混凝土核心筒约束后期变形,28 d后变形收敛稳定,稳定值小于预留变形量;围岩内部位移主要集中在浅部2.5 m深度范围内,约为深部位移的8.1~8.5倍;拱架与围岩接触压力增长平缓,趋于收敛,终值为202 k Pa;锚杆轴力峰值出现在锚杆长度的1/2左右处,满足锚杆峰值中性点理论;考虑二衬混凝土浇筑压力,衬砌受力较小;(3)结合数值模拟与现场试验结果,钢格栅混凝土核心筒支护结构体系可有效控制强震区软弱破碎围岩隧道大变形,结构体系变形及受力合理,可为类似工程建设提供借鉴。
In order to build a very large risk section of a tunnel in the pilot section of Chengdu-Lanzhou High-speed Railway Station crossing the 5.12 Wenchuan earthquake zone, based on the project, field tests and numerical simulation methods were used to solve the problems of traditional steel arch arches and new independent research and development Of the steel grid concrete core tube supporting structure system, respectively, the convergence and deformation of the surrounding rock, deep displacement of surrounding rock, contact pressure of surrounding rock and the initial branch, arch internal force, anchor axial force, the contact pressure of the first branch and the second branch, The characteristics and regularity of axial strain change of lining are studied. The results show that: (1) In the strong earthquake zone, the phyllite tunnel and the conventional steel support can rigidly constrain the deformation of the surrounding rock at the early stage, but the deformation at the later stage increases rapidly and does not show the convergence tendency. For example, The fluctuation of the three steps accelerates with an accumulated value of 323 mm, exceeding the preset deformation (250 mm). After the first branch is closed into a ring for 7 days, the local spray layer cracks and falls off on the vault and arch shoulder. The shallow and deep part of the surrounding rock Displacement approximately inverted triangular distribution, the maximum 178 mm occurred in the right side of the wall; arch and surrounding rock contact pressure increased rapidly in the early period, then the back of the arch surrounding rock extrusion to both sides, the pressure growth slowed; except the right arch At the shoulder of 3.5m at the shoulder and the left wall, the rest of the bolt was tensioned except for the tension of 22.5 kN at 0.5 m of the roof anchor. The peak appeared at the cross section of the surrounding rock bolt about 0.5 m. The bearing ratio coefficient is about 2.55; (2) The deformation of the surrounding rock under the new type of supporting structure increases rapidly, for example, the vault settlement reaches 70.3 mm, which is about 41.3% of the settlement of the original supporting vault; the concrete core tube restrains the late deformation, After 28 days, the deformation converges and the stability value is less than the reserved deformation. The internal displacement of the surrounding rock mainly concentrates in the depth 2.5 m Which is about 8.1 ~ 8.5 times of the deep displacement. The contact pressure between the arch and the surrounding rock increases gently and converges to the final value of 202 kPa. The peak value of anchor force appears at about 1/2 of the length of the anchor. (3) Combined with numerical simulation and field test results, the steel grid concrete core tube supporting structure system can effectively control weak areas in strong earthquake area Large deformation of crushed rock tunnel, deformation of structural system and reasonable stress can provide reference for similar projects.