【作者】 周烨；

【导师】 刘保国；

【作者基本信息】 北京交通大学 ， 岩土工程， 2013， 博士

【摘要】 兰渝铁路胡麻岭隧道在穿越富水弱成砂岩施工中出现了隧洞周围岩变形大、钢架扭曲失稳、掌子面易坍塌、突泥涌砂等现象。隧道施工难度大,风险高,成为国内罕见、世界性难题。以此为工程依托,论文围绕该围岩变形特征及控制技术等难题,综合采用理论解析、数值模拟、室内模型试验和现场监测等多种研究手段,对隧道施工影响下富水弱成砂岩力学特性及其控制技术进行了系统深入的研究,取得的研究成果如下：(1)通过室内试验得到了富水弱成砂岩的各项物理力学特性参数。结果表明：富水状态的未成砂岩具有较低的粘聚力和渗透性；含水未成砂岩的力学性质与其在干燥情况下极为不同,主要表现为其单轴抗压强度含水后大幅度下降,弹性模量与粘滞系数也随含水量增加而急剧下降。(2)开展了荷载作用下的流变试验。结果表明：其流变应变占总应变的40%左右；含水量不同时蠕变曲线中的瞬时应变、初始流变应变比例及总流变比例也不尽相同。干燥状态下,未成砂岩初始流变占总流变变形的比例在53%左右,而含水状态下其比例均在80%以上。基于以上试验结果拟合了广义开尔文蠕变方程各系数与含水量的关系；推导了弱成砂岩隧道围岩与支护相互作用力的表达式。(3)隧道施工影响下富水弱成砂岩容易出现严重的围岩变形破坏。通常具有变形量大、变形发展快、持续时间长,在时空效应上具有明显的不对称性和不均匀性等特征。对同一断面来说,开挖进程中围岩变形具有明显的阶段性,按变形速率可划分为3个阶段：急剧变形阶段、稳定变形阶段和流变阶段。隧道开挖后围岩变形具有明显时空效应。时间效应主要发生在流变阶段；空间效应通常发生在围岩变形的急剧变形阶段；稳定变形阶段则是两者的过渡段。(4)采用地震折射层析法确定隧道施工影响下富水弱成砂岩松动范围。分析得出：表层波速值低于1000m/s的低速带划为松弛带；中部波速值在1000m/s-2500m/s的渐变区划为松动带；底部波速值低于2500m/s的相对稳定区为未扰动带；各分带之间的界限划分主要以速度梯度带为依据,兼顾波射线的滑行界面位置。(5)基于胡麻岭富水弱成砂岩的特殊力学特性确定了运用超前支护和加固措施。减小或避免围岩变形、尽快使支护结构闭合、按分部顺序采取分割式逐块开挖,并要求边挖边撑以求安全,并辅以监控量测措施。采用数值模拟和工程类比方法确定了胡麻岭隧道主洞的开挖方案和斜井进入正洞挑高段的施工方案,并进行了优化分析。(6)利用有限元对大断面富水弱成砂岩隧道初期支护施作时机进行研究。分析得出：施工中应该以控制围岩变形为核心,在初支结构安全的前提下,强调初期支护施作的及时性；选取富水弱成砂岩隧道典型断面进行现场监测,得出初支、围岩接触压力具有显著时间效应,支护结构设计应考虑其长期流变荷载；在空间规律上,压力分布呈现不均匀性。初期支护与二次衬砌之间的接触压力随时间变化存在一个先增大后减小再增大,并不断趋于稳定的发展过程。初期支护与二次衬砌之间的接触压力分布并不对称,总体上由拱顶→拱肩→拱腰→拱墙-上部→拱墙下部逐渐增大,但拱脚及拱底测值相对较小。(7)胡麻岭隧道富水弱成砂岩具有强度低,遇水的情况下围岩快速软化,自稳能力极差,易坍塌；洞身穿越处水位高经常出现涌砂、突水,沉降大、初支变形等现象；围岩颗粒细小,具有水敏性,富水未固结的情况下具有振动液化现象等工程特性。通过大量的方案论证、工艺试验,最后形成以台阶分部轻型井点降水、深孔负压降水为主的综合降水技术,鉴于水通道或局部囊状流塑状围岩采用双液回退劈裂注浆技术。经过工程现场实践,两种辅助施工技术基本上解决了该套地层围岩稳定问题,有效的控制了围岩变形,在确保施工安全前提下保证了施工进度。更多还原

【Abstract】 During the crossing poorly cemented and water-rich sandstone in Humaling tunnel of Lanzhou-Chongqing railroad, there are big deformation of tunnel surrounding rock,distortion and instability of steel frame, being easy to collapse of tunnel face, burst mud and sand gushing, and so on.Because of tunneling difficult and tremendous construction risk, it is rare in China and be a worldwide problem. Base on this project, this paper research around the surrounding rock deformation features and its control technology by means of theoretical analysis, numerical simulation, indoor model test and field monitoring, then further and systematiac studies the mechanical properties of poorly cemented and water-rich sandstone and its control technology. The several main achievements in the research are as follow:(1) It obtains parameters of physical properties for poorly cemented and water-rich sandstone from indoor experiments, and interactional relationship among them, which is a basis for numerical simulation and the support structure design. The results showed that the poorly cemented and water-rich sandstone have a weak cohesion force and permeability; there are much difference between water-cut poorly cemented sandstone and dry poorly cemented sandstone, which uniaxial compressive strength of water decrease sharply, and the elastic modulus and coefficient of viscosity decreases sharply with the increasing of water content.(2) Through the rheological test of weakly consolidated sandstone which is under load, we found the rheological strain is accounted for40%of the total strain, and when the moisture contents are not the same, the instantaneous strain, the initial rheological strain and the total rheological proportion of the creep curves are also different. In dry surrounding, the initial rheological of unconsolidated sandstone accounts for about53%of the total rheological deformation, and it would be over80%in moisture surrounding. Based on the above test results, the relationship between each coefficients of the general kelvin creep equation and moisture content is fitted, and the creep equation which contains the w coefficient is also derived, the equation aimed at describing the change of the unconsolidated sandstone creep property along with the moisture content; at the same time, the expression of the interaction between weakly consolidated sandstone surrounding rock and supporting is deduced, and through the related expression, the stress, strain and deformation of supporting structure which is under released load are also got.(3) The watery weakly consolidated sandstone prones to heavily deformation failure duced by the influence of tunnel construction, and the failure always has the characteristics of large deformation, quickly deformation development, long lasting time and the distinctly asymmetry and inhomogeneity in time-space effect. For the same cross section, the periodicity of the surrounding rock deformation with the excavation can be obviously divided to three stage by deformation rate: the sharp deformation stage, the stable deformation stage and the rheological stage. After the excavation of tunnel, the surrounding rock deformation has the distinctly time-space effect, the time effect mainly occurs in the rheological stage, the space effect mainly occurs in the sharp deformation stage, while the stable deformation stage is the transition period between the two above.(4) The loose range of watery weakly consolidated sandstone under the influence of tunnel construction can be confirm by the seismic refraction layer analysis method. This method firstly estimate an initial model by the time field method and the delay time method, based on this model, modeling analysis adopts the minimum travel time tree method, inversion analysis adopts the damping least square method, this paper has calculated the ray path through several times of iteration based on the initial model, the fitter the calculation time-distance curve and the measured curve, the better it is, the best velocity model can be the explanation result. The relaxation zone is the low velocity zone which the surface wave velocity value is less than1000m/s; the loose zone is the gradient zone which the central wave velocity value is between1000m/s and2500m/s; the undisturbed zone is the relative stable zone which the bottom wave velocity value is less than2500m/s; the basis of the boundaries among each zone is the speed gradient and the slide interface position of the wave radiation.(5) Based on the special mechanical properties of Humaling with watery weakly consolidated sandstone, advanced support and reinforcements measures are adopted to avoid the deformation of surrounding rock. Support structures are closed as soon as possible. Tunnel is excavated one block with another by step. And the concept of monitoring measurement is also used. Numerical simulation and engineering analogy method are used to ensure the excavation method of the Humaling tunnel and the construction method of the inclined hole to the tunnel. And also some optimization analysis is conducted.(6) The finite element method is used to analysis the application time of primary liner of the watery weakly consolidated sandstone tunnel. We can conclude that the deformation control of surrounding rock should be the center of construction. The timeliness of primary liner should be emphasized under the premise of the safety of the primary liner. With the field monitoring of the typical section of watery weakly consolidated sandstone tunnel, we can conclude that the pressure between primary liner and rock mass has great time effect. So the design of support should consider the long-term rheological effect. The distribution of pressure presents the heterogeneity in spatial regularities. The contact pressure between primary liner and rock mass increases at first and decreases later, and trend to be stabilize at last. The factors that caused the change include the strength and stiffness variation after the form removal, the compactness of the concrete, stress release after the form removal and also the influence of the shrinkage and creep of the concrete. The contact pressure between the primary and secondary liner is asymmetry. It gradually increased from crown, to spandrel, to haunch, to the top of arch-wall and to the bottom of the arch-wall as a whole. But the measure value is relatively small for the springing and invert of the tunnel.(7) The Humaling tunnel with watery weakly consolidated sandstone has a lower strength, it will be soften with water and has a bad stability, and it also can easily collapse. The tunnel often appears the trouble of sand gushing, water burst, large settlement, the deformation of primary liner, etc. The rock mass has the engineering properties of little particle, water sensitivity and also has the liquidation effect with watery unconsolidated conditions. This article intensively studies the physical and mechanical properties of this kind of ground, and forms the technologies of mild type well point dewatering based and deep negative pressure precipitation on step method. Dual fluid back fracturing grouting technology is adapted based on aquaporin and local plastic clay rock mass. The auxiliary construction technologies help to solve the stability problem of the rock mass and control the deformation of the ground effectively, and also guarantee the project schedule.更多还原