大断面小净距隧道围岩稳定性数值分析 大断面小净距隧道围岩稳定性数值分析

结合小净距隧道工程特点,分别建立不同跨度小净距隧道有限元计算模型,对隧道施工过程力学特征及围岩稳定性进行对比分析,以研究三车道大断面小净距隧道区别于两车道小净距隧道的基本力学特征。分析结果表明,对应不同隧道跨度、隧道净距和围岩级别对隧道施工过程中围岩稳定性的影响有显著差别,相同隧道净距条件下,三车道小净距隧道围岩应力状态比两车道隧道差,净距越小,差别越大,而围岩质量越低,差别也越显著;另外,在质量较差的围岩中,大断面小净距隧道围岩受力最薄弱部位主要集中在岩柱雁形部,而两车道小净距隧道则为岩柱中部。研究结果可为大断面小净距隧道的设计、施工提供有益的参考。     

鹤上大断面小净距隧道施工方案优化分析

结合福州国际机场高速公路鹤上大断面小净距隧道工程实际,建立了大断面小净距隧道施工动态有限元分析程序,对隧道施工方案的优化进行了数值模拟分析。分析中模拟了双侧壁导坑法、中隔壁法和上下台阶法3种施工方案,对拱顶下沉、地表沉降、中间岩柱应力、围岩稳定性等进行了对比分析,并结合鹤上隧道围岩实际情况,在隧道出口Ⅴ级围岩段,改双侧壁导坑法为中隔壁法,顺利完成了施工,对降低施工成本、加快施工进度均起到了较好的作用,研究结果可为类似条件下大断面小净距隧道的设计、施工提供借鉴与参考。     

大断面小净距大帽山隧道现场监控量测及分析

结合大帽山隧道的工程实践,通过围岩内部位移、拱顶沉降、围岩压力和锚杆应力的现场监控量测工作,研究复杂地质条件下大断面小净距隧道双侧壁导坑法施工时围岩的稳定性。阐明分导洞开挖时围岩内部位移的变化趋势、特点及位移场,相邻导洞施工时的相互影响,围岩与支护结构间的相互调整变形机制,拱顶沉降捕捉的变形小于围岩实际变形的原因,支护结构的压力和锚杆应力状态及其与围岩位移的变化关系。监测结果表明,大断面小净距隧道Ⅴ级围岩段的破碎带采用现有的施工工艺和支护参数是可行的,围岩变形可控,支护结构的支护效果显著,围岩基本稳定。研究的方法、分析和结论可为类似条件下隧道工程的设计、施工、监测和进一步的理论研究提供参考和借鉴。     

基于黄土隧道洞口浅埋段的Peck公式修正

黄土隧道洞口施工地表沉降开裂影响施工安全,以往采用Peck公式进行研究,存在预测精度等问题。为更准确地预测黄土隧道洞口浅埋段地表沉降,以临夏-大河家高速公路胡林家隧道为例,基于进口段实测数据,采用线性回归法对Peck公式进行优化。引入最大沉降量S_max修正系数α、降槽宽度i的修正系数β和隧道开挖进尺对最大沉降量影响的系数α₁,确定修正系数得出Peck修正公式。基于洞口浅埋段开挖进尺与最大沉降间的影响关系,发现埋深对S_max修正系数与沉降槽宽度的作用规律,构建黄土隧道洞口浅埋段施工参数对地表沉降关系模型。实测数据样本点分布在修正后的Peck公式上下限之间,修正后的Peck公式误差减少,对临夏等地区黄土隧道洞口浅埋段的适用性较好。     

破碎岩体浅埋大跨公路隧道开挖方案对比研究

三车道高速公路隧道通常跨度较大、高跨比较小属于大跨扁平隧道。这种结构型式对围岩稳定和结构受力均产生不利影响,因此施工中有必要通过开挖方案比选确定合理的开挖方法。江苏省宁波-常州高速公路茅山东隧道为上下行分离式双向6车道浅埋大跨扁平隧道。对于破碎的Ⅳ级围岩,针对设计阶段拟采用CRD法和实际施工采用下断面左右分部台阶法的开挖方案在设计支护条件下的三维数值模拟,从理论上分析了下断面左右分部台阶法是可行的。与实际施工过程的监控量测结果进行对比分析,进一步证实了实际开挖方案的合理性。研究成果可以为同类工程的设计与施工提供理论参考。     

西格二线关角隧道浅埋砂层段施工技术及力学效应研究

关角隧道是西（宁）格（尔木）二线的控制性工程,在隧道入口处存在长约450 m的砂层,施工难度较大。由于在3台阶施工中出现了冒顶事故,故提出了4台阶施工的设想,并利用三维数值计算模拟了4台阶开挖支护过程,揭示了隧道的空间变形、地表沉降和初支受力特征。通过与3台阶施工模拟结果对比证实了4台阶方案的优越性;现场施工和变形量测结果表明,采用大拱脚断面形式和超短四台阶施工方案,施作长大水平超前管棚、设置临时钢横撑、缩短仰拱封闭距离等是保证大断面浅埋砂层隧道安全施工的有效方法,对其他类似工程施工提供了宝贵的工程经验。     

浅埋大跨小净距隧道断面形态及合理间距的优化研究

对于大跨度小净距隧道而言,合理扁平率及双洞间距的设计对于节约成本,提高隧道线型规划具有至关重要的作用,因此,优化大跨度小净距隧道的扁平率及其间距是隧道设计施工面临的关键问题。利用大型有限元分析软件ABAQUS的标准设计语言Python编程,对某拟建大跨度小净距隧道不同扁平率及其间距进行参数化设计;采用精确罚函数法以及Nelder-Mead优化算法相结合的有限元优化分析计算程序,以隧道开挖面积、围岩塑性区、地表沉降和拱顶下沉等作为优化目标值,对建立的参数化模型进行计算,提出依托工程条件下扁平率及间距的最优组合。研究方法和成果对推动大断面小净距隧道的发展和应用具有重要的现实意义。     

The Investigation of Twin Tunnel Stability: Effect of Spacing and Diameter

The underground excavation became the backbone of developing as well as developed country due to unavailability of surface area and increase demand of space for transportation, water channeling, waste disposal and storage. Except for transportation, the crystalline rocks (high strength, low porosity and less permeability) are considered most suitable and safe space for the storage of radioactive waste as well as petroleum. The role of spacing between twin tunnel and tunnel’s diameter in its stability was carried out using finite element method. Not much research has been done on twin tunnel spacing in hard rock. In the present study, a total of ninety simulations were performed to investigate critical spacing of the twin tunnel in granitic rock mass. Twin tunnel diameter is varied from the 2 m to 10 m and their spacing varied from 0.2 to 2 times of diameter. It was concluded that minimum spacing should be 0.8 times of the tunnel diameter. It was also found that small diameter tunnel effects only near field but large diameter tunnel effect near field as well as far field. The vertical hole, approximately 3m diameter, containing radioactive waste canister should be drilled at the interval of more than 2.4m.     

Monitoring of Three-dimensional Additional Stress and Strain in Shield Segments of Former Tunnels in the Construction of Closely-Spaced Twin Tunnels

In recent years, with the development of urbanization, the construction of closely-spaced twin tunnels is becoming more and more common. How to ensure the safety of the former tunnel during the construction of the later tunnel has become the focus of the construction of closely-spaced twin tunnels. To study the safety of the former tunnel segment structure, this paper analyzed the field monitoring data of practical engineering (the section with the minimum separation (4.5 m) between the twin tunnels from Anyuanxi station to Chunshenhu station on the Suzhou Metro Line 4 in Jiangsu, China) and obtained the dynamic change law of additional stress and strain of the former tunnel segment under the influence of the construction of later tunnel. Based on this research, the following conclusions were drawn: (1) The maximum circumferential tensile stress on the segmental structures was shown to be 2.62 MPa at the horizontal position on Section S2 in the side adjacent to the later tunnel, which should be main monitored. (2) The maximum values of the vertical deformation and peripheral convergence of the segments were 16.21 and 17.39 mm, separately, both of which were less than two-thirds of the allowable deformation. Therefore, the shield tunnel deformations were within allowable limits. This research results can provide guidance for similar engineering.     

Dynamic Response of Shallow-Buried Small Spacing Tunnel with Asymmetrical Pressure: Shaking Table Testing and Numerical Simulation

A series of shaking table tests were designed and carried out to study the seismic behaviors of a shallow-buried small spacing tunnel with asymmetrical pressure. The key details to shaking table model test, including test equipment, model similarity relation, similarity constant, model box, physical model, layout of transducers, seismic waves, and loading system were presented. The numerical simulation of the shaking table test was also carried out by using a finite element simulation software. The results show that: (1) the Fourier spectrums in the vertical direction and horizontal direction are different at the same measuring point. The structure of tunnel transforms the Fourier spectrum of horizontal direction. (2) The stability of middle rock pillar is poor under seismic wave action. The anchor plays an important role in strengthening the stability of middle rock pillar. The dynamic strain of anchor has accumulative effect. (3) The numerical simulation results are in significant agreement with the shaking table test results. (4) Compared with type of seismic wave, peak seismic wave has a significant effect on acceleration response of tunnel. The peak acceleration response of the tunnel is linear with the peak seismic wave, in the horizontal direction. The peak acceleration response is nonlinear in the vertical direction. (5) The axial force of cross section at arch foot is larger than other position. The shock absorption effect of 10 cm seismic isolation layer is better than 5 and 20 cm.     

市政道路工程勘察资料的时效性分析和探讨

城市化的发展,使市政道路改造工程越来越多,如何科学有效地利用拟建期的勘察资料,节约勘察成本,成为工程勘察关注的焦点。通过对场地地形地貌和地质构造、地层和水文地质条件、岩土物理力学性质、场地稳定性评价和地震效应、岩土工程重点分析评价等岩土工程要素进行分析,对比前后各要素,探讨勘察资料的时效性,进而确定勘察点布置和深度,以及取土（水）样和原位测试工作量。最后以具体工程为例,探讨勘察要点,指出利用拟建期的勘察资料应主要考虑4.0m以内的地层变化,重点勘察路基破损的路段。     

围岩监控量测技术在浅埋大断面公路隧道中的应用

以安楚公路２、３号隧道围岩监测资料为基础，以进出口边玻和Ｋ７５＋４２０～Ｋ７５＋４３０段作为实例，介绍了应用监测技术提供的围岩变形信息来指导施工、确保安全的情况。     

特大跨度小净距隧道中间岩柱可靠度分析及其加固处理措施

魁岐2号隧道位于福卅I国际机场高速公路二期工程A3标段,隧道跨度达到19．9m,中间岩柱最小净距为11．7m,为国内首座双向八车道小净距隧道工程。针对魁岐2号隧道工程的特殊性,利用离散单元法对节理岩体中特大断面小净距隧道的受力情况进行了分析,根据可靠度理论,通过对魁岐2号特大断面小净距隧道中间岩柱的可靠性分析发现,对于特大断面小净距隧道,中间岩柱最薄弱的部位主要集中在岩柱上部,因此,埘于特大断面小净距隧道施工过程中宜重点对岩柱上部进行加固处理。同时,根据不同围岩级别中中间岩柱的可靠度值显示,魁岐2号特大断面小净距隧道的净距取值基本上是合理的,整体上二能满足稳定性的要求。     

小浪底工程导流洞大洞径固结灌浆施工台车的设计与运行

小浪底导流洞洞径为１４．５ｍ,钻灌台车以同心齿圈方案解决了钻孔问题,并配以灵活的轨道系统,为大洞径钻灌施工提供了成功的范例。     

Chemical composition of planetary nebulae in the Large and Small Magellanic Clouds

The technique of nebular-gas diagnostics was used to find electronic temperatures T _e , concentrations n _e , relative ion concentrations n(A⁺ⁱ )/n(H⁺), and chemical abundances A/H for planetary nebulae in the Large and Small Magellanic Clouds. This analysis took into account inhomogeneities of the nebular-gas density in the nebulae. We determined the pre-galactic helium abundance Y _p and its rate of enrichment dY/dZ for the envelopes of nine nebulae in the Large Magellanic Cloud. Taken together with the Galaxy’s planetary nebulae and HII regions in blue compact dwarf galaxies, Y _p = 0.248 ± 0.002, dY/dZ = 2.31 ± 0.48 and Y _p = 0.247 ± 0.002, dY/dZ = 3.03 ± 0.56, respectively, when macroinhomogeneities and macro/microinhomogeneities of the gas density in galactic nebulae are taken into account.     

罗定—岑溪公路G324线砼路面沉降复位加固试验

介绍了循环－纯压法相结合灌浆复位加固法和双液法灌浆复位加固法在罗定－岑溪公路路基沉降复位加固中的试验情况，并对二者进行了比较。     

Research on Creep Deformation and Control Mechanism of Weak Surrounding Rock in Super Large Section Tunnel

Geotechnical and Geological Engineering - In order to solve the difficulties of creep deformation of surrounding rock in super large section tunnel, taking Letuan tunnel of Binlai expressway, a...