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1.
考虑累积损伤效应的围岩变形特性研究 总被引：1，自引：0，他引：1
隧道爆破开挖诱发的动力扰动作用范围往往远大于其开挖进尺,同一部位围岩受到循环爆破开挖的多次扰动普遍存在累积损伤。对乌东德水电站左岸导流洞爆破开挖过程中的爆破振动和围岩变形监测进行了监测和数值分析,基于累积损伤理论,通过引入损伤判据及损伤变量,考虑计算中产生的不同程度的损伤区域的岩体参数劣化,并将劣化后的参数引入相应损伤单元进行后续开挖爆破数值模拟计算,从而对岩体爆破开挖累积损伤效应进行模拟。通过比较乌东德水电站导流洞的实测数据以及数值模拟计算结果发现,考虑累积损伤的计算结果无论是爆破振动速度还是围岩变形均更接近于实测值。对爆破开挖的分析模拟中应考虑围岩的多次循环爆破累积损伤效应。 相似文献
2.
高地应力条件下隧道或硐室钻爆开挖需考虑初始地应力动态卸荷效应,同时其最终损伤形态会受多个因素影响。采用三维有限差分软件FLAC3D讨论了爆破荷载与地应力动态卸荷复合作用下隧道围岩损伤分布,并重点研究了侧压力系数、岩体力学性质、卸荷速率对围岩损伤范围的影响,最后通过赣龙铁路梅花山隧道开挖损伤区检测结果进行了验证。研究表明,考虑动态卸荷效应的围岩损伤范围明显大于只考虑爆破荷载作用下的围岩损伤范围,在中高地应力条件下,初始地应力动态卸荷对围岩的损伤破坏作用不可忽视;随着侧压力系数逐渐增大,损伤区形态呈现明显的方向性,当侧压力系数为1时,损伤区沿开挖轮廓面分布较为均匀,侧压力系数不为1时,损伤区主要向小主应力方向集中;岩石力学性质越好,损伤范围越小;卸荷速率越快,围岩损伤范围越大,但影响并不十分显著。结果可为高地应力下隧道开挖稳定性分析和支护设计提供一定参考。 相似文献
3.
为预估和控制爆破荷载作用下围岩损伤范围,在赣龙铁路梅花山隧道工程现场进行岩体声波测试,得到围岩的损伤范围。根据爆破荷载作用下岩体损伤发展规律,采用基于概率形式的损伤变量定义,运用三维有限差分软件对不同地应力状态下爆破产生的围岩损伤范围进行数值模拟,并与现场岩体声波测试结果进行比较。计算结果表明,数值计算与实测结果有较好的一致性,随着地应力大小增大,围岩损伤范围呈现先减小后增大的趋势,且增大幅度较大,地应力较高时,局部部位如顶板、底板损伤更为明显,说明地应力大小对围岩损伤分布有着显著影响;随着侧压力系数增大,损伤范围先减小后增大,但增速逐渐减小。所得到的结论可为高地应力下隧道稳定性分析和支护设计提供依据。 相似文献
4.
Elastic Solution for Deep Tunnels. Application to Excavation Damage Zone and Rockbolt Support 总被引：1，自引：1，他引：0
A. Bobet 《Rock Mechanics and Rock Engineering》2009,42(2):147-174
Summary A new formulation is presented for deep circular tunnels in rock with cylindrical anisotropy. The formulation is an exact
solution since it satisfies equilibrium, strain compatibility, and the anisotropic constitutive model. Complete solutions
have been found for two scenarios: tunnel with excavation damage zone, and tunnel with rockbolt support. The solution is based
on the assumption of a deep, circular tunnel in a medium with two homogeneous zones: an inner zone surrounding the tunnel,
which is either isotropic or anisotropic, and an outer zone, for the remainder of the medium, which is isotropic. Plane strain
conditions, elastic response of rock, rockbolts and support, and simultaneous excavation and support installation are also
assumed. For tunnels surrounded by an excavation damage zone with reduced rock properties, the tangential stresses and the
radial deformations at the tunnel wall are very sensitive to both the magnitude of stiffness reduction of the damaged rock
and the size of the damaged zone. The effect of the rockbolts on the rock is approximated by treating the rockbolt-rock composite
as a material with cylindrical anisotropy with stiffnesses related to the properties of the rock and rockbolts, and spacing
of the rockbolts. Comparisons between the analytical solution and a numerical method show small differences and provide confidence
in the approach suggested. 相似文献
5.
Effect of Blast-Induced Vibration from New Railway Tunnel on Existing Adjacent Railway Tunnel in Xinjiang, China 总被引：1，自引：1，他引：0
The vibrations of existing service tunnels induced by blast-excavation of adjacent tunnels have attracted much attention from both academics and engineers during recent decades in China. The blasting vibration velocity (BVV) is the most widely used controlling index for in situ monitoring and safety assessment of existing lining structures. Although numerous in situ tests and simulations had been carried out to investigate blast-induced vibrations of existing tunnels due to excavation of new tunnels (mostly by bench excavation method), research on the overall dynamical response of existing service tunnels in terms of not only BVV but also stress/strain seemed limited for new tunnels excavated by the full-section blasting method. In this paper, the impacts of blast-induced vibrations from a new tunnel on an existing railway tunnel in Xinjiang, China were comprehensively investigated by using laboratory tests, in situ monitoring and numerical simulations. The measured data from laboratory tests and in situ monitoring were used to determine the parameters needed for numerical simulations, and were compared with the calculated results. Based on the results from in situ monitoring and numerical simulations, which were consistent with each other, the original blasting design and corresponding parameters were adjusted to reduce the maximum BVV, which proved to be effective and safe. The effect of both the static stress before blasting vibrations and the dynamic stress induced by blasting on the total stresses in the existing tunnel lining is also discussed. The methods and related results presented could be applied in projects with similar ground and distance between old and new tunnels if the new tunnel is to be excavated by the full-section blasting method. 相似文献
6.
软岩浅埋隧道施工工法比选 总被引：2，自引：0，他引：2
目前在高速公路软岩浅埋隧道施工中均不同程度地出现了围岩坍塌、地表产生大面积沉降等问题。广福隧道某浅埋段,地质条件复杂,断面大、岩性差,受构造影响比较严重,而且顶板厚度比较薄,易发生坍塌、冒顶现象。为确保浅埋段隧道的施工安全,尽量减少隧道开挖引起的地层沉降和围岩变形,采用FLAC3D对4种施工工法全断面法、短台阶法、单侧壁导坑法和双侧壁导坑法进行模拟,分析了4种工法下地表沉降、隧道围岩周边位移和塑性区的变化特点,选出一种技术可行、经济合理的施工工法,得出一些有意义的结论。 相似文献
7.
Analytical stress and displacement due to twin tunneling in an elastic semi‐infinite ground subjected to surcharge loads 
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下载免费PDF全文 The construction of twin tunnels at shallow depth has become increasingly common in urban areas. In general, twin tunnels are usually near each other, in which the interaction between tunnels is too significant to be ignored on their stability. The equivalent arbitrarily distributed loads imposed on ground surface were considered in this study, and a new analytical approach was provided to efficiently predict the elastic stresses and displacements around the twin tunnels. The interaction between 2 tunnels of different radii with various arrangements was taken into account in the analysis. We used the Schwartz alternating method in this study to reduce the twin‐tunnel problem to a series of problems where only 1 tunnel was contained in half‐plane. The convergent and highly accurate analytical solutions were achieved by superposing the solutions of the reduced single‐tunnel problems. The analytical solutions were then verified by the good agreement between analytical and numerical results. Furthermore, by the comparison on initial plastic zone and surface settlement between analytical solution and numerical/measured results of elastoplastic cases, it was proven that the analytical solution can accurately predict the initial plastic zone and its propagation direction and can qualitatively provide the reliable ground settlements. A parametric study was finally performed to investigate the influence of locations of surcharge load and the tunnel arrangement on the ground stresses and displacements. The new solution proposed in this study provides an insight into the interaction of shallow twin tunnels under surcharge loads, and it can be used as an alternative approach for the preliminary design of future shallow tunnels excavated in rock or medium/stiff clay. 相似文献
8.
Analytical and Numerical Study of the Mechanics of Rockbolt Reinforcement around Tunnels in Rock Masses 总被引：1，自引：0，他引：1
C. Carranza-Torres 《Rock Mechanics and Rock Engineering》2009,42(2):175-228
Summary This paper addresses the problem of quantifying the mechanical contribution of rockbolts installed systematically around tunnels
excavated in rock masses. The mechanical contribution referred to here is that of increased stress confinement and decreased
tunnel convergences as compared with corresponding stresses and displacements obtained for non-reinforced tunnels. The problem
is treated analytically first by presenting a closed-form solution for stress and displacement distributions around a circular
tunnel excavated in elastic material and reinforced by grouted or anchored rockbolts. The analytical solution assumes that
rockbolts are regularly spaced around the tunnel and that axi-symmetry conditions of geometry and loading apply. The results
obtained with the closed-form solution are shown to be equivalent to the results of the same problem solved with traditional
numerical methods. Based on the analytical and numerical results and by introducing dimensionless ratios that allow to quantify
the increase of radial stresses and the decrease of radial displacements in the reinforced region of the tunnel, the paper
shows that reinforcement can have a significant mechanical effect (i.e., increasing the confinement and decreasing the convergences)
in tunnels excavated in rock masses of poor to very poor quality. The paper analyzes then the mechanical contribution of rockbolt
reinforcement when the rock mass is assumed to behave elasto-plastically. For this case, it is shown that rockbolt reinforcement
can also have a critical effect in controlling the extent of the plastic failure zone and the convergences of the tunnel.
Correspondence: C. Carranza-Torres, Department of Civil Engineering, University of Minnesota, Duluth Campus, 1305 Ordean Court,
Duluth, USA 相似文献
9.
锦屏二级水电站引水隧洞爆破开挖损伤特性研究 总被引：1，自引：0，他引：1
爆破开挖导致的围岩损伤是围岩稳定性的重要影响因素。采用数值分析及现场检测的方法研究了锦屏二级引水隧洞岩体爆破开挖损伤特性。数值模拟结果表明,引水隧洞开挖引起的围岩应力重分布是围岩损伤的主要原因,爆炸荷载和应力重分布的耦合作用将增大引水隧洞围岩损伤区范围,增大的损伤深度可达1.5 m,考虑开挖荷载瞬态卸荷动态损伤效应的损伤区范围最大,较单独考虑围岩地应力准静态重分布所导致的损伤深度可增大1.9 m,平均损伤深度增大近1倍。现场检测成果较好地验证了数值模拟结果,表明爆破开挖可显著增大围岩的损伤范围。锦屏二级水电站引水隧洞开挖过程中,不可忽视爆炸荷载及开挖瞬态卸荷对围岩的损伤作用。 相似文献
10.
V. M. S. R. Murthy Kaushik Dey 《Fragblast: International Journal for Blasting and Fragmentation》2003,7(3):149-166
Tunnels are required to be constructed for meeting different human needs such as power generation, transportation, underground storage, sewage etc. The predominant method of excavation, world over, is drilling and blasting owing to its capability to meet changing geo-technical conditions. Irrespective of the purpose for which the tunnels are driven, all are plagued by overbreak problems. Tunnels driven for water conveyance in hydroelectric power projects, in particular, need to be excavated with minimum overbreak to minimise cost of permanent concrete lining. Thus, predicting overbreak assumes significant importance to design site-specific blasts for minimizing rock damage. This paper presents a brief review of existing PPV (Peak Particle Velocity) based blast-induced rock damage estimation criteria and attempts to outline the ground vibration threshold levels for overbreak/rock damage in a tunnel driven through compact basalt. Rock damage manifested as overbreak is measured and correlated with the possible threshold levels of PPV. Also, the PPV levels for crack initiation and widening are proposed. The case pertains to a lake tap horizontal tunnel of Koyna Hydro-electric Power Project, India which is a water feeder tunnel for a fully underground hydroelectric power project. The tunnel was driven under a shallow rock cover of average depth ranging from 20 to 25m beneath a fully charged water body. The parting rock is mainly compact basalt. Blasting was carried out in two rounds in a controlled manner, i.e., by limiting the maximum charge per delay based on ground vibration monitoring. Ground vibration generated with free face (in second round) has been modeled and a new ground vibration propagation equation is proposed for tunnel blasting including the effect of an extra free face. The threshold limits of PPV for different degrees of overbreak/rock damage are proposed from extrapolated vibration predictor equation. The actual overbreak in the tunnel, measured using a Planimeter, varied from 2.45 per cent to 17.75 per cent of the finished tunnel area. The predicted overbreak from extrapolated PPV measurements is compared against the measured overbreak to validate the proposed blast-induced rock damage (BIRD) assessment model. The PPV level for overbreak was found to exceed 2050 mm/s in compact basalt. A linear relationship between the overbreak and maximum charge per delay is also established to design a tunnel blast in similar formations. 相似文献
11.
考虑隧洞瞬态开挖卸载并分析围岩的动态响应对研究其变形破坏机制非常重要。在静水压力圆形隧洞动态卸荷模型理论分析的基础上,采用FLAC3D的Fish语言开发了隧洞开挖动态卸载围岩响应模拟计算程序。验证算例模拟结果与理论结果对比,证明了程序的正确性,围岩的应力变化和体积应变增量均呈现由表及里的波浪型变化,能较好地模拟围岩的动态卸荷响应。根据Griffith强度准则计算得到的不同时刻围岩的损伤范围表明,考虑动态卸载时围岩的损伤区比采用静态分析要大。采用该程序分别模拟了不同卸载时间、卸载路径、隧洞形状、隧洞直径、地应力等条件下,隧洞动态卸载围岩的动态响应。结果表明,在卸载时间变短、先慢后快卸载路径、洞形为方形、洞径变大和地应力差值增大的条件下,隧道围岩内最大、最小主应力应力差也增大。深部隧洞采用瞬态卸载分析对于深入研究围岩变形破坏机制具有重要意义。 相似文献
12.
Groundwater Effect on Faulted Rock Mass: An Evaluation of Modi Khola Pressure Tunnel in the Nepal Himalaya 总被引：1，自引：0，他引：1
Groundwater has a negative impact not only in construction activity, but also in stability of a tunnel. Severity increases particularly in tunnels passing through fault gouge and breccia, where rock material is completely crushed and extremely weak. Instantaneous collapse and excessive plastic deformation is most likely in tunnels passing through such zones. Often, ‘flowing’ conditions may prevail if groundwater is mixed in the rock mass. This paper presents one such tunnel case in the Nepal Himalaya; i.e. the Modi pressure tunnel. This pressure tunnel passes through a tectonic fault consisting of gouge material. High deformation in the tunnel was observed while excavating the tunnel through the fault. Based on the tunnel deformation that was actually measured, the paper first back-calculates the rock mass strength by analytical approach. Then, the extent of in-situ stress condition in the area is determined by numerical modeling for the rock mass with no ground water in consideration. The ground water effect is then analyzed. We found that the effect of ground water with a static head <1.5 bar pressure may increase the deformation by up to a maximum of 30 %. Finally, we briefly discuss uncertainties related to the input parameter study and used methodologies. 相似文献
13.
Yan Xing P. H. S. W. Kulatilake L. A. Sandbak 《Geotechnical and Geological Engineering》2017,35(1):45-67
Stability and deformation of rock masses around tunnels in underground mines play significant roles on the safety and efficient exploitation of the ore body. Therefore, understanding of geomechanical behavior around underground excavations is important and necessary. In this study, a three-dimensional numerical model was built and stress analyses were performed by using 3DEC software for an underground mine in USA using the available information on stratigraphy, geological structures and mechanical properties of rock masses and discontinuities. Investigations were conducted to study the effect of the lateral stress ratio (K0), material constitutive models, boundary conditions and rock support system on the stability of rock masses around the tunnels. Results of the stress, displacement, failure zone, accumulated plastic shear strain and post-failure cohesion distributions were obtained for these cases. Finally, comparisons of the deformation were made between the field deformation measurements and numerical simulations. 相似文献
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15.
深埋长隧道TBM施工关键问题探讨 总被引：2，自引：0，他引：2
针对深埋长隧道开挖所面临的高水压、高地压、高地温、大变形、难支护等问题,分析总结传统钻爆法开挖与支护技术、全断面隧道掘进机（TBM）施工技术、TBM导洞扩挖技术应用中的优劣,TBM导洞扩挖法为深埋长隧道开挖提供了新的设计思路。由于深埋长隧道的建设环境与浅埋隧道建设环境存在显著差异,TBM施工将面临3个关键问题--岩爆问题、卡盾（大变形）问题和未准确探测前方地质而发生的施工事故（涌水、突泥等）。为揭示TBM施工过程中卡盾的存在性,分别针对某一特定地质条件下深埋软、硬岩TBM施工进行理论分析和数值模拟研究。结果表明,软岩地层TBM施工发生卡盾,而硬岩完整地层TBM施工未发生卡盾。 相似文献
16.
岩爆是深部高地应力区地下岩体工程中的主要工程地质灾害之一,其发生及烈度预测是一个复杂的不确定系统问题。为了有效预测和判别深部工程岩爆灾害,在总体考虑岩爆各影响因素的基础上,选取地下工程中岩体完整性指数、岩石单轴抗压强度、岩石单轴抗拉强度、围岩最大切向应力、围岩抗压强度与其抗拉强度的比值、围岩切向应力与围岩抗压强度比值、弹性能量指数、岩爆倾向性指数作为岩爆预测的评判指标,提出了一种基于非线性参数优化的RBF-AR岩爆预测模型。在终南山隧道竖井岩爆判别中,利用RBF-AR法进行计算,计算结果与实际情况完全一致,表明该模型在岩爆预测中的可行性和有效性。 相似文献
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18.
损伤条件下深部岩体巷道光面爆破参数研究 总被引：3，自引：0，他引：3
岩体条件复杂多变,为了提高光面爆破的适应性、改善光面爆破效果,对损伤条件下深部岩体巷道光面爆破参数进行研究。通过对深部岩体巷道光爆层原岩应力场、光面爆破机制和振动损伤特征进行分析,基于爆炸应力波和爆生气体综合作用理论,考虑高原岩应力和岩石损伤影响,提出了损伤条件下深部岩体巷道光面爆破参数确定的计算方法。研究表明, （1）高原岩应力相当于提高了岩石的抗拉强度,不利于炮孔初始裂纹的形成及贯通,宜减小周边眼间距;（2）岩石损伤后,其他条件不变,光面爆破的炮孔间距和抵抗线值可适当加大;（3）高原岩应力和损伤条件下,光面爆破的炮孔间距较小时,容易造成爆后围岩损伤,降低围岩的稳定性能,因此,提高爆破效果的同时应及时加强支护,以确保施工安全和围岩稳定;（4）本文提出的光面爆破参数计算公式,经现场爆破验证效果良好,适用于复杂多变的岩体环境。 相似文献
19.
采用模型试验和数值模拟方法,研究单轴压缩载荷下带裂纹直墙拱形隧道在不同的裂纹面与隧道垂直边墙之间的夹角 时围岩损伤破坏规律。试验采用水泥砂浆制作成具有不同夹角 的直墙拱形隧道模型,养护30 d后进行加载。数值模拟采用混凝土损伤塑性模型,计算出隧道周边各点的应力和裂纹尖端的应力强度因子,与模型试验结果吻合较好。结果表明,拱肩处的裂纹会降低隧道的整体稳定性及强度,在裂纹尖端及侧壁产生很大的应力集中,但随着 角度的变化,强度降低的程度有所不同;当 = 60?和 = 130?时,裂纹对其整体稳定性及强度的影响最大,其裂纹尖端的应力集中现象最为明显,而且破坏应力峰值仅为无裂纹模型的40.9%和41.8%。 相似文献
20.
Time-dependent response of deep tunnels is studied considering the progressive degradation of the mechanical properties of the rock mass. The constitutive model is based on a rock-aging law for the uniaxial strength of the rock and for the Young’s modulus. A semi-analytical solution is developed for the stresses and displacements around a deep circular tunnel taking into account the face advance. The evolution of the plastic and damage zones over time is determined. Numerical examples are presented for the case of Saint-Martin-La-Porte access adit in France of the Lyon–Turin Base Tunnel. The computed results which are compared with the field data in terms of the convergence of tunnel wall and of the displacements inside the rock mass monitored by multi-point extensometers show the efficiency of the approach to simulate the time-dependent deformation of a tunnel excavated in squeezing ground. Simple relationships are proposed to evaluate the parameters of the constitutive model directly from those of the empirical convergence law presented in previous work. 相似文献