共查询到20条相似文献，搜索用时 250 毫秒
1.
为分析软弱黄土隧道的变形规律,以西宁过境高速大有山黄土隧道为依托,采用精密水准仪和收敛计对隧道地表下沉、拱顶下沉和水平收敛进行了系统现场测试。结果表明：软弱黄土隧道拱顶下沉远大于水平收敛,变形时间长,变形量大,累计拱顶下沉值最大为950.6 mm。在临界埋深范围,围岩变形比深埋、浅埋时都大,且变形量离散性高;围岩变形速率在二衬施作时较大,软弱黄土隧道中作为围岩-支护系统稳定性判据的变形速率宜适当提高;围岩变形随时间变化符合指数函数规律,可利用指数函数预测围岩的最终变形;软弱黄土隧道变形分为急剧变形、持续增长和缓慢增长3个阶段,最终趋于稳定。隧道断面的初次开挖对地表变形影响显著,隧道轴线沉降最大,并沿横向逐渐减小。软弱黄土隧道预留变形量在不同位置处不宜统一设置,西宁地区软弱黄土Ⅴ级围岩建议拱顶预留700～800 mm,边墙预留300～350 mm,拱顶与边墙之间以曲线过渡。 相似文献
2.
为研究湿陷性黄土隧道施工期间的变形特征,本文依托甘肃省某黄土隧道新建工程,综合采用现场实测数据分析和数值模拟开展黄土隧道的变形特征研究。结果表明：(1)隧洞拱顶位移变化速率和累计沉降值最大,且出口右线的沉降速率比左线的更大。与出口相比,进口处的地面沉降值明显较小,其中进口处地面的最大沉降值为35 mm,出口处地面最大沉降为70 mm;(2)建立数值有限元模型进行计算表明,数值模拟结果与实际监测规律基本一致,其中实测隧道开挖结束的拱顶最大沉降为60 mm,而数值模拟结果为78 mm,两者相对误差在20%以内;随着隧道的开挖,隧道应力发生重分布,衬砌两侧发生应力集中,最大值为6.0 MPa,顶部围岩应力达到2MPa。 相似文献
3.
以四川某隧道为研究对象,结合现场地质调研、空心包体地应力测试、初支与围岩接触压力监测等分析手段,对初期支护变形破坏的原因进行分析。分析结果表明:初支变形破坏主要是由地表水下渗、不利地应力条件、地层岩性等因素造成。同时采用FLAC3D,分析开挖后隧道上部粉砂质泥岩夹层对拱顶变形的影响,以及中空锚杆注浆前后初支受力变形情况。模拟结果表明:最大竖向位移及压应力出现在拱顶区域,且位移随着夹层距离的增加而减小,在6.5 m时出现陡降,最大水平位移在右拱腰处;锚杆注浆后拱顶位移减小约10%,边墙位移减少约4%。本文可为类似工程变形破坏原因分析及施工处治方法选择方面提供参考。 相似文献
4.
在隧道施工前,应用数值模拟分析的方法,分析浅埋砂质黄土隧道施工力学效应和变形特征。根据浅埋砂质风积黄土隧道在施工过程中地表沉降量大和洞内施工安全风险大等特点,结合隧道实际监测数据,反演计算得到侵限段地质力学参数,为迈式管棚超前支护及径向迈式锚杆的全施工过程数值模拟提供计算依据,为控制隧道围岩变形提供数据支撑。计算结果显示,隧道侵限段地表最大沉降11.4 mm、最大拱顶下沉30.4 mm、最大水平收敛48.5 mm,隧道整体变形量减小,迈式管棚超前支护可以有效地提供纵向支撑,承受侵限土体压力、约束围岩变形和控制地表沉降,同时为支护侵限段钢拱架的安全拆换提供保障。研究结果表明:径向迈式锚杆、迈式管棚超前支护、环形支撑钢拱架和锁脚锚杆一起,构成了浅埋风积砂质黄土隧道主被动变形综合控制体系,有效地解决了浅埋风积砂质黄土隧道软弱围岩超前支护的难题。 相似文献
5.
以某黄土公路隧道工程为依托,借助现场测试方法研究浅埋洞口段黄土公路隧道地表沉降、拱顶下沉和周边收敛时态分布规律,并结合实测数据建立隧道施工变形统计分析预测模型。研究结果表明:（1）黄土隧道施工变形呈现显著的时间和空间效应,其时态分布曲线符合指数函数型发展规律;（2）地表沉降随时间呈增长趋势,约60 d后逐渐趋于稳定,其最大值（wmax）的统计变化范围为（?30.78～?105.20）mm;（3）横向地表沉降曲线分布呈凹槽形,沉降槽宽度约（3～5）倍隧道跨度（B）,且隧道开挖引起的地层损失率为0.74%～3.08%;（4）拱顶下沉与周边收敛时态曲线可分为线性增长、持续变形和平稳发展3个阶段,且线性增长阶段占总变形量的60%以上;（5）vmax的统计值变化范围为（?17.1～?201.1）mm,其95%置信区间为[?51.53,?65.11],umax的统计值变化范围为（?12.1～?122.0）mm,其95%置信区间为[?35.08,?43.39],建议V级围岩黄土隧道预留变形量取值范围为（?100～?150）mm;（6）拱顶下沉与周边收敛速率时态曲线呈先急剧增加后逐渐衰减趋势,最终稳定后的拱顶下沉速率（Δv）和周边收敛速率（Δu）依次为（?0.05～?0.80）mm/d和（?0.02～?0.60）mm/d。 相似文献
6.
浅埋偏压连拱隧道施工的力学响应分析 总被引：1，自引：0，他引：1
以江西某高速公路一浅埋偏压连拱隧道为背景,用MARC有限元程序对其出口段进行了动态施工的三维数值模拟。系统研究了塑性区分布和发展、拱顶下沉、正应力与剪应力的集中和转移、中隔墙竖向应力随施工过程的变化规律。研究表明:1.非对称开挖是引起中墙偏压的最关键因素,初衬和二衬的施作对改善中墙偏压作用不大,对称开挖才是最有效途径;2.在浅埋条件下,拱顶下沉有随埋深增大而增大的趋势,位移释放在开挖完成、支护之前就已经大部分完成。3.左右洞上台阶开挖后拱顶出现拉应力区,是易坍方部位,应超前或及时支护;4.由于偏压作用,山脊一侧边墙和中墙墙踵处塑性区更发育,该侧更易失稳;5.施工完毕,隧道两侧边墙附近集中的压应力转移到二衬和仰拱上,使二者成为应力集中部位,从而改善了隧道围岩的受力状况。 相似文献
7.
以某水电站地下厂房工程为实例,采用数值分析方法,通过对比厂房洞室群是否施加系统锚杆的差别,获得系统锚杆对洞室群稳定性的影响.结果表明,施加系统锚杆对围岩主应力影响小,但能平均降低围岩位移28.07％,降低拱顶和拱角处围岩位移34％以上,降低主厂房和尾闸室边墙塑性破坏区深度2.2～4.8m,在一定程度上提高洞室群的整体稳... 相似文献
8.
高边墙围岩稳定是超大型地下洞室施工期关注的重点。基于工程监测资料,探究了白鹤滩水电站左岸地下厂房高边墙围岩变形演化分布规律及破坏机制。研究表明：在垂直方向上,开挖面距离在10 m范围内边墙卸荷响应强烈,该阶段围岩变形约占总变形量的50%～55%;在洞轴方向上,开挖影响集中在2倍洞跨范围内,该区域内变形约占总变形量的97%;在结构面发育部位前后围岩变形的分异量较大,且由于软弱夹层的柔塑性,围压解除后错动带应变能释放是一个缓慢的过程,时效剪切特征明显;发掘并总结逐层下挖过程中高边墙围岩应力状态的演化规律,并划分为应变能积聚、释放、应力调整及趋稳4个阶段。该研究成果可为工程支护设计提供一定支撑,并供同类工程参考。 相似文献
9.
大断面小净距大帽山隧道现场监控量测及分析 总被引：10，自引：0，他引：10
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。 相似文献
10.
采矿巷道围岩变形机制数值模拟研究 总被引：6，自引：0，他引：6
研究了大冶铁矿龙洞-62 m、-74 m水平采矿巷道开挖后的二次应力分布及巷道变形机制。首先根据现场工程地质勘查和室内岩石力学试验对巷道围岩进行了工程地质分组和岩石力学参数确定;在此基础上运用FLAC3D数值模拟软件研究了巷道开挖后的应力应变状态,分析了围岩变形机制;并根据-74 m水平采矿巷道的收敛监测数据对比验证了数值模拟结果。研究结果表明,围岩条件不同的采矿巷道其二次应力分布影响范围有所差异,但围岩主应力总体上表现为由巷道边墙中下部位的压应力集中带逐步过渡到拱顶、底板一定范围内的拉应力集中带。 相似文献
11.
The deformation matrix and the deformation ellipsoid 总被引：1，自引：0，他引：1
Derek Flinn 《Journal of Structural Geology》1979,1(4):299-307
Homogeneous strain can be computed most easily by the methods of matrix algebra. Lines, planes and ellipsoids represented in matrix form can be homogeneously deformed by simple matrix multiplication by linear transformation matrices, the elements of which are the coefficients of the transformation equations. Deformation matrices or linear transformation matrices which cause geological-type homogeneous strain are divided into four classes based on the presence or absence of symmetry and/or orthogonality. The nature of the homogeneous strain caused by each class of deformation matrix is examined. Orthogonal-symmetrical and orthogonal matrices cause rotation. Symmetrical matrices cause irrotational strain with co-axial strain as a special case. Matrices which are neither orthogonal nor symmetrical cause many different types of rotational strain, some of which are examined. 相似文献
12.
传统的非连续变形分析法（DDA）法采用简单的线性位移模式计算效率高,描述大块体的高阶多项式位移模式在一定程度保留了该特点,并提高了计算精度。近年来流行的耦合有限元、自然单元的DDA法实质上是引入相应的插值形函数构成块体位移函数,计算相对低效,但具有计算更精细、更容易施加边界条件等优点。为结合传统DDA法与DDA耦合法各自的优点,建立了一种同时利用传统DDA法线性位移模式与耦合型DDA法非线性位移模式的混合法。该方法非线性模式主要针对大块体,采用了自然单元插值,缘于其具有一定无网格特征,且效率比有限元高。建立了混合模式下的整体矩阵并推导出接触等因素刚度子矩阵和荷载子向量的具体表达式。该方法建模更加方便合理,计算精度、效率介于线性模式的传统DDA法和非线性位移模式的耦合法之间。通过基本算例验证了混合法的有效性,并给出了节理围岩-隧道衬砌整体分析模型的计算结果,体现了新方法的优越性。 相似文献
13.
We have studied the plastic deformation of Mg2SiO4 wadsleyite polycrystals. Wadsleyite was synthesized from a forsterite powder in a multianvil apparatus. It was then recovered
and placed in a second multianvil assembly designed to induce plastic deformation by compression between two hard alumina
pistons. After the deformation experiment, the microstructures are characterized by transmission electron microscopy (TEM)
and large-angle convergent beam electron diffraction (LACBED). Deformation experiments have been carried out at 15–19 GPa
and at temperatures ranging from room temperature to 1800–2000 °C. Five different dislocation types have been identified by
LACBED: [100], 1/2〈111〉, [010], 〈101〉 and [001]. The [001] dislocations result from dislocation reactions and not from activation
of a slip system. The [010] dislocations are activated under high stresses at the beginning of the experiments and further
relax by decomposition into 1/2〈111〉 dislocations or by dissociation into four 1/4[010] partial dislocations. The following
slip systems have been identified: 1/2〈111〉{101}, [100](010), [100](001), [100]{011}, [100]{021}, [010](001), [010]{101} and
〈101〉(010).
Received: 15 July 2002 / Accepted: 14 February 2003
Acknowledgements High-pressure experiments were performed at the Bayerisches Geoinstitut under the EU IHP – Access to Research Infrastructures
Programme (Contract no. HPRI-1999-CT-00004 to D.C. Rubie). P.C. has benefited from a Congé thématique pour recherche from
the University of Lille, and would like to thank warmly all the people in Bayreuth who contributed to this work by daily assistance
and discussions: Nathalie Bolfan-Casanova, Daniel Frost, Jed L. Mosenfelder and Brent Poe. The quality of the preparation
of the TEM specimens by H. Schultze is greatly appreciated. 相似文献
14.
We have studied the dislocation microstructures that develop in (Mg0.9Fe0.1)2SiO4 wadsleyite deformed by simple shear at high pressure. The experiments were performed in a multianvil apparatus with the shear
assembly designed by Karato and Rubie (1997). The samples were synthesized in a separate experiment from high-purity oxides.
The deformation experiments were carried out at 14 GPa and 1300 °C with time durations ranging from 1 to 8 h leading to plastic
shear strains of 60 and 73%, respectively. The microstructures investigated by transmission electron microscopy (TEM) show
that dislocation glide is activated under these conditions over the whole experimental time. The easy slip systems at 1300
°C involve 1/2<111> dislocations gliding in {101} as well as [100] dislocations gliding in (010) and {011}.
Received: 15 July 2002 / Accepted: 14 February 2003
Acknowledgements High-pressure experiments were performed at the Bayerisches Geoinstitut under the EU IHP — Access to Research Infrastructures
Programme (Contract no. HPRI-1999-CT-00004 to D.C. Rubie). The quality of the preparation of the TEM specimens by H. Schultze
is greatly appreciated. 相似文献
15.
Migration of crustal deformation 总被引：2，自引：0，他引：2
Keichi Kasahara 《Tectonophysics》1979,52(1-4)
Observations on the migration rates of crustal deformation, as recently discovered in several tectonic areas, such as the south Kanto and central Tohoku districts, Japan and the West Cordillera Mts., Peru, has opened up a new opportunity for the study of crustal dynamics. Briefly, these examples from coastal areas are characterized by migration landwards with a velocity of about 10–100 km/yr. This agrees well with the velocity of mIgration of seismicity as previously known. Dispersion and dissipation of the deformation waveform are also noted as characteristics.Simple extrapolation of the migration path back toward the ocean may locate a possible origin of the event. In the case of the south Kanto district, for example, the deformation front seems to have originated in the early 1950s from the vicinity of the junction of the Japan and Izu—Mariana trenches. The deformation front in the central Tohoku district, on the other hand, is thought to have originated in the northern part of the Japan Trench in the late 1960s. One may suppose that either a repeated irregular aseismic plate motion generates the deformation events, or that it results from a periodic seismic slip at a plate boundary. In the latter case, the 1953 Boso-oki and the 1968 Tokachi-oki earthquakes might be suspected of generating the deformation fronts in the south Kanto and central Tohoku districts respectively.As Scholz speculated, the migration of a deformation front might trigger earthquakes, if it hits areas of high seismic potential. Studies of migration events can contribute significantly to earthquake prediction studies. 相似文献
16.
The role of internal deformation in resetting argon ages of micas has been investigated by measuring 40Ar/39Ar ratios of biotite and muscovite, before and after experimentally deforming them. Neither mica crushed cataclastically at room temperature on-line with a mass spectrometer showed any measurable change in 40Ar/39Ar age. Muscovite crystals either sheared along the K-interlayer and/or kinked at 400 °C and 100–200 MPa confining pressure, exhibit small (0.7–1.0%) reductions in age and marked increases in bulk diffusion coefficients, as determined from argon release during the initial stages of step-heating between 550 and 810 °C. We conclude that the relatively young ages of fine-grained mica populations in naturally deformed mylonites result primarily from grain size refinement and reductions in length scale for volume diffusion and/or by syntectonic neocrystallization. Internal deformation involving dislocation slip and kinking may contribute to some argon loss by pipe diffusion, but reductions in closure temperature associated with multipath diffusion are small. 相似文献
17.
We report for the first time the occurrence of polygonal faults in sandstone, which is compelling given that layer-bound polygonal fault systems have been observed so far only in fine-grained sediments such as clay and chalk. The polygonal faults are shear deformation bands that developed under shallow burial conditions via strain hardening in dm-wide zones. The edges of the polygons are 1–5 m long. The shear deformation bands are organized as conjugate faults along each edge of the polygon and form characteristic horst-like structures. The individual deformation bands have slip magnitudes ranging from a few mm to 1.5 cm; the cumulative average slip magnitude in a zone is up to 10 cm. The deformation bands heaves, in aggregate form, accommodate a small isotropic horizontal extension (strain <0.005). The individual shear deformation bands show abutting T-junctions, veering, curving, and merging where they mechanically interact. Crosscutting relationships are rare. The interactions of the deformation bands are similar to those of mode I opening fractures. The documented fault networks have important implications for evaluating the geometry of km-scale polygonal fault systems in the subsurface, top seal integrity, as well as constraining paleo-tectonic stress regimes. 相似文献
18.
19.
V. I. Solomatin 《Doklady Earth Sciences》2017,477(2):1426-1429
New results of experimental studies into ice deformation and structural changes are presented. A sequence of structural mechanisms of deformation from polygonization to formation of cracks, cavities and shattering of crystals that replace each other primarily relatively to the load value and the deformation rate is developed. The principal mechanism of creep deformation is crack formation and crystal shattering. A brittleness index for ice deformation is proposed. It is shown that the vesicular texture of ice can be the result of the regeneration of open cracks during deformation. 相似文献
20.
Experimental deformation of partially-melted granite 总被引：18，自引：0，他引：18
An account is given of the experimental deformation of partially-melted granite with melt fractions up to 25% at 800 °C and 300 MPa confining pressure in constant strainrate tests between 10–3 and 10–6 S–1, creep tests and cycling tests. Microscopic study reveals that under these conditions most of the uniform deformation prior to macroscopic shear failure is accomplished by melt redistribution into films perpendicular to the least compressive stress, and by axial fracturing of grains, the latter occurring even at low macroscopic differential stress. The strenght of the partially-melted rock at 10–5 S–1 is found to decrease gradually from about 250 MPa at 5 vol.% melt to about 60 MPa at 15 % melt, and then to drop rapidly to less than 1 MPa at 24% melt. The critical melt fraction separating granular-framework-controlled flow behaviour from suspension-like behaviour is deduced to be approximately 30 to 35 vol.%. At low melt fractions the deforming rock tends to take up externally available melt by a mechanism of dilatancy pumping. The relevance of these results to natural conditions involving partially-melted rocks is discussed. 相似文献