Roof collapse mechanism of weak surrounding rock for deep-buried tunnels under high geostress conditions

High geostress,a typical attribute of tunnels located at significant depths,is crucial in causing stress-induced failure and influencing the stability of the tunnel crown.This study developed an analytical method for the failure mechanism that occurs in deep-buried tunnel roofs,taking into account the influence of geostress.The limit analysis theory was utilized for deriving analytical solutions about the geometry of the collapsing surface and the limit supporting pressure.The collapsing surface obtained by the analytical solution was validated by the findings of the physical model test,which shows a high level of agreement with the actual one.An extensive investigation was done to explore the effects of the lateral pressure coefficients,the tunnel buried depth,the geological conditions of the surrounding rock,the long-short axis ratio,and the size of the tunnel profile.The findings indicate that an increase in the lateral pressure coefficient from 0.5 to 1.5 results in a reduction in the height of the collapsing zone by 2.08 m and the width of the collapsing zone by 1.15 m,while simultaneously increases the limit supporting pressure by 18.9%.The proposed upper bound method accurately determines the limit supporting pressure and the geometry of the collapsing surface,which aligns well with the results acquired through numerical modelling and on-site monitoring in actual engineering applications.The proposed analytical method can serve as a reference for similar crown failure issues of deep-buried tunnels.

Dissolution mechanism of a deep-buried sandstone reservoir in a deep water area:A case study from Baiyun Sag,Zhujiang River(Pearl River)Mouth Basin

Dissolution mechanism and favorable reservoir distribution prediction are the key problems restricting oil and gas exploration in deep-buried layers.In this paper,the Enping Formation and Zhuhai Formation in Baiyun Sag of South China Sea was taken as a target.Based on the thin section,scanning electron microscopy,X-ray diffraction,porosity/permeability measurement,and mercury injection,influencing factors of dissolution were examined,and a dissolution model was established.Further,high-quality reservoirs were predicted temporally and spatially.The results show that dissolved pores constituted the main space of the Paleogene sandstone reservoir.Dissolution primarily occurred in the coarse-and medium-grained sandstones in the subaerial and subaqueous distributary channels,while dissolution was limited in fine-grained sandstones and inequigranular sandstones.The main dissolved minerals were feldspar,tuffaceous matrix,and diagenetic cement.Kaolinization of feldspar and illitization of kaolinite are the main dissolution pathways,but they occur at various depths and temperatures with different geothermal gradients.Dissolution is controlled by four factors,in terms of depositional facies,source rock evolution,overpressure,and fault activities,which co-acted at the period of 23.8–13.8 Ma,and resulted into strong dissolution.Additionally,based on these factors,high-quality reservoirs of the Enping and Zhuhai formations are predicted in the northern slope,southwestern step zone,and Liuhua uplift in the Baiyun Sag.

Mechanical Properties of Deep-buried Marble Material Under Loading and Unloading Tests

The mechanical properties are essentially different when rock material is subjected to loading or unloading conditions. In this study, loading and unloading tests with various confining pressures are conducted to investigate the mechanical properties of marble material samples taken from the deep diversion tunnels of Jinping II Hydropower Station. The stress-strain relationship, failure characteristics and strength criterion are compared and analyzed based on the experiment results. The results show： in the loading and unloading test, peak strength, lateral strain, axial strain and plastic deformation increase significantly as the confining pressure increases. Lateral strain increased significantly and obvious lateral dilatancy can be observed to the change of confining pressure; The fracture mode is mainly the single shear fracture for the triaxial compression test and post-peak test, angle between the failure surface and the ends of the rock material becomes smaller as the confining pressure increases. Hock-Brown strength criterion reflects the strength characteristics of marble material under two different unloading conditions, and has some supplementary effects to the rock material of mechanical field.

Comparison of vibrations induced by excavation of deep-buried cavern and open pit with method of bench blasting

The measured data of vibrations induced by excavation of deep-buried cavern and open pit with method of bench blasting were analyzed by Fourier Transform and Wavelet Transform,and the characteristics of vibrations induced under these two circumstances were studied.It is concluded that with the similar rock condition and drilling-blasting parameters,vibration induced by bench blasting in deep-buried cavern has a higher main frequency and more scattered energy distribution than that in open pit.The vibration induced by bench blasting in open pit is mainly originated from the blast load,while the vibration induced by bench blasting in deep-buried cavern is the superposition of vibrations induced by blast load and transient release of in-situ stress.The vibration induced by transient release of in-situ stress increases with the stress level.

Analytical solution for steady seepage into a circular deep-buried mountain tunnel with grouted zone in anisotropic strata

Due to the existence of a large number of discontinuous fractures and interfaces in tunnel surrounding rocks,the groundwater inflow into tunnel generally presents significant anisotropy.Therefore,it is of great significance to consider the anisotropic permeability when dealing with water gushing-induced engineering accidents in water-rich mountain tunnels with large burial depth.In this study,based on the complex variable method and the seepage flow theory,a theoretical model of water inflow into a deep-buried circular tunnel in a fully saturated,anisotropic and semi-infinite aquifer is developed.The influence of grouted zone,initial support and secondary lining is fully considered.By comparison to the existing analytical methods and numerical results,the reliability of this proposed analytical solution is well validated.It is indicated from the parametric study that the groundwater inflow into tunnel presents an upward trend with an increasing value of the strata permeability in the vertical direction.Moreover,the water inflow rate and the total water head decrease with the growth of the thickness of grouting circle.It is suggested that reasonable grouting thickness and permeability should be controlled to enhance the grouting effect.This study provides a practical method for estimating the water inflow into a deep-buried,grouted and lined mountain tunnel considering the anisotropic strata permeability.

Forecasting of water yield of deep-buried iron mine in Yanzhou, Shandong

This paper compares analytical and numerical methods by taking the forecasting of water yield of deep-buried iron mine in Yanzhou, Shandong as an example. Regarding the analytical method, the equation of infinite and bilateral water inflow boundary is used to forecast the water yield, and in the case of numerical simulation, we employed the GMS software to establish a model and further to forecast the water yield. On the one hand, through applying the analytical method, the maximum water yield of mine 1 500 m deep below the surface was calculated to be 13 645.17 m3/d; on the other hand, through adopting the numerical method, we obtained the predicted result of 3 816.16 m3/d. Meanwhile, by using the boundary generalization in the above-mentioned two methods, and through a comparative analysis of the actual hydro-geological conditions in this deep-buried mine, which also concerns the advantages and disadvantages of the two methods respectively, this paper draws the conclusion that the analytical method is only applicable in ideal conditions, but numerical method is eligible to be used in complex hydro-geological conditions. Therefore, it is more applicable to employ the numerical method to forecast water yield of deep-buried iron mine in Yanzhou, Shandong.

Numerical simulation of zonal disintegration of surrounding rock in the deep-buried chamber

Zonal disintegration is the phenomenon of cyclical rupture zone and nonrupture zone in the surrounding rock of a deep-buried chamber,which is different from that of a shallow chamber.Based on the finite difference software FLAC3D,the numerical simulation of surrounding rock with different mechanical parameters was conducted by using the SU model(Bilinear Strain-Softening Ubiquitous-Joint).The influences of buried depth,cohesion,and internal friction angle of surrounding rock on zonal disintegration were analyzed to reveal the influence law.The results show that:(1)after the chamber excavation,multiple rupture zones gradually extend from the chamber surface or adjacent periphery to the deep surrounding rock.In the extension process,a single rupture zone may be forked into two or even multiple rupture zones,which cross each other and form the zonal disintegration zone.(2)Zonal disintegration is affected by bothσ(in situ stress)and U_(cs)(uniaxial compression strength).Smaller U_(cs)and largerσwill lead to zonal disintegration.(3)The zoning fracture is not obvious in the case ofσ≤U_(cs).In the reverse case,zoning fracture appears remarkably in the surrounding rock around the chamber.These results reveal the influence law of zonal disintegration and provide theoretical support for the design of deep-buried chambers.

Stress wave propagation and incompatible deformation mechanisms in rock discontinuity interfaces in deep-buried tunnels

Complex weak structural planes and fault zones induce significant heterogeneity,discontinuity,and nonlinear characteristics of a rock mass.When an earthquake occurs,these characteristics lead to extremely complex seismic wave propagation and vibrational behaviors and thus pose a huge threat to the safety and stability of deep buried tunnels.To investigate the wave propagation in a rock mass with different structural planes and fault zones,this study first introduced the theory of elastic wave propagation and elastodynamic principles and used the Zoeppritz equation to describe wave field decomposition and develop a seismic wave response model accordingly.Then,a physical wave propagation model was constructed to investigate seismic waves passing through a fault,and dynamic damage was analyzed by using shaking table tests.Finally,stress wave attenuation and dynamic incompatible deformation mechanisms in a rock mass with fault zones were explored.The results indicate that under the action of weak structural planes,stress waves appear as a complex wave field decomposition phenomenon.When a stress wave spreads to a weak structural plane,its scattering may transform into a tensile wave,generating tensile stress and destabilizing the rock mass;wave dynamic energy is absorbed by a low-strength rock through wave scattering,which significantly weakens the seismic load.Wave propagation accelerates the initiation and expansion of internal defects in the rock mass and leads to a dynamic incompatible deformation.This is one of the main causes for large deformation and even instability within rock masses.These findings provide an important reference and guide with respect to stability analysis of rock mass with weak structural planes and fault zones.

The determination of sedimentary environment and associated energy in deep-buried marine carbonates:insights from natural gamma ray spectrometry log

It has always been challenging to determine the ancient sedimentary environment and associated energy in deep-buried marine carbonates.The energy represents the hydrodynamic conditions that existed when the carbonates were deposited.The energy includes light and chemical energies in compounds and kinetic energy in currents and mass flow.Deep-buried marine carbonates deposited during the Ordovician depositional period in the eastern Tarim Basin result from a complex interplay of tectonics,sedimentation,and diagenesis.As a result,determining the ancient sedimentary environment and associated energy is complex.The natural gamma-ray spectrometry(GRS)log(from 12 wells)is used in this paper to conduct studies on the sedimentary environment and associated energy in deep-buried marine carbonates.The findings show that the values of thorium(Th),uranium(U),potassium(K),and gamma-ray without uranium(KTh)in a natural GRS log can reveal lithological associations,mineral composition,diagenetic environment,stratigraphic water activity,and ancient climatic change.During the Ordovician,quantitative analysis and determination of sedimentary environment energy are carried out using a comprehensive calculation of natural GRS log parameters in typical wells(penetrating through the Ordovician with cores and thin sections)of well GC4,well GC6,well GC7,and well GC8.The results show that GRS log can determine different lithology associations in typical wells than a sieve residue log.Furthermore,cores and thin sections can be used to validate the determination of lithology associations.Based on the determination of lithology associations,the lithology associations that reflect the sedimentary environment and associated energy can be analyzed in a new approach.Furthermore,the sedimentary environment energy curve derived from a natural GRS log can reveal hydrodynamic fluctuations during depositional periods,which will aid in the discovery of carbonate reservoirs,establishing sequence stratigraphic frameworks,and the reconstruction of sea-level changes in the future.

盐穴储气库运行压力对腔体稳定性的影响

为考察盐穴储气库长期运行的稳定性，对3种不同形态的盐穴储气库模型在变化的运行压力下从腔壁应力分布及溶腔体积变化两方面进行分析。研究表明：盐穴腔体投入运行的初期是腔壁应力水平最高的时期，应力集中主要出现在腔壁曲率较大的部分；在变化的内压之下，应力松弛现象同样明显，腔壁应力在逐渐降低的同时，各部位的应力水平趋于均匀；在4～14．5MPa的运行压力下，溶腔应力变化及体积变化未随运行压力变化出现明显波动；模拟10年的运行之后，梨形、近似球形和圆锥形储气库的体积将分别缩小27％、22％和37％，体积缩减速度在不断趋于平缓。

多技术辅助神经内镜下侵袭海绵窦的垂体腺瘤的治疗

目的探讨多技术辅助神经内镜下侵袭海绵窦的巨大垂体腺瘤的手术疗效。方法对比分析同期72例神经内镜下和55例显微镜下侵袭海绵窦的巨大垂体腺瘤的手术疗效,两组均采用扩大经蝶入路,术中应用神经导航和多普勒,并对两组临床资料进行统计学分析。结果神经内镜组与显微镜组在肿瘤全切率、手术时间、术后鼻腔通畅率和术后复发率方面差异具有统计学意义(P=0.004,P=0.0003,P=0.000,P=0.002);在脑脊液漏、术后尿崩、颅神经损伤等方面差异无统计学意义(P>0.05)。结论多技术辅助神经内镜下扩大经蝶入路是治疗侵袭海绵窦的巨大垂体腺瘤的首选手术方法,外侧海绵窦入路和分子生物学研究为侵袭性垂体腺瘤的治疗提供了更为广阔的前景。

14例梭形细胞血管内皮瘤的临床病理分析

目的观察梭形细胞血管内皮瘤的临床病理特征和生物学行为，探索这一。近年来提出的肿瘤是否为一独立类型及其预后。方法运用组织病理学、免疫组织化学和随访观察资料，研究本瘤的诊断标准、鉴别诊断要点和良恶性。结果本瘤见于各种年龄组，男女性别无显著差异。病变位于真皮和皮下。组织学上由梭形细胞区和海绵状血管区组成。梭形细胞区主要成分为梭形细胞，也可见一些上皮样细胞。5例病人做了第八因子相关抗原和荆豆素的免疫组织化学。两者均在海绵状血管的内皮细胞呈阳性结果。而在校形细胞区，两者各有4例呈微弱阳性，各有1例明显阳性。8例病人获随访结果，其中5例在原部位有l－3次复发，但无1例转移。结论我们认为梭形细胞血管内皮瘤是一新的独立类型的血管肿瘤，可能是良性的。其“高复发率”可能与肿瘤多灶性和浸润性生长而难以切除干净有关。

颈内动脉海绵窦段分支及分布的显微解剖

目的 :为海绵窦的直接手术提供显微解剖学基础。方法 :采用 48侧成人新鲜海绵窦标本 ,颈内动脉灌注苯乙烯 (ABS) ,然后在手术显微镜下解剖观察。结果 :脑膜垂体干出现率为 10 0 % ,脑膜垂体干可分为两型 ,典型的脑膜垂体干出现率为 5 8.3 % ,非典型的脑膜垂体干又分为单干型和非单干型 ,前者出现率为 3 1.3 % ,后者为 10 .4%。海绵窦下动脉出现率为 95 .8% ,垂体被囊动脉为 3 1.3 %。另外眼动脉的出现率为 10 .4%。两侧颈内动脉海绵窦段分支之间的吻合 ,提供了重要的侧支循环血液供应。结论 :本文对颈内动脉海绵窦段分支的显微解剖结果 ,对临床显微外科、血管介入、影像学有指导意义。

深部地下洞室施工期围岩大变形机制分析

大岗山水电站引水发电系统地下洞室埋深大,花岗岩因风化卸荷强烈,岩脉破碎带发育,应力较高。在施工过程中,岩脉、断层穿越的主变室部位出现较大的变形,严重影响施工安全与进度。采用地质调查和现场监测的方法,结合现场施工情况分析主变室围岩大变形特征和机制,提出2种可能的大变形破坏模式,分析影响围岩大变形的因素,并评价主变室的稳定性。研究结果表明:主变室围岩大变形主要受辉绿岩脉8 1和断层f59,f60控制,同时,地应力高、施工强度大、支护进度滞后加剧围岩的大变形。深部地下洞室施工期的地质调查及现场监测可以及时预测高应力区卸荷围岩的大变形,以确保洞室施工期的稳定安全。研究成果对类似工程具有重要的参考价值。

复方平阳霉素局部注射治疗大面积海绵状血管瘤

目的探讨大面积海绵状血管瘤的治疗方法。方法回顾性分析5年来收治的病变直径超过15 cm的55例大面积海绵状血管瘤,采用复方平阳霉素液局部注射(其中4例结合手术)治疗的特点和方法。结果第一疗程20例治愈,治愈率36.36%;第二个疗程31例治愈,治愈率56.36%。另4例结合手术治疗均治愈。结论复方平阳霉素液局部注射治疗大面积海绵状血管瘤安全有效,可在临床使用。

显微手术治疗小脑海绵状血管瘤

目的总结小脑海绵状血管瘤的临床表现及手术治疗效果。方法对12例均经手术切除和病理证实的小脑海绵状血管瘤进行回顾性分析。结果 11例急性起病,表现为小脑自发性出血。慢性起病1例,表现为渐进性共济失调、行走不稳。头颅MRI平扫与增强多表现为T1高信号,T2高或混杂信号,病灶周围有环形低信号带。磁敏感加权成像序列(SWI)更有助于诊断。12例均采用显微手术治疗,所有病灶均完整切除,疗效满意。结论自发性出血是本病的主要症状,多有共济失调等小脑受损体征。MRI具有较高的诊断特异性,手术是处理小脑海绵状血管瘤安全和有效的首选方法。

含高盐份泥岩夹层的盐岩蠕变特性研究

含高盐份泥岩夹层的盐岩蠕变特性是油气储库稳定性的关键问题所在。通过对湖北应城含高盐份泥岩夹层的盐岩160天的单轴压缩蠕变实验研究,可知湖北应城含高盐份泥岩夹层的盐岩具有良好的蠕变特性,且纯盐岩蠕变应变高于泥岩夹层,横向应变大于泥岩夹层。根据试验结果,分析了含高盐份泥岩夹层的盐岩的蠕变曲线特征,建立了含高盐份泥岩夹层的盐岩的蠕变理论模型,获得了含高盐份泥岩夹层的盐岩的粘弹塑性本构方程,并拟合了参数,为我国含高盐份泥岩夹层的盐岩矿床油气储库的稳定性分析提供了依据。

颈内动脉海绵窦段动脉瘤10例临床诊治体会

目的：探讨颈内动脉海绵窦段动脉瘤的诊治方法。方法：对8例颈内动脉海绵窦段动脉瘤采用血管内治疗，2例内科保守治疗随访，分析其治疗效果。结果：术后血管造影8例患者中的10个动脉瘤显示：6个动脉瘤不显影，4个绝大部分不显影；2例患者中的2个动脉瘤无变化。随访1～22个月，8例临床症状较前明显好转，2例内科保守（未介入治疗者）无明显变化。结论：对于有症状的颈内动脉海绵窦段动脉瘤，通过完善的术前评估，采取个性化血管内治疗可以减轻、甚至解除患者的临床症状，达到治愈的疗效，是综合治疗海绵窦段动脉瘤的安全、有效及并发症少的重要方法之一。而对无症状或者轻微症状的小动脉瘤定期随访观察是安全的。

夹层对岩盐储气库水溶建腔的影响分析

为了研究夹层对岩盐储气库水溶建腔的影响,根据小挠度的薄板弯曲模型,建立岩盐地层中夹层的数学模型,通过对岩盐储气库水溶建腔进行动态模拟数值计算,分析夹层对岩盐储气库水溶建腔形态和建腔周期的影响规律,同时给出了夹层的强度较核和断裂极限长度的求解方法。研究结果表明,岩盐储气库应选择在夹层数量尽量少而薄的地层条件下建设,有利于腔体形态的控制,同时能够有效降低溶腔周期。

大型地下洞室群地震模拟振动台试验研究(Ⅱ):试验方案设计

为了解大型地下洞室群在地震过程中的动态响应特征,以大渡河流域的大岗山水电站大型地下洞室群为原型,开展地震模拟振动台物理模型试验研究。作为国内外首次进行此类振动台试验研究,系统介绍整个试验的方案设计。首先,根据本次试验的目的和特性,给出试验基本简化原则,并对模型体系进行相似设计,按照完全相似模型推导出各物理量的动力相似常数、确定模拟范围、模型尺寸和相似材料配比。然后,对试验边界条件进行设计,确定了作为柔性边界的聚苯乙烯泡沫板的材料和几何参数,制作了用于测量围岩内部应力的应变砖传感器,并介绍模型制作、洞室成型与开挖等工艺步骤;最后,确定试验输入波形,并按相似理论要求进行调整,给出模型试验的加载工况。经后期试验数据的分析,证明试验条件简化合理,模型设计与制作成功。一整套模型设计方法与制作工艺,可供今后类似试验作为参考。