Three-dimensional pseudo-dynamic reliability analysis of seismic shield tunnel faces combined with sparse polynomial chaos expansion

To address the seismic face stability challenges encountered in urban and subsea tunnel construction,an efficient probabilistic analysis framework for shield tunnel faces under seismic conditions is proposed.Based on the upper-bound theory of limit analysis,an improved three-dimensional discrete deterministic mechanism,accounting for the heterogeneous nature of soil media,is formulated to evaluate seismic face stability.The metamodel of failure probabilistic assessments for seismic tunnel faces is constructed by integrating the sparse polynomial chaos expansion method(SPCE)with the modified pseudo-dynamic approach(MPD).The improved deterministic model is validated by comparing with published literature and numerical simulations results,and the SPCE-MPD metamodel is examined with the traditional MCS method.Based on the SPCE-MPD metamodels,the seismic effects on face failure probability and reliability index are presented and the global sensitivity analysis(GSA)is involved to reflect the influence order of seismic action parameters.Finally,the proposed approach is tested to be effective by a engineering case of the Chengdu outer ring tunnel.The results show that higher uncertainty of seismic response on face stability should be noticed in areas with intense earthquakes and variation of seismic wave velocity has the most profound influence on tunnel face stability.

Discussion on Construction Technology of Subway Tunnel Expansion under Bridge Foundation

As the urban populations grow,the number and size of subway construction projects are increasing while also meeting higher construction standards.So,subway construction projects must have a better understanding of construction technology.This article focuses on the construction technology of the subway tunnel expansion under the bridge foundation.By analyzing the engineering characteristics of the bridge foundation and using a project as an example,this article provides a detailed discussion of the construction process of tunnel expansion under a bridge foundation.This article aims to serve as a reference for subway tunnel construction in China to ensure the key points of construction technology are understood,thus improving construction quality and laying a solid technical foundation for the sustainable development of urban rail engineering.

Spectral measurements of hypervelocity flow in an expansion tunnel

Atmospheric reentry vehicles and planetary probes fly through the atmosphere at hypervelocity speed. At such speed, there is a significant proportion of heat load to the vehicle surface due to radiative heating. Accurate prediction needs a good knowledge of the radiation spectrum properties. In this paper, a high-speed camera and spectrograph coupled to an intensified charge-coupled device have bee n impleme nted to inv estigate the rad i at io n flow over a semi-cylinder model. The experiments were carried out in the JF16 expansi on timnel with secondary shock velocity of 7.9 km·s^-1. Results show that the emissio n spectrum comprises several atomic lines and molecular band systems. We give detailed data of the radiation spectrum, shock shape, shock detached distance and radiation intensity varying with space and wavelength. This valuable experimental dataset will be helpful to validate computational fluid dynamics codes and radiation models, which equates to increased prediction accuracy of radiation heating. Also, some suggestions for spectral measurement in hypervelocity flow field were list in the end.

Support design method for deep soft-rock tunnels in non-hydrostatic high in-situ stress field

Due to the long-term plate tectonic movements in southwestern China,the in-situ stress field in deep formations is complex.When passing through deep soft-rock mass under non-hydrostatic high in-situ stress field,tunnels will suffer serious asymmetric deformation.There is no available support design method for tunnels under such a situation in existing studies to clarify the support time and support stiffness.This study first analyzed the mechanical behavior of tunnels in non-hydrostatic in-situ stress field and derived the theoretical equations of the ground squeezing curve(GSC)and ground loosening curve(GLC).Then,based on the convergence confinement theory,the support design method of deep soft-rock tunnels under non-hydrostatic high in-situ stress field was established considering both squeezing and loosening pressures.In addition,this method can provide the clear support time and support stiffness of the second layer of initial support.The proposed design method was applied to the Wanhe tunnel of the China-Laos railway in China.Monitoring data indicated that the optimal support scheme had a good effect on controlling the tunnel deformation in non-hydrostatic high in-situ stress field.Field applications showed that the secondary lining could be constructed properly.

In-situ observations of damage-fracture evolution in surrounding rock upon unloading in 2400-m-deep tunnels

The damage-fracture evolution of deep rock mass has obvious particularity,which is revealed in 2400-mdeep tunnels by field tests.The evolution of the excavation damaged zone depth is consistent with that of the fractured zone depth.The ratio of the excavation damaged zone depth to the excavation fractured zone depth is greater than 2.0 in a rock mass with both high strength and good integrity,but less than1.5 in a rock mass with lower strength or poor integrity.Zonal disintegration in a rock mass with high strength and fair integrity is more likely to occur when it contains more than two groups of primary fractures in damaged zones.Fractures develop outward in zonal disintegration but are totally different from the single-zone fracture,in which the fractures develop inward,and it is the starting position of the fractured zone when the excavation surface of the middle pilot is 7–9 m close to the pre-set borehole and it stops after the excavation surface of the baseplate is 11–14 m away.The most intense evolution occurs around 2–4 m from the pre-set borehole in the sidewall expansion stage.The research results provide a reference for the monitoring scheme and support design of CJPL-Ⅲin its future construction.

Graphene/Rh(111) Structure Studied Using In-Situ Scanning Tunneling Microscopy

Scanning tunnel microscopy （STM） is performed to verify if an Rh ＇nails＇ structure is formed accompanying the graphene growing during chemical vapor deposition. A structure of a graphene island in an Rh vacancy island is used as the start. While the graphene island is removed by oxygenation, the variations of the Rh vacancy island are imaged with an in-situ high-temperature STM. By fitting with our model and calculations, we conclude that the best fit is obtained for 0% Rh, i.e., for the complete absence of nails below graphene on Rh（111）. That is, when graphene is formed on Rh（111）, the substrate remains fiat and does not develop a SUPPorting nail structure.

Impact of surface-reflected seismic waves on the seismic isolation performance of circular tunnel isolation layers

Seismic isolation is an effective strategy to mitigate the risk of seismic damage in tunnels.However,the impact of surface-reflected seismic waves on the effectiveness of tunnel isolation layers remains under explored.In this study,we employ the wave function expansion method to provide analytical solutions for the dynamic responses of linings in an elastic half-space and an infinite elastic space.By comparing the results of the two models,we investigate the seismic isolation effect of tunnel isolation layers induced by reflected seismic waves.Our findings reveal significant differences in the dynamic responses of the lining in the elastic half-space and the infinitely elastic space.Specifically,the dynamic stress concentration factor(DSCF)of the lining in the elastic half-space exhibits periodic fluctuations,influenced by the incident wave frequency and tunnel depth,while the DSCF in the infinitely elastic space remain stable.Overall,the seismic isolation application of the tunnel isolation layer is found to be less affected by surface-reflected seismic waves.Our results provide valuable insights for the design and assessment of the seismic isolation effect of tunnel isolation layers.

Assessing the range of blasting-induced cracks in the surrounding rock of deeply buried tunnels based on the unified strength theory

Blasting-induced cracks in the rock surrounding deeply buried tunnels can result in water gushing and rock mass collapse,posing significant safety risks.However,previous theoretical studies on the range of blasting-induced cracks often ignore the impact of the in-situ stress,especially that of the intermediate principal stress.The particle displacement−crack radius relationship was established in this paper by utilizing the blasthole cavity expansion equation,and theoretical analytical formulas of the stress−displacement relationship and the crack radius were derived with unified strength theory to accurately assess the range of cracks in deep surrounding rock under a blasting load.Parameter analysis showed that the crushing zone size was positively correlated with in-situ stress,intermediate principal stress,and detonation pressure,whereas negatively correlated with Poisson ratio and decoupling coefficient.The dilatancy angle-crushing zone size relationship exhibited nonmonotonic behavior.The relationships in the crushing zone and the fracture zone exhibited opposite trends under the influence of only in-situ stress or intermediate principal stress.As the in-situ stress increased from 0 to 70 MPa,the rate of change in the crack range and the attenuation rate of the peak vibration velocity gradually slowed.

公路隧道改扩建方案比选及施工工法数值模拟

为了分析公路隧道改扩建方案的可行性以及公路隧道不同改扩建施工工法时围岩扰动后的力学特性,以济南绕城高速港沟立交至殷家林枢纽段改扩建工程某公路隧道为研究对象,比选3种公路隧道改扩建方案;建立三维数值模型,对比最佳方案不同施工工法时的围岩力学特性;利用有限差分软件FLAC 3D内置的FISH语言对围岩塑性区体积求和计算,探讨左线公路隧道改扩建过程对右线公路隧道的影响。结果表明:综合考虑改扩建施工难度、运营安全性、后期提速、管养难度、工程造价等因素,确定公路隧道改扩建为双八车道隧道为公路隧道改扩建最佳方案;围岩位移随着公路隧道开挖深度的增加而增大,并且在开挖断面处增大最快;围岩的压应力集中区为公路隧道的拱脚处,而拱顶和拱底压应力较小并向拉应力转变;围岩塑性区破坏方式以剪切破坏为主,可及时施作支护结构控制围岩变形;综合考虑公路隧道改扩建施工的可行性、安全性和经济性,确定中隔壁法为公路隧道改扩建最优施工工法。

邻近既有建筑浅埋隧道扩挖施工方案比选

依托采用中洞法扩建的某隧道工程,建立数值模型对中洞先行与双侧导坑先行两种方案的施工过程开展模拟分析,研究目标断面在不同施工工序下拱顶沉降、水平收敛以及中洞收敛随施工步的变化。结果表明:中洞先行方案早于双侧导坑先行方案形成闭合拱结构,整体承载能力较强,施工过程中拱顶沉降较小;双侧导坑方案的水平收敛及中洞收敛均优于中洞先行方案,但施工过程中存在明显偏压现象。若扩建后隧道主要承受竖向荷载时,建议采用中洞先行施工方案;若竖向荷载较小,水平应力较大时,建议采用双侧导坑先行方案。

Experimental and numerical investigation into the non-explosive excavation of tunnels

The use of explosives is restricted on some important holidays,and the handling of unexploded charge is very dangerous.Therefore,an innovative non-explosive technology called instantaneous expansion(IE)was developed for tunneling.IE,whose components are derived from solid wastes such as coal gangue and straw conduces to realizing the reuse of waste.Moreover,its cost is lower than explosives.Blind guns of IE are easy to treat with water.The IE tunneling method is classified into two categories,i.e.IE with a single fracture(IESF)and IE with multiple fractures(IEMF),which are used to form the tunnel crosssection directionally cross-section and to fragment the rocks inside the cross-section,respectively.In this study,the principle of IE tunneling was elaborated first.Then,tunneling experiments and numerical simulations were performed on IE,conventional blasting(CB)and shaped charge blasting(SCB)in comparison.The experimental and numerical results show that IE achieved the best performance of directional rock breaking and corresponded to the most minor excavation-induced damage zone of the surrounding rock.Besides,the tunnel cross-section created by IE was flat and smooth.Comparing IE with CB and SCB,the over/under-excavation area decreased by 64%and 17%,and the excavation-induced damage zone fell by 26%and 11%,respectively.The range of the loose circle is reduced,which is conducive to improving the long-term stability of the roadway.The research provides a safe and economical tunneling method with excellent application prospects.

Pavement structure and materials design for sea-crossing bridges and tunnel:Case study of the Hong Kong-Zhuhai-Macao Bridge

With the continuous development of bridge and tunnel construction technologies,large-scale sea-crossing bridges and tunnels have gradually become the preferred choice for regional traffic.The construction technology of Hong Kong-Zhuhai-Macao Bridge(HZMB),one of the most representative sea-crossing passageways,is instructive for the construction of other large sea-crossing infrastructures.At present,the pavement design method of sea-crossing passageways lacks pertinence as it still refers to specifications for design of common pavement.Therefore,it is necessary to consider the bridge and tunnel pavement of HZMB as a typical example to analyze key technical problems encountered in its design,construction and operation.Novel solutions for material selection and structural design built upon the analysis of such critical problems should thus follow up.Based on comprehensive literature research,it can be found that environmental variability,tunnel closure,structural differential settlement and expansion deformation are the key technical problems faced by pavement of sea-crossing passageways.In view of the environmental variability,the steel deck-paving material and structure design of GMA-10 t SMA-13 is innovatively proposed.As for the closure of immersed tube tunnel,warm-mix flame retardant asphalt mixture is used to control pavement design through key indexes such as temperature and limit oxygen index.Regarding the deformation of immersed pipe joints,BJ200 asphalt seamless expansion joint material is introduced,which effectively satisfies the multi-directional deformation between pipe joints and ensures the smoothness of the road surface and driving comfort.For segmental joints,double-layer waterproof-coiled material is used to effectively prevent reflective cracks while ensuring the continuity of asphalt concrete pavement.Therefore,this paper provides a panel of ideas and methods for the pavement design of the same type of sea-crossing passageways.

Predictive analysis of stress regime and possible squeezing deformation for super-long water conveyance tunnels in Pakistan

The prediction of the stress field of deep-buried tunnels is a fundamental problem for scientists and engineers. In this study, the authors put forward a systematic solution for this problem. Databases from the World Stress Map and the Crustal Stress of China, and previous research findings can offer prediction of stress orientations in an engineering area. At the same time, the Andersonian theory can be used to analyze the possible stress orientation of a region. With limited in-situ stress measurements, the Hock-Brown Criterion can be used to estimate the strength of rock mass in an area of interest by utilizing the geotechnical investigation data, and the modified Sheorey＇s model can subsequently be employed to predict the areas＇ stress profile, without stress data, by taking the existing in-situ stress measurements as input parameters. In this paper, a case study was used to demonstrate the application of this systematic solution. The planned Kohala hydropower plant is located on the western edge of Qinghai-Tibet Plateau. Three hydro-fracturing stress measurement campaigns indicated that the stress state of the area is SH - Sh 〉 Sv or SH 〉Sv 〉 Sh. The measured orientation of Sn is NEE （N70.3°-89°E）, and the regional orientation of SH from WSM is NE, which implies that the stress orientation of shallow crust may be affected by landforms. The modified Sheorey model was utilized to predict the stress profile along the water sewage tunnel for the plant. Prediction results show that the maximum and minimum horizontal principal stres- ses of the points with the greatest burial depth were up to 56.70 and 40.14 MPa, respectively, and the stresses of areas with a burial depth of greater than 500 m were higher. Based on the predicted stress data, large deformations of the rock mass surrounding water conveyance tunnels were analyzed. Results showed that the large deformations will occur when the burial depth exceeds 300 m. When the burial depth is beyond 800 m, serious squeezing deformations will occur in the surrounding rock masses, thus requiring more attention in the design and construction. Based on the application efficiency in this case study, this prediction method proposed in this paper functions accurately.

高速铁路泥岩隧道仰拱底鼓控制技术研究

研究目的:为分析基底围岩劣化作用下泥岩隧道仰拱底鼓变形的控制效果,运用数值模拟的研究方法,建立高速铁路泥岩隧道有限元模型,考虑隧道开挖条件下模拟基底围岩吸湿膨胀和软化作用,选用底板与锁脚锚杆加固的控制技术,对比分析加固前后隧周围岩的竖向位移、填充层及仰拱的变形特性。研究结论:(1)锚杆加固基底可有效控制隧底围岩隆起,对隧底隆起的控制效果膨胀阶段优于软化阶段;(2)锚杆加固前后仰拱、填充层的底鼓位移曲线均呈“钟形”对称分布;(3)仰拱、填充层中心位置处的底鼓变形最大;(4)本研究结果可为高速铁路泥岩隧道仰拱底鼓病害防治与加固提供参考依据。

关节镜联合肘管扩大成型术治疗肘关节骨性关节炎伴肘管综合征疗效观察

目的探讨关节镜联合肘管扩大成型术治疗肘关节骨性关节炎伴肘管综合征的临床疗效。方法选择2020年9月至2023年8月河北省沧州中西医结合医院骨外科收治的101例肘关节骨性关节炎伴肘管综合征患者为研究对象,按照手术方式不同将患者分为观察组(n=51)和对照组(n=50)。观察组患者采用关节镜联合肘管扩大成型术,对照组患者采用常规肘管扩大成型术。观察并记录2组患者的手术时间、术中出血量、住院时间、并发症发生情况。分别于术前、术后6个月时,采用Mayo肘关节功能评分(MEPS)评估2组患者的肘关节功能,采用日常生活活动能力评定表(ADL)评估2组患者的日常生活能力,采用视觉模拟评分(VAS)评估2组患者的疼痛程度;使用关节量角器测量肘关节旋前度数、旋后度数、屈伸度数,评估2组患者的肘关节活动度;使用Keypoint型肌电图仪检测小指展肌的复合肌肉动作电位(CMAP)、尺神经的神经传导速度(NCV)、运动诱发电位潜伏期(MEPLP),评估2组患者神经恢复情况。结果观察组患者的手术时间、住院时间显著短于对照组,术中出血量、并发症显著少于对照组(P<0.05)。术前,观察组和对照组患者的MEPS、ADL、VAS评分比较差异无统计学意义(P>0.05);术后6个月,观察组患者的MEPS、ADL评分显著高于对照组,VAS评分显著低于对照组(P<0.05)。术前,观察组和对照组患者的旋前度数、旋后度数、屈伸度数比较差异无统计学意义(P>0.05);术后6个月,2组患者的旋前度数、旋后度数、屈伸度数显著高于术前(P<0.05),观察组和对照组患者的旋前度数、旋后度数、屈伸度数比较差异无统计学意义(P>0.05)。术前,观察组和对照组患者的CMAP、NCV、MEPLP比较差异无统计学意义(P>0.05);术后6个月,观察组患者的CMAP、NCV显著高于对照组,MEPLP显著低于对照组(P<0.05)。结论常规肘管扩大成型术、关节镜联合肘关节扩大成型术均可改善肘关节骨性关节炎伴肘管综合征患者的肘关节活动度,但后者损伤更小,恢复更快,在提升肘关节功能及日常生活能力、减轻疼痛程度、调节肌电图检查指标等方面效果更佳,且并发症更少。

稻壳灰替代型微膨胀同步注浆料的制备及性能研究

为解决盾构渣土外运和堆放造成的成本和环境污染问题,并实现固体废弃物资源化再利用的目的,依托郑州地铁十号线某区段盾构工程,利用掘进渣土替代砂、粉煤灰、膨润土,并以稻壳灰(RHA)替代部分水泥制备微膨胀同步注浆料,探究RHA掺量、渣土粒径、水胶比、膨胀剂类型及掺量对同步注浆料工作性能及力学性能的影响。结果表明,RHA对浆料稠度和凝结时间影响较大,RHA掺量越高,浆料稠度越小,凝结时间越短。当RHA掺量为25%(以水泥质量之比计)时,浆料稠度降低27.5%,凝结时间缩短39.9%。随着RHA掺量增大,浆料抗压强度呈先降低后升高趋势。随着渣土粒径增大,浆料稠度和凝结时间减小。生石灰粉和高效静态破碎剂(HSCA)作为膨胀剂会降低浆料的稠度,但可有效增大凝结时间及抗压强度;当HSCA质量分数超过3%时,膨胀效果优于生石灰粉。经试验确定水胶比2.6、RHA掺量25%、采用大粒径渣土以及适当加入膨胀剂,可以使浆料各项指标符合工程要求,为盾构渣土和稻壳灰的再利用提供一种新思路。

南京定淮门长江隧道新增自动灭火系统设计探讨

南京定淮门长江隧道为国内已通车的最长水下双管双层盾构隧道,鉴于定淮门长江隧道内现状无自动灭火系统,从隧道运营安全及防灾救援的角度考虑,拟在隧道内增设自动灭火系统。通过对国内水下隧道自动灭火系统设计的研究现状进行分析后,对隧道新增泡沫/水喷雾系统设计的重难点进行了分析,详细介绍了其针对性的设计解决方案及系统中的重要设备设施,包括:隧道专用泡沫喷头的选型、隧道泡沫/水喷雾系统分区设计、新增消防泵房及消防水池选址、消防管道设置、水力计算、系统控制要求及运行控制系统的设计等,总结了设计中的创新点并进行了展望。

既有隧道不同扩挖宽度下锚杆参数的优化

以黄山洞隧道工程为依托,通过对现场数据的监测和利用有限元分析软件Midas GTS NX进行数值模拟,分析了不同扩挖宽度下隧道拱顶沉降值、周边收敛值和围岩有效应力变化的规律,并改变锚杆的长度和锚杆间距,分析在不同锚杆长度下围岩有效应力、衬砌应力以及锚杆应力的变化规律,确定了不同扩挖宽度下最优的锚杆长度和锚杆间距.研究结果表明:随着扩挖宽度的增加,围岩有效应力由大至小依次为拱脚处压应力、拱腰处压应力、拱顶处压应力和仰拱处拉应力;拱顶处压应力随扩挖宽度的增大而减小,拱腰处压应力随扩挖宽度的增大而增大,但增大趋势不明显;受单侧扩挖方式的影响,扩挖侧的应力大于非扩挖侧;拱脚处受到应力集中的影响,其压应力随着扩挖宽度的增大而增大;扩挖宽度为1.5~2.5 m时的最优锚杆长度和间距分别为2.5 m和1.7 m,扩挖宽度为3.5~4.5 m时二者分别为3.0 m和1.2 m.

膨胀性泥岩铁路隧道变形机理与仰拱底鼓控制技术研究

为揭示膨胀性泥岩铁路隧道仰拱底鼓变形机理并提出对应控制措施,以西(宁)至成(都)铁路膨胀性泥岩隧道为背景,采用室内试验、数值模拟、案例调研等方法开展研究。结果发现:膨胀性泥岩在浸水后物理力学参数明显降低,随着浸水时间增加,降低速率逐渐减小,其膨胀系数为4.8%;FLAC3D中的应变软化模型通过湿度应力场与温度应力场的转化能较好模拟膨胀性泥岩浸水后的参数衰减效应,当初始含水率分别为5%、15%、25%时,膨胀力试验结果分别为37.84,123.90,189.06kPa;随着水位上升,隧周孔隙水压力逐渐增大,当地下水位分别为Z=-5 m、Z=0 m、Z=5 m、Z=10 m、Z=15 m、Z=30 m时,隧周最大孔隙水压力分别为0,100,125,200,250,350 kPa,仰拱底部随软化系数的增加由沉降逐渐变为隆起,隧底围岩软化及上部挤压造成的剪切破坏是仰拱底鼓的最大诱因;随着仰拱矢跨比增加,二次衬砌弯矩减小,拱底和墙脚位置二次衬砌弯矩减小值较大,因此仰拱底部受力得到优化;适当提高仰拱矢跨比,采用全环钢架+钢筋混凝土衬砌、加强基底排水、采用基底换填或管桩加固等措施是膨胀性泥岩铁路隧道设计关键。

纤维膨胀剂对隧道衬砌混凝土性能的影响

研究纤维膨胀剂对不同水胶比和不同强度等级混凝土工作性能、抗压强度和变形性能的影响。结果表明,相同水胶比条件下,纤维膨胀剂掺量对混凝土拌合物坍落度无明显影响;纤维膨胀剂掺量是影响混凝土限制膨胀率的主要因素,纤维膨胀剂掺量由7%增加至11%能更有效地补偿收缩;但纤维膨胀剂掺量增加,在提高补偿收缩能力的同时,也会降低混凝土抗压强度。综合考虑纤维膨胀剂对混凝土抗压强度和限制膨胀率的影响后,确定C30、C40强度等级的隧道衬砌膨胀混凝土配合比,经验证该配合比下混凝土工作性能良好、满足强度设计要求,且均有良好的早期抗裂性能。