Stability evaluation method of large cross-section tunnel considering modification of thickness-span ratio in mechanized operation

Purpose-This study aims to research the large cross-section tunnel stability evaluation method corrected after considering the thickness-span ratio.Design/methodology/approach-First,taking the Liuyuan Tunnel of Huanggang-Huangmei High-Speed Railway as an example and taking deflection of the third principal stress of the surrounding rock at a vault after tunnel excavation as the criterion,the critical buried depth of the large section tunnel was determined.Then,the strength reduction method was employed to calculate the tunnel safety factor under different rock classes and thickness-span ratios,and mathematical statistics was conducted to identify the relationships of the tunnel safety factor with the thickness-span ratio and the basic quality(BQ)index of the rock for different rock classes.Finally,the influences of thickness-span ratio,groundwater,initial stress of rock and structural attitude factors were considered to obtain the corrected BQ,based on which the stability of a large cross-section tunnel with a depth of more than 100 m during mechanized operation was analyzed.This evaluation method was then applied to Liuyuan Tunnel and Cimushan No.2 Tunnel of Chongqing Urban Expressway for verification.Findings-This study shows that under different rock classes,the tunnel safety factor is a strict power function of the thickness-span ratio,while a linear function of the BQ to some extent.It is more suitable to use the corrected BQ as a quantitative index to evaluate tunnel stability according to the actual conditions of the site.Originality/value-The existing industry standards do not consider the influence of buried depth and span in the evaluation of tunnel stability.The stability evaluation method of large section tunnel considering the correction of overburden span ratio proposed in this paper achieves higher accuracy for the stability evaluation of surrounding rock in a full or large-section mechanized excavation of double line high-speed railway tunnels.

The effects of beam drifts on elastic scattering measured by the large solid-angle covered detector array

A new detector array characterized by compact structure and large solid-angle coverage was designed for radioactive ion beam(RIB)experiments and measuring multi-particle correlations.A Monte Carlo simulation was performed to explore the effects of beam drifts in different directions and distances on the angular distribution of the Rutherford scattering,as measured by the detector array.The results indicate that when the beam drift distance is less than 2.0 mm,the symmetry of the detector array can maintain a count error of less than 5%.This confirms the property of the detector array for RIB experiments.Furthermore,the simulation was validated through the elastic scattering angular distributions of 6;7 Li measured by the detector array in 6;7Li t209 Bi experiments at different energies.

Comprehensive Marine Observing Experiment Based on High-Altitude Large Unmanned Aerial Vehicle(South China Sea Experiment2020 of the “Petrel Project”)

In collaboration with 12 other institutions, the Meteorological Observation Center of the China Meteorological Administration undertook a comprehensive marine observation experiment in the South China Sea using the Yilong-10 high-altitude large unmanned aerial vehicle(UAV). The Yilong-10 UAV carried a self-developed dropsonde system and a millimeter-wave cloud radar system. In addition, a solar-powered unmanned surface vessel and two drifting buoys were used. The experiment was further supported by an intelligent, reciprocating horizontal drifting radiosonde system that was deployed from the Sansha Meteorological Observing Station, with the intent of producing a stereoscopic observation over the South China Sea. Comprehensive three-dimensional observations were collected using the system from 31 July to2 August, 2020. This information was used to investigate the formation and development processes of Typhoon Sinlaku(2020). The data contain measurements of 21 oceanic and meteorological parameters acquired by the five devices, along with video footage from the UAV. The data proved very helpful in determining the actual location and intensity of Typhoon Sinlaku(2020). The experiment demonstrates the feasibility of using a high-altitude, large UAV to fill in the gaps between operational meteorological observations of marine areas and typhoons near China, and marks a milestone for the use of such data for analyzing the structure and impact of a typhoon in the South China Sea. It also demonstrates the potential for establishing operational UAV meteorological observing systems in the future, and the assimilation of such data into numerical weather prediction models.

Mechanism and practice of rock control in deep large span cut holes

Deep large span cut holes are difficult to stabilize. The 7801 cut hole in the Lu'an Wuyang Mine was used as this project's background. The main factors affecting large span cut hole stability are analyzed. Pre- stressed bolting theory was used to design a roof control method for a large span roadway. By reducing the span and applying equal strength coordinated supports the rock could be stabilized. The control prin- ciples and methods are given herein along with the analysis. A double micro arch cross section roadway is defined and its use in solving the current problem is described. Beam arch theory was used to build a model of the double micro arch cross section roadway. A support reverse force model for the arch foot intersection was also derived. A support method based upon reducing the width of the large span in the cut hole is presented. These results show that the reduced span of the roadway roof plus the use of cable anchors and single supports gives an effective way to control the large span cut hole. On site monitoring showed that the reduced span support from the double micro arch cross section roadway design had a significant effect. The roadway surface displacement was small and harmful deformation of the cut hole was effectively controlled. This will ensure its long term stability.

凤凰山特大断面黄土隧道五步单侧壁导坑法研究

为解决特大断面黄土隧道采用双侧壁导坑法施工进度慢、成本高的问题,以G30连霍高速公路清水驿至忠和段扩容改造工程凤凰山隧道为背景,提出五步单侧壁导坑法。通过数值模拟对比分析双侧壁导坑法、五步单侧壁导坑法、传统单侧壁导坑法和台阶法在施工过程中的围岩变形及钢拱架应力,并结合现场试验段监测数据验证特大断面凤凰山隧道采用五步单侧壁导坑法施工的可行性。结果表明:1)五步单侧壁导坑法拱顶沉降和水平收敛比传统单侧壁导坑法分别减小3.59 cm和1.31 cm,比双侧壁导坑法分别增大1.4 cm和0.59 cm;钢拱架应力除拱肩外均小于双侧壁导坑法,最大处减少了70 MPa,钢拱架应力最大值与钢材屈服强度的比值比双侧壁导坑法增大0.04,比单侧壁导坑法减小0.08。2)传统单侧壁导坑法的安全性小于五步单侧壁导坑法,改进后的五步单侧壁导坑法相比双侧壁导坑法能在控制围岩变形的同时加快施工进度,降低施工成本。3)五步单侧壁导坑法中隔壁的最优位置应结合具体工程情况进行单独优化计算,针对本工程而言,其最优位置为45%洞宽。

基于LQR的船舶自主靠泊策略研究

自主靠泊是船舶自动航行研究领域的热点。为有效解决船舶靠泊过程中的路径规划与控制问题,提出了一种基于Frenet框架的改进线性二次型调节器(LQR)控制方法和一种自适应的靠泊策略决策模型,将船舶运动控制、路径规划和靠泊策略选择相结合,实现船舶的自适应自主靠泊。首先,建立风流干扰的船舶动力学模型,根据当前风流环境与泊位的空间关系自动选择靠泊方式;然后,规划靠泊路径并利用LQR控制器实现船舶的自主靠泊。为验证控制器的有效性,在仿真实验中充分考虑靠泊过程中的船舶大漂角特性与岸壁效应。仿真实验表明:本文提出的方法对环境干扰具有良好的鲁棒性,能够根据不同工况选择不同的靠泊策略并实现船舶的自主靠泊。

特厚煤层大断面顺槽快速掘进支护技术研究

在分析龙王沟煤矿61612工作面主运特厚煤层大断面顺槽地质和生产条件的基础上,研究其支护要点,根据地质条件和支护要点,提出快速掘进配套原则,选取快速掘进设备。采用理论计算和数值模拟的方法,对多种支护方案进行比较,提出配套的锚杆锚索支护设计和施工方案。井下试验表明,采用快速掘进设备和配套的快速支护设计,实现了快速掘进支护,大幅提高掘进速度。矿压监测结果表明,特厚煤层大断面顺槽支护效果很好。

转载式防飘带装置在倾角巷道带式输送机中应用

赵庄煤矿四采区回风巷上山掘进期间巷道倾角大,安装传统SSJ型带式输送机进行煤矸运输时出现严重“飘带”现象,制约了巷道煤矸安全高效运输。针对这一问题,分析了传统安装压带轮和多部输送机搭接等方案,设计了一套转载式防飘带装置。通过实际应用效果来看,该装置投入使用后成功解决了大倾角巷道带式输送机“飘带、跑偏”等技术难题,取得了显著应用成效。

CFD-Based Numerical Analysis of a Variable Cross-Section Cylinder

Using ANSYS-CFX, a general purpose fluid dynamics program, the vortex-induced vibration(VIV) of a variable cross-section cylinder is simulated under uniform current with high Reynolds numbers. Large eddy simulation(LES) is conducted for studying the fluid-structure interaction. The vortex shedding in the wake, the motion trajectories of a cylinder, the variation of drag and lift forces on the cylinder are analyzed. The results show that the vortices of variable cross-section cylinder are chaotic and are varying along the cylinder. In places where cross-sections are changing significantly, the vortices are more irregular. The motion trail of the cylinder is almost the same but irregular. The drag and lift coefficients of the cylinder are varying with the changes of diameters.

Drift Control Technology Using Wire-Suspension for the Airgun Source Platform in Qilian Mountain

There are several key issues in dynamic monitoring of subsurface structures,such as signal-to-noise ratio( SNR),repeatability of seismic sources and accurate measurement of velocity. Using a large volume airgun source,we constructed a high-performance active system which mainly consists of airgun excitation and signal reception. In order to reduce the platform drift from the shot position,we put forward the platform drift control technique. Experimental results show that the technique can effectively solve the problem of platform drift from the set position under fluid impact after airgun excitation. The results of this study can be a reference for repeated airgun source detection at certain excitation sites.

Scattering of Electromagnetic Waves by Drift Vortex in Plasma

In a quasi-two-dimensional model, the scattering of incident ordinary electromag- netic waves by a dipole-electrostatic drift vortex is studied with first-order Born approximation. The distribution of the scattering cross-section and total cross-section are evaluated analytically in different approximate conditions, and the physical interpretations are discussed. When the wavelength of incident wave is much longer than the vortex radius （kia〈〈1）, it is found that the angle at which the scattering cross-section reaches its maxim depends significantly on the approximation of the parameters of the vortex used. It is also found that the total scattering cross-section has an affinitive relation with the parameters of the plasma, while it is irrelevant to the frequency of the incident wave in a wide range of parameters of the vortex. In a totally different range of parameters when incident wave is in the radar-frequency range （then kia 〈〈 1, the wavelength of incident wave is much shorter than the vortex radius）, the numerical procedure is conducted with computer in order to obtain the distribution and the total expression of the scattering crosssection. Then it is found that the total scattering cross-section in the low frequency range is much larger than that in high frequency range, so the scattering is more effective in the low frequency range than in high frequency range.

情境流驱动的大规模在线学习动态分组方法

在大规模在线学习社区中,学习者的行为特征可能会随时间发生变化,如何根据个体和群体的动态演化特征实现学习小组的自适应动态划分,是有效开展协作学习的关键。为此,文章提出一种情境流驱动的大规模在线学习动态分组方法:首先,构建基于活动理论的学习者情境模型,将反映情境指标的多模态数据转化为情境流;然后,扩展模糊C均值聚类算法,使用增量式流处理和动态滑动窗口技术检测概念漂移,实现基于某一情境维度的学习群体自适应动态聚类;最后,对不同情境维度的同质聚类结果进行差异化组合,得到异质学习小组。实验证明,动态分组在合作倾向、互惠性、群体互动一致性等方面比静态分组更具优势。文章的研究可为在线学习平台智能分组提供方法指引,并为实现有效的在线协作学习提供支撑。

非一致地震波动输入下大型钢筋混凝土框架结构-地基体系地震响应规律

为探索非一致地震波动输入对大型钢筋混凝土框架结构地震响应的影响,基于OpenSees软件平台建立二维钢筋混凝土框架结构-地基动力相互作用有限元模型。将El-Centro地震波按P波波形分别以0°、15°、30°和35°角入射该有限元模型进行计算,对比分析框架柱内力和楼层层间位移的地震响应。研究发现非一致地震波输入方法对于大型钢筋混凝土框架结构建筑动力响应影响明显,随着地震波入射角的增大,钢筋混凝土框架结构底层柱的轴力幅值减小,剪力幅值增大,而弯矩幅值变化较小,楼层层间位移幅值也随之增大。研究结果对于大型钢筋混凝土框架结构抗震设计具有参考意义。

OBLIQUE TOWING TEST AND MANEUVER SIMULATION AT LOW SPEED AND LARGE DRIFT ANGLE FOR DEEP SEA OPEN-FRAMED REMOTELY OPERATED VEHICLE

This article presents the newly designed oblique towing test in the horizontal plane for the scaled model of 4 500 m deep sea open-framed Remotely Operated Vehicle （ROV）,which is being researched and developed by Shanghai Jiao Tong University.Accurate hydrodynamics coefficients measurement is significant for the maneuverability and control system design.The scaled model of ROV was constructed by 1：1.6.Hydrodynamics tests of large drift angle were conducted through Large Amplitude Horizontal Planar Motion Mechanism （LAHPMM） under low speed.Multiple regression method is adopted to process the test data and obtain the related hydrodynamic coefficients.Simulations were designed for the horizontal plane motion of large drift angle to verify the coefficients calculated.And the results show that the data can satisfy with the design requirements of the ROV developed.

Analytical study on pretensioned bolt-cable combined support of large cross-section tunnel

To study the mechanical responses of large cross-section tunnel reinforced by pretensioned rock bolts and anchor cables, an analytical model is proposed. Considering the interaction between rock mass and bolt-cable support, the strain softening characteristic of rock mass, the elastic-plastic characteristic of bolt-cable support, and the delay effect of installation are considered in the model. To solve the different mechanical cases of tunneling reinforced by bolt-cable support, an analytical approach has been put forward to get the solutions of stress and displacement associated with tunneling. The proposed analytical model is verified by numerical simulation. Moreover, parametric analysis is performed to study the effects of pretension force,cross-section area, length, and supporting density of bolt-cable support on tunnel reinforcement, which can provide references for determining these parameters in tunnel design. Based on the analytical model, a new Ground Response Curve(GRC)considering the reinforcement of bolt-cable support is obtained, which shows the pretension forces and the timely installation are important in bolt-cable support. In addition, the proposed model is applied to the analysis of the Great Wall Station Tunnel, a high-speed railway tunnel with a super large cross-section, which shows that the analytical model of bolt-cable support was a useful tool for preliminary design of large cross-section tunnel.

轨道交通大断面深埋隧道施工工法——扩大拱脚台阶法

为适应轨道交通建设的新环境、新形势,结合重庆主城区地形地貌、地质条件和轨道交通车站特点,提出一种新的大断面深埋轨道交通车站隧道的施工工法——扩大拱脚台阶法。该工法以新奥法为基本理论依据,充分发挥围岩的自稳能力和开挖面的空间约束作用,通过初支大拱脚的设置,将拱部荷载传递至拱脚围岩,从而提高拱部初期支护的承载能力和稳定性。同时,通过分台阶分步开挖,能够为大断面隧道开挖提供充足的施工作业空间,有效提高隧道的施工工效,节约工程投资、缩短工期。以重庆轨道交通9号线红岩村站为例,对该工法与双侧壁导坑法进行对比分析。通过理论计算分析,可以得出扩大拱脚台阶法对围岩的扰动更小,更有利于对围岩的保护和变形控制,工程风险更加可控。

Investigate the nonuniformity of low-energy electron beam with large cross-sections

Over the past decades, low-energy electron accelerators have been used worldwide for surface curing and sterilization. The beam nonuniformity is an important parameter of the low-energy electron beam with large cross-sections. A simple and accurate measurement system of nonuniformity for the low-energy electron beam with large cross-sections was developed. The main concept consists in the measurement of nonuniformity, which is realized by using a linear actuator to drive two scanning wires through the beam's cross-sections at a fixed speed. The beam distribution can be obtained by sending/collecting the current signals to/from the Data Acquisition (DAQ) software on a laptop by a USB DAQ card. This device is very convenient for the performance testing of a new accelerator at the manufacturer's site. The distribution of the homemade low voltage electron accelerator EBS-300-50 was measured and evaluated.

低轨大规模卫星星座内部防碰撞安全性分析

针对低轨大规模星座卫星间碰撞安全问题,对星座构型的最大漂移量开展了研究。基于球面三角形理论计算了卫星轨道平面的最小相位差;采用控制变量法对星座构型参数进行研究,分析不同构型参数对星座卫星最小相位差的影响,以及升交点赤经漂移量与最小相位差的关系,提出了基于最小相位差的星座构型参数协同设计方法;基于相对相位分析方法,建立升交点赤经漂移量与相位漂移量随时间变化的函数关系;最后,以Starlink第一期星座为参考对象进行仿真,验证了构型参数协同设计方法的合理性。

大断面综采工作面切眼掘进一次成巷技术研究

为了解决矿井大断面掘进巷道支护难度大现状,依据工程实例,针对大断面综采工作面切眼掘进一次成巷技术进行分析,从而提高巷道作业功率,以及掘进速度,保证后续开展操作顺利进行。

大型油轮稳泊安全风险分析及对策措施探讨

介绍了大型油轮稳泊主要安全风险类型,分析了大型油轮在停泊作业期间水文、气象、码头结构、油轮设备设施等因素对稳泊安全的影响,并结合多起油轮断缆、漂移事故经验,提出针对性的大型油轮稳泊安全对策措施。