Numerical modeling of large deformation and nonlinear frictional contact of excavation boundary of deep soft rock tunnel

Roadways excavated in soft rocks at great depth are difficult to be maintained due to large deformation of surrounding rocks, which greatly influences the safety and efficiency of deep resources exploitation. During the excavation process of a deep soft rock tunnel, the rock wall may be compacted due to large deformation. In this paper, the technique to address this problem by a two-dimensional (2D) finite element software, large deformation engineering analyses software (LDEAS 1.0), is provided. By using the Lagrange multiplier method, the kinematic constraint of non-penetrating condition and static constraint of Coulomb friction are introduced to the governing equations in the form of incremental displacement. The numerical example demonstrates the efficiency of this technology. Deformations of a transportation tunnel in inclined soft rock strata at the depth of 1 000 m in Qishan coal mine and a tunnel excavated to three different depths are analyzed by two models, i.e. the additive decomposition model and polar decomposition model. It can be found that the deformation of the transportation tunnel is asymmetrical due to the inclination of rock strata. For extremely soft rock, large deformation can converge only for the additive decomposition model. The deformation of surrounding rocks increases with the increase in the tunnel depth for both models. At the same depth, the deformation calculated by the additive decomposition model is smaller than that by the polar decomposition model.

Point-contact tunneling spectroscopy between a Nb tip and an ideal topological insulator Sn-doped Bi1.1Sb0.9Te2S

The lightly Sn-doped Bi1.1Sb0.9Te2S is a good material to investigate the pure topological surface state because the bulk bands are far away from the Fermi level. By measuring point-contact tunneling spectra on the topological insulator Bi1.08Sn0.02Sb0.9Te2S samples with a superconducting Nb tip, we observed the suppression of differential conductance near zero bias, instead of the enhancement due to Andreev reflection on the spectra. The fitting to the measured spectrum results in a superconducting gap of more than 4 meV, and this value is much larger than the superconducting gap of the bulk Nb. The gaped feature exists at temperatures even above the critical temperature of bulk Nb, and is visible when the magnetic field is as large as 9 T at 3 K. We argue that such behaviors may be related to the pressure induced superconductivity by the tip in the junction area, or just some novel phenomena arising from the junction between an s-wave superconductor and an ideal topological insulator.

Transition from tunneling regime to local point contact realized on Ba0.6K0.4Fe2As2 surface

Using scanning tunneling spectroscopy, we studied the transition from tunneling regime to local point contact on the iron-based superconductor Ba0.6K0.4Fe2As2. By gradually reducing the junction resistance, a series of spectra were obtained with the characteristics evolving from single-particle tunneling into Andreev reflection. The spectra can be well fitted to the modified Blonder–Tinkham–Klapwijk（BTK） model and exhibit significant changes of both spectral broadening and orbital selection due to the formation of point contact. The spatial resolution of the point contact was estimated to be several nanometers, providing a unique way to study the inhomogeneity of unconventional superconductors on such a scale.

Non-contact monitoring and analysis system for tunnel surrounding rock deformation of underground engineering

It is very important to monitor surrounding rock deformation in tunnel construction. The principle, function, development and application of the system composed of a total station and computer for monitoring and analyzing surrounding rock deformation were discussed. The new methods of two free station of 3D measurement and its mathematic adjustment mode were presented. The development of software for total station on-board and post for computer were also described. Without centering it and measuring its height, the total station controlled by the software on-board can fulfill the whole measurements to target points. Monitoring data can be processed by the post software and results of regression analysis, forecasting information of the tunnel surrounding rock deformation can be provided in time. The practical use shows that this system is practicable, highly accurate and efficient. It satisfies the needs of safety and information construction in tunnel construction of underground engineering.

隧道围岩-衬砌接触面剪切特性模拟研究

探究隧道围岩-衬砌接触面在不同法向应力及不同粗糙度条件下的剪切特性规律,对进一步研究隧道围岩与衬砌间的相互作用及岩体稳定性具有重要的理论和工程意义。为考虑粗糙度条件,利用分形理论,通过改变分形公式中的分形维数D及分形粗糙度G生成5种不同接触面,基于二维颗粒流程序(PFC^(2D)),建立接触面数值剪切模型,尺寸为150 mm×150 mm。开展同一接触面在不同法向应力下,数值模拟剪切试验及不同接触面在同一法向应力下的数值模拟试验;将数值剪切试验与室内剪切试验获得的剪切应力-剪切位移曲线进行对比,验证数值剪切模拟的可靠性。研究结果表明:(1)数值模型剪切破坏产生的裂隙主要集中于中间接触面处,破坏后的应力主要集中于接触面粗糙度最大处,破坏裂纹可分为剪切裂纹和张拉裂纹,其中张拉裂纹占主要优势;(2)剪切应力-剪切位移过程曲线存在爬坡、啃断、滑移三大阶段,具有明显的峰值强度和残余强度,法向位移随着剪切位移的增加而增大,产生剪胀效应;(3)随着法向应力增加,剪切和张拉裂纹数量增加,破坏现象越明显,峰值强度和残余强度增大,剪胀效应减小;(4)随着粗糙起伏度增大,即分形维数D的增大或者分形粗糙度G的减小,破坏裂纹数量增加,其中张拉裂纹增加较明显,峰值强度和残余强度增大,剪胀效应增大。

基于加州承载比试验的隧道弃渣颗粒接触力场形状影响因素分析

对级配碎石而言,不同的颗粒表面性质会影响颗粒接触力场形状、大小及梯度,进而改变试样所受约束力。分析加州承载比(California bearing ratio,CBR)试验过程中试样侧板及底板的受力演变,探究试样颗粒细观参数对试样颗粒接触力场及试样约束力的影响。通过对比不同刚度比、摩擦系数与黏结强度(设定其比值为1下)对试样接触力场形状的影响。结果表明:以刚度比值6为界,随法向刚度的增大,颗粒接触力场长细比先增加后减小;随摩擦系数或黏结强度增大,接触力场长细比相应减小。考虑颗粒相对运动中黏结强度比中法向及切向参数作用不同,以黏结强度比4为界,随法向黏结强度增大,其接触力场长细比先增加后减小;随切向黏结强度增大,所得接触力场长细比变化趋势则为先减小后增加。研究成果可为研究隧道弃渣制成的级配碎石颗粒细观参数与其接触力场形状间关联性提供一定参考。

隧道盾构管片非接触式全周形貌测量方法研究

针对隧道盾构管片几何质量检测的需求,提出了非接触式全周形貌测量方法。首先,遥控移动载体移动至测点,投影仪投射散斑图像,工业相机捕获并计算得到的点云数据;然后,采集多个测点;最后,将各局部点云数据进行拼接,获得被测物体的全周形貌。该快速半自动的检测方法可获得隧道盾构管片全周尺寸,精度达到0.2%。

接触溶蚀条件下混凝土游离钙离子固化效果研究

为研究将硅灰和硅酸钠作为掺合料内掺后的喷射混凝土在接触溶蚀条件下析出钙离子的规律,在不同掺量下制备了单掺和复掺混凝土试块,开展30 d去离子水浸泡试验,测试溶液中的钙离子浓度、溶液pH值的变化情况,并结合SEM等微观检测对接触溶蚀过程进行研究。结果显示:单掺硅灰试块在不换水条件下的钙离子溶出量大大低于空白组,换水条件下30 d内3%、5%、7%掺量组较空白组平均溶出钙离子总重依次减少73.29%、69.65%、69.26%;单掺硅酸钠后,不换水条件下3%掺量的试块钙离子溶出量也能得到明显的降低,换水条件下30 d内1%、3%、5%掺量组较空白组平均溶出钙离子总重依次减少9.22%、20.53%、29.96%;将单掺组中固化效果良好的3%掺量硅灰和5%掺量硅酸钠复掺入混凝土后,不换水条件下浸泡溶液初始钙离子浓度仅为20~30 mg/L,从第18天左右溶液游离钙离子清零,换水条件下复掺试块较空白组平均溶出钙离子总重减少约85%。

隧道结构智能综合检测装备研制与应用

为解决隧道结构健康检测常规方式存在检测指标相对单一、机械化程度低、检测效率低、智能化水平低、安全风险高等突出问题,通过“非接触远距离检测”“表观病害智能检测与识别”“装备集成与智能控制”等关键技术研究与创新,研制出隧道结构智能综合检测装备,实现隧道结构内部病害、表观病害、结构形变等一体化综合检测。经工程验证,该装备可实现隧道衬砌厚度、背后空洞、钢拱架分布、衬砌裂缝、衬砌裂损、渗漏水、隧道断面及盾构法隧道椭圆度、管片错台等非接触高效综合检测,其综合作业效率为10~40 km/h,比常规检测方式提升2~8倍,检测方舱采用模块化设计,可搭载于轮式汽车底盘、轨道平板车等多种载体,适用于隧道建设施工过程中、竣工验收及运营期等多种工况,市场应用前景广阔。

理想化股骨隧道位置对ACL重建术后肌腱-骨界面愈合的影响

目的探讨前交叉韧带(ACL)重建术中理想化股骨隧道位置对术后肌腱-骨界面愈合的影响。方法选取61例行AMP单束解剖重建治疗的ACL断裂患者,其中,行理想化股骨隧道位置重建术(IDEAL)的患者为试验组(31例),行传统足印区中心点股骨隧道重建(MID)的患者为对照组(30例)。术中均利用股骨隧道尺进行测量,并记录不同组别患者术后6个月、12个月MRI检查结果;根据MRI信号强度结果将肌腱-骨界面的愈合程度分为5个等级,比较不同时间点患者肌腱愈合程度,并分析不同股骨隧道位置对术后肌腱-骨界面愈合的影响。结果61例患者均得到12月以上的随访,试验组患者股骨隧道长度长于对照组(P<0.05);且在术后6个月、12个月的肌腱-骨界面愈合过程中,试验组MRI结果显示肌腱愈合程度优于对照组(P<0.05)。结论理想化股骨隧道位置重建不仅可增加股骨隧道长度,侧面提高肌腱-骨界面的接触面积,同时可依靠其等距性促进肌腱-骨界面愈合,并加速康复进程。

基于隧道离心试验的柔性软接触土压计测试可靠性评价

开展一系列离心模型试验,选取线性误差、平均幅值误差、响应速率作为指标,基于隧道模型对柔性软接触新型土压计ESP-II和两种国际代表性传统土压传感器(PDA、EPL-D1)进行对比评价,验证新研发土压力计测量的可靠性。主要结论如下:①静力状态下,ESP-II、PDA、EPL-D1线性误差分别为19.36%,12.7%,21.0%,平均幅值误差为5.79%,48.2%,22.6%,证明ESP-II土压力计相比国际两种土压计具有较好静力测试性能。②动力荷载下,ESP-II、PDA、EPL-D1土压力计的平均响应速率分别为67.1,51.5,65.8 Hz,ESP-II的响应速率略高于其他两种土压力计,具有良好的响应频率;序列地震动荷载下ESP-II、PDA测得土压力与EPL-D1不同,呈现一致增量规律,而数值存在一定差异,反映土体具有较强结构性。③卸载过程中,3种土压力计测得数据均呈现不同程度的非线性变化特征,PDA和EPL-D1土压力时程曲线产生了偏折、跳变现象,而ESP-II土压力时程曲线保持了较好数据连续性,一定程度说明软接触式设计能实现土压力计与土体的良好接触。

富水海积砂层渗透注浆加固技术研究

富水海积砂层突水破坏是隧道建设极易诱发的地质灾害,不同的地质环境、注浆法浆液类别与海积砂层相互作用关系极为复杂。结合传统的水泥基浆液注浆施工工艺,综合运用半球形和柱形渗透扩散理论分析、模拟试验和现场监测等方法,研究富水砂层注浆扩散与加固机理,建立了注浆扩散范围与浆液对管片的压力的计算理论,并应用于特拉维夫市地铁联络隧道工程。研究结果表明:相较于冻结法,注浆法具有显著的经济效益。富水砂层扩散加固形式与砂层可注性与注浆压力相关,壁后注浆一般由渗透扩散向压密扩散的形式发展。在渗透阶段,半球形模型与柱形模型所揭示的浆液扩散规律基本一致,大小存在差异。浆液扩散半径主要取决于水泥基液中有效固体颗粒体积分数,当浆液体远离注浆口,浆液固体颗粒体积分数减小,浆液对土体孔隙的填充效果降低。浆液作用在隧道管片上的压力分布呈指数形式,沿注浆口径向急剧减小,后趋于平稳。

非对称异性隧道联络通道冷冻法施工技术

非对称异性隧道联络通道掘进时极易发生变形风险,因此对非对称异性隧道联络通道采取冷冻法加固施工技术。利用ANSYS软件,构建非对称异性隧道联络通道及其地层情况的三维模型,模拟不同冷冻天数、冷冻壁厚度、冷冻壁工况状以及冷冻温度下,联络通道的变形规律与稳定情况,并优化施工方案。结果表明:经冷冻法处理后的土体表现出良好的冻结效果,土体强度较高,掘进时土体不易塌陷;冷冻天数越长,位移变化量越小;土体冷冻壁较厚且全冷冻壁工况能够获得更加良好的加固效果;冷冻温度越低,联络通道越稳定。

全TOPCon电池正面多晶硅层硼掺杂工艺

为提升隧穿氧化层钝化接触(TOPCon)电池光电转换效率,本文通过高温扩散在n型TOPCon电池正面制作p型隧穿氧化层钝化接触结构,提升发射极钝化性能,减少正面金属复合。本文研究了不同沉积时间、推进温度、推进时间等工艺参数对实验样品钝化性能及掺杂曲线的影响。实验结果表明,当沉积时间为1500 s,推进温度为920℃,推进时间为20 min时,掺硼多晶硅层可获得较优的钝化性能及掺杂浓度,其中样品多晶硅层硼掺杂浓度达到1.40×10^(20)cm^(-3),隐开路电压(iV_(oc))大于720.0 mV。依据该参数制备的TOPCon电池光电转换效率可达23.89%,对应的短路电流密度为39.36 mA/cm^(2),开路电压(V_(oc))达到726.4 mV,填充因子(FF)为83.54%。

接触网隧道自动定位测量仪的研究设计

传统的隧道内吊柱安装位置测量方法采用全站仪、卷尺、激光测量仪、水准仪等仪器进行吊柱长度和底板角度的计算,这些测量方法存在测量效率低、测量精度差、数据记录多、人员需求多等问题。因此,设计出一种基于激光测距传感器的测量仪器,可消除多台测量仪器造成的误差,简化测量步骤,提高测量效率,缩减人工成本,保障接触网隧道内吊柱安装位置符合设计要求。

盾构隧道联络通道洞门复合管片修复技术

现有的管片堵漏技术为直接用快硬水泥浆封堵后,在其中埋入注胶管,后注入聚氨酯堵漏。该方法起效快速,但施工质量差,无法长时间抵御外部水压,后续维护成本高。文中介绍了一种盾构隧道联络通道洞门复合管片的堵漏修复技术,用于机械法施工的盾构隧道联络通道专用复合管片的修复,这种修复方法能够在狭小环境中精准定位管片渗流路径,缩小管片内覆钢板背部裂缝,且能够满足地铁隧道长时间运营的耐久性要求,能够为后续类似项目提供参考。

On the reverse leakage current of Schottky contacts on free-standing GaN at high reverse biases

In this work, a dislocation-related tunneling leakage current model is developed to explain the temperature-dependent reverse current–voltage（I–V –T） characteristics of a Schottky barrier diode fabricated on free-standing GaN substrate for reverse-bias voltages up to-150 V. The model suggests that the reverse leakage current is dominated by the direct tunneling of electrons from Schottky contact metal into a continuum of states associated with conductive dislocations in GaN epilayer.A reverse leakage current ideality factor, which originates from the scattering effect at metal/GaN interface, is introduced into the model. Good agreement between the experimental data and the simulated I–V curves is obtained.

Improving performances of ITO/GaP contact on AlGaInP light-emitting diodes

In this paper AlGaInP light emitting diodes with different types of electrodes： Au/Zn/Au-ITO Au/Ti-ITO Au/Ge/Ni-ITO and Au-ITO are fabricated. The photoelectricity properties of those LEDs are studied. The results show that the Au/Zn/Au electrode greatly improves the performance of LEDs compared with the other electrodes. Because the Au/Zn/Au electrode not only forms a good Ohmic contact with indium tin oxide （ITO）, but also reduces the specific contact resistances between ITO and GaP, which are 1.273× 10^-6 Ω·cm^2 and 1.743× 10^-3 Ω·cm^2 between Au/Zn/Au-ITO and ITO-GaP respectively. Furthermore, the textured Zn/Au-ITO/Zn electrode is designed to improve the performances of LEDs, reduce the forward-voltage of the LED from 1.93 to 1.88 V, and increase the luminous intensity of the LEDs from 126 to 134 mcd when driven at 20 mA.

Low contact resistivity between Ni/Au and p-GaN through thin heavily Mg-doped p-GaN and p-InGaN compound contact layer

Thin heavily Mg-doped InGaN and GaN compound contact layer is used to form Ni/Au Ohmic contact to p-GaN. The growth conditions of the compound contact layer and its effect on the performance of Ni/Au Ohmic contact to p-GaN are investigated. It is confirmed that the specific contact resistivity can be lowered nearly two orders by optimizing the growth conditions of compound contact layer. When the flow rate ratio between Mg and Ga gas sources of p＋＋-InGaN layer is 10.6% and the thickness of p＋＋-InGaN layer is 3 nm, the lowest specific contact resistivity of 3.98× 10-5 Ω cm2 is achieved. In addition, the experimental results indicate that the specific contact resistivity can be further lowered to 1.07 × 10-7Ω.cm2 by optimizing the alloying annealing temperature to 520 ℃.

Interaction of Twin Circular Shallow Tunnels in Soils—Parametric Study

In big and crowded cities with limited urban areas, it is sometimes necessary to build twin tunnels to overcome transportation problems. In a city like Riyadh in Saudi Arabia, tunneling becomes very essential to solve effectively traffic conjunctions and associated problems. The city started to construct big tunneling projects and it is expected in the near future to start building twin tunnels. If the design and construction process of twin tunnels are not understood and considered, damage to the tunnel lining or excessive ground surface settlement may take place. In this study, the interaction between adjacent tunnels excavated through soils in Saudi Arabia has been investigated using FE analysis and the range of the encountered soil properties. The investigation considered the effect of spacing between the twin tunnels and ground conditions on tunnel behavior. The analysis focused on the effect of constructing twin tunnels on ground surface settlement, contact pressure between lining and ground, and change in tunnel diameter. Based on the results obtained, it was observed that as the compressibility ratio, c, and spacing between tunnels decreased, the interaction effect between tunnels increased. For compressibility ratio of 0.01, the excavation of the new tunnel caused an increase in the lining deformation of the old one in the range of 0.1% to 0.3%. Furthermore, the excavation of the new tunnel leads to an increase in the contact pressure at the crown of the old one by 7% - 9%. At the spring line level, the excavation of the new tunnel had almost no effect on the far side of the old one. On the other hand, and for low compressibility ratio, the new tunnel excavation significantly affected contact pressure at the near side of the old one. For an expected tunnel life of 100 years, the results show an increase in the normalized contact pressure at the crown of the old tunnel due to the excavation of the new one in the range of 2% - 7% for compressibility ratio ranging between 0.01 - 0.1, respectively.