长江下游特拉锚垫防护结构下土质岸坡稳定性研究

玉带洲位于长江下游段,岸坡后方存在大型湖泊,坡后渗流问题较为严重。为确保岸坡安全,提高岸坡整体稳定性,减少水土流失量,需要对岸坡进行合理的防护处理。通过物理模型分别模拟岸坡在特拉锚垫防护结构、裸土段的渗流情况进行对比试验,设置若干观测点,运用MATLAB软件绘制岸坡渗流前后三维地形图,观测岸坡设置点的位移情况。结果表明,渗流后有特拉锚垫防护结构的观测点最大位移量为2 cm,裸土段最大位移量为5.1 cm;特拉锚垫段渗流前后的地形图趋于吻合,说明特拉锚垫对于坡后渗流有较好的防护效果。     

混凝土联锁块护底软体排抗掀稳定分析

针对规范中软体排抗掀稳定计算公式未考虑水深影响的问题,对水流作用下混凝土联锁块软体排受力进行研究。采用理论推导方法,得出了新的混凝土联锁块软体排抗掀稳定计算公式,结合数模分析确定新公式的相关参数取值。新公式中考虑了水深的影响,采用临界断面平均流速替代规范公式的软体排边缘临界流速,较规范公式更为准确。分别采用新公式和规范公式对黑沙洲水道航道整治二期工程护底软体排抗掀稳定进行计算。分析结果表明:新公式较规范公式更能反映软体排实际受力情况。工程实践证明新公式具有较好的可靠性,可供类似工程参考和借鉴。     

基于扁拱突变理论的路基下伏溶洞顶板稳定性分析

根据路基下伏溶洞受荷体系的力学特性,将结构体系简化为两端固定铰支的扁拱模型;基于突变理论推导得到扁拱的能量势函数和分叉集方程,从而建立了路基下伏溶洞顶板突变模型平衡曲面;根据溶洞顶板突变失稳的条件,提出了确定路基下伏溶洞顶板的极限承载力及最小安全厚度的方法;并对溶洞顶板厚度h、溶洞顶板跨径l、溶洞顶板失高f、岩层的弹性模量E、溶洞顶板上覆荷载q五个影响因素进行参数分析,可得如下结论:溶洞顶板的极限承载力随着溶洞顶板厚度的增加,溶洞顶板失高的增加、岩层弹性模量的增加而增加,随着溶洞顶板跨径、溶洞顶板上覆荷载的增加而减小.     

重力式锚碇抗滑移稳定性设计参数敏感性分析

以重力式锚碇设计方案为背景,对影响锚碇抗滑动稳定性的设计参数开展了敏感性分析,识别出其中对锚碇稳定性具有显著控制性的设计参数.此外,对作用于锚碇主缆缆力的主要影响参数进行了敏感性分析.分析结果可以为重力式锚碇的设计优化提供一些基础数据,并为挖掘锚碇设计空间提供技术支撑.     

大跨度软岩公路隧道短台阶七步平行流水作业施工技术

大跨度软岩公路隧道采用短台阶七步平行流水作业法施工在我国尚属探索阶段，结合工程实践，结合工程实践，详细地介绍了该施工方法的技术特点。适用范围、工艺原理、施工工艺、机具设备、劳力组织、质量控制、施工安全以及效益分析等，对类似隧道施工有一定的参考价值。     

Loss of stability of a railway wheel-set,subcritical or supercritical

Most researches on railway vehicle stability analysis are focused on the codimension 1 (for short, codim 1) bifurcations like subcritical and supercritical Hopf bifurcation. The analysis of codim 1 bifurcation can be completed based on one bifurcation parameter. However, two bifurcation parameters should be considered to give a general view of the motion of the system when it undergoes a degenerate Hopf bifurcation. This kind of bifurcation named the generalised Hopf bifurcation belongs to the codimension 2 (for short, codim 2) bifurcations where two bifurcation parameters need to be taken into consideration. In this paper, we give a numerical analysis of the codim 2 bifurcations of a nonlinear railway wheel-set with the QR algorithm to calculate the eigenvalues of the linearised system incorporating the Golden Cut method and the shooting method to calculate the limit cycles around the Hopf bifurcation points. Here, we found the existence of a generalised Hopf bifurcation where a subcritical Hopf bifurcation turns into a supercritical one with the increase of the bifurcation parameters, which belong to the codim 2 bifurcations, in a nonlinear railway wheel-set model. Only the nonlinear wheel/rail interactive relationship has been taken into consideration in the lateral model that is formulated in this paper. The motion of the wheel-set has been investigated when the bifurcation parameters are perturbed in the neighbourhood of their critical parameters, and the influences of different parameters on critical values of the bifurcation parameters are also given. From the results, it can be seen that the bifurcation types of the wheel-set will change with a variation of the bifurcation parameters in the neighbourhood of their critical values.     

The effect of wheel set gyroscopic action on the hunting stability of high-speed trains

This study explores the effects of wheel set gyroscopic action on hunting stability by calculating linear and nonlinear critical speeds. First, a dynamic model for a high-speed vehicle with 23 degrees of freedom is developed by considering wheel set gyroscopic action. The linear and nonlinear critical speeds are calculated by eigenvalue analysis and drawing a bifurcation map, respectively. Two computer programs for linear and nonlinear stability analysis are developed. Second, based on an actual high-speed vehicle in China, the effects of wheel set gyroscopic action on hunting stability are quantitatively investigated using computer simulation. Furthermore, the difference between the effects of gyroscopic moments about the x-axis and z-axis is discussed. The results show that the moment about the x-axis is harmful to hunting stability, but the moment about the z-axis is beneficial to hunting stability. However, the integrated effect of these two moments can enhance the critical speeds and suppress the hunting motion.     

基于ASIFT与RANSAC算法的岩体结构三维重建方法研究

隧道开挖过程中岩体结构面信息获取的快慢和准确程度直接影响隧道施工的安全,针对三维重建算法效率低的问题,提出一种基于ASIFT与RANSAC算法的岩体结构三维重建方法和策略。首先采用普通数码相机快速获取一系列真实描述岩体结构的数字影像;然后针对岩体影像比例尺与倾斜角变化大、纹理相对贫乏的特点,采用ASIFT匹配算法与RANSAC误匹配点剔除算法来保证立体影像之间稀疏匹配的效率和可靠性;最后采用光束法联合平差方法对系列影像之间的相对位置与姿态进行求解,并综合利用核线几何约束、半全局匹配、多视最小二乘匹配等策略实现岩体影像的密集匹配,最终提取出岩体的三维信息。工程实践表明:基于ASIFT与RANSAC算法的岩体结构三维重建方法可以方便地实现工程岩体结构面完全非接触式测量,有效提高测量效率,避免测量人员暴露于未支护岩体下的危险。     

昔格达地层隧道围岩及初期支护变形规律研究

为探明昔格达地层隧道开挖过程中初期支护背后空隙注浆的时机以及预留变形量的大小,以成昆复线铁路昔格达地层隧道为背景,采用现场实测与统计分析的方法对昔格达地层隧道围岩和初期支护的变形规律以及预留变形量进行深入分析。研究结果表明:1)昔格达地层隧道上台阶开挖后初期支护与围岩间存在初始空隙,拱顶围岩与初期支护间的差异沉降为1~2 mm,受地质、埋深及施工等因素影响,中台阶开挖较易引起隧道塌方,建议中台阶开挖前对拱部初期支护背后的空隙进行注浆回填。2)昔格达地层隧道预留变形量可根据掌子面施工揭示围岩情况调整,若施工揭示的昔格达组以页岩为主,建议预留变形量设置为24~30 mm;若施工揭示的昔格达组以砂岩为主,建议预留变形量设置为118~123 mm。     

基于RMR岩体分级系统的TBM掘进性能参数预测

为解决由于地质条件原因造成TBM掘进效率低下的问题,基于吉林引松供水工程建立的TBM数据库,提出应用RMR岩体分级系统对TBM的掘进性能参数进行预测。通过回归分析的方法分别建立了RMR与TBM性能预测参数掘进速率(PR)、施工进度(AR)、利用率(U)以及贯入度指数(FPI)的经验公式。研究结果表明:RMR与PR、AR、U均呈现二次相关关系,RMR与FPI为线性关系,且相关系数均大于0.7;当RMR=50~70时,岩体具有较好的可掘性;当岩体条件较差(RMR30~40)或者岩体条件极好(RMR70~80)时,岩体的可掘性均较差;吉林引松工程TBM掘进的平均利用率为22.36%,与地质条件相关的停工时间约占总工期的25.97%。