基于FBG(光纤光栅)监测技术的地铁盾构隧道环向变形研究

[目的]FBG(光纤光栅)监测技术具有动态响应快、抗干扰强、精度高、耐久性强等优点,能实现远距离实时监测,其反馈的环向变形监测数据对盾构掘进过程的参数调整有着重要意义,有必要基于光纤监测技术对管片环向变形规律进行深入研究。[方法]以某地铁隧道工程为例,采用光纤传感器对地铁隧道施工期管片进行实时监测。通过监测数据分析,研究管片施工环境中的环向应变变化规律,分析相对收敛位移与盾构掘进参数之间的相互关系。[结果及结论]监测数据表明,环向变形主要集中在管片安装之后的一周内和相邻隧道掘进的50 m范围内,当地层差且埋深小时,后掘进隧道对已施工管片收敛的影响程度为50%;当地层好且埋深大时,而后掘进隧道对已施工管片收敛的影响程度约为65%~83%。不同埋深时管片应变受土层及邻线隧道施工的影响较大,其中埋深小且土层差的管片变形变化大,埋深较大的管片约束性较好,变形变化不明显。相对收敛位移与盾构掘进参数存在明显的联系,盾构的总推力与管片的相对收敛位移存在负相关的关系,盾构的掘进速度与管片的相对收敛位移存在正相关的关系。采用FBG监测技术得到的实时监测数据,能作为盾构机掘进参数调整的依据。

铠装热电阻焊接新技术

本文研制了专用晶体管焊接电源并对铈钨电极进行激活处理,从而能在3～5A小电流下,可靠引燃电弧。采用新型焊枪喷嘴,增强氩气流对电弧的保护效果以及将铈钨电极端部磨削至合适的几何形状和尺寸,可提高小电流电弧的稳定性。

Analyses of axial,lateral and circumferential deformations of rock specimen in triaxial compression

The axial,lateral and circumferential strains were analyzed for a rock specimen subjected to shear failure in the form of a shear band bisecting the specimen in triaxial compression.Plastic deformation of the specimen stemmed from shear strain localization initiated at the peak shear stress.Beyond the onset of strain localization,the axial,lateral and circumferential strains were decomposed into two parts,respectively.One is the elas- tic strain described by general Hooke's law.The other is attributable to the plastic shear slips along shear band with a certain thickness dependent on the internal length of rock. The post-peak circumferential strain-axial strain curve of longer specimen is steeper than that of shorter specimen,as is consistent with the previous experiments.In elastic stage, the circumferential strain-axial strain curve exhibits nonlinear characteristic,as is in agreement with the previous experiment since confining pressure is loaded progressively until a certain value is reached.When the confining pressure is loaded completely,the circumferential strain-axial strain curve is linear in elastic and strain-softening stages.The predicted circumferential strain-axial strain curve in elastic and strain-softening stages agrees with the previous experiment.

局部凹陷对水下分离器极限承载力的影响

为了研究局部凹陷对水下分离器极限承载力的影响,以某无肋骨光壳深水水下分离器为研究对象,建立了含有局部缺陷的水下分离器圆柱壳有限元模型,分析了缺陷轴向长度、周向角度、缺陷深度及周向成对分布缺陷等因素对极限承载力的影响。分析结果认为,当缺陷轴向长度和周向角度一定时,随着深度幅值的增大,极限承载力下降明显;当缺陷深度和周向角度一定时,随着轴向长度的增大,极限承载力下降,其下降趋势趋于缓慢;当缺陷沿周向成对分布时,随着周向中心夹角的增大,圆柱壳的极限承载力呈驼峰曲线分布;当中心夹角相差90°时,极限承载力达到最大值。