系统自振对绝对重力仪的影响模式分析

隔振问题是绝对重力仪研制中的关键技术难题之一。在自主研制"小型mGal级绝对重力仪"过程中发现,除了需要克服地面振动的影响之外,系统自振的影响也不容忽视,最大能达到mGal量级。通过对研制样机实验观测结果的分析,研究了系统自振产生的原因以及对系统偏差与观测内符合精度的影响模式,并给出了改进方案,以消除"系统自振"的影响,提高研制仪器的观测精度。     

砾钢渣抗液化特性试验研究

陈化的钢渣作为土工回填材料是废弃钢渣循环利用的主要途径之一。按土的工程分类方法,将废弃钢渣划分为砾钢渣、粗钢渣和细钢渣。针对砾钢渣,考虑固结应力比、振动频率、围压和含砾量等影响因素开展动三轴试验研究。分析了砾钢渣的应力、应变和动孔隙水压力的特性,分析了砾钢渣试样的动强度与振动次数、动应变与振动次数、孔隙水压力与振动次数和动应力与动应变关系。采用Seed和Finn提出的饱和砂土动孔压计算模型分析砾钢渣的动孔压曲线类型,并与传统砂砾土的抗液化强度进行比较。得出砾钢渣的抗液化特性较好,工程中可以用砾钢渣替代传统的砂土、砂砾土、砂砾料和砂卵石作为回填料,解决砂砾资源日渐短缺的问题。     

超声波振动下不同应力条件对岩石强度影响的试验

振动有助于碎岩,以往关于振动碎岩机理的研究大多在低频率段展开。为填补超高频率段下振动碎岩机理的空白,采用单轴动静组合加载模式,开展了超声波振动下不同应力条件对岩石强度影响的试验研究,其中超声波振动频率为20kHz,预压范围为100～500N。研究结果表明:当预压小于200N时,岩石内部应力状态无法满足强度准则,岩石强度下降不明显;当预压大于等于200N时,岩石强度随振动时间的增加而逐渐降低且存在最优预压力值(400N)使得岩石强度最低。缩短振动频率与岩石固有频率的差值有利于提高超声波振动碎岩效率。     

浅谈挤密碎石桩的施工方法

挤密碎石桩施工法是一种振动成桩法,即先用桩管振动成孔,然后填入足够数量的碎石,最后振动密实成桩体。通过振动、挤密的成桩过程,将原地基土振动夯实,桩体与桩间土形成复合地基,达到既处理可液化地基又增强地基的效果。介绍了挤密碎石柱的施工方法和质量检测方法。     

基于GNSS-RTK的在建超高层风载动态变形监测

首先以海星达H32全能型GNSS-RTK接收机为试验仪器,进行不同星系组合的RTK定位精度试验研究。然后以在建的天津高银117大厦为监测对象,采用GPS+GLONASS+BDS三星系组合对其进行现场强风作用下的RTK动态变形监测。利用巴特沃斯滤波对实测数据进行去噪处理,得到各测点的位移曲线。分析结果表明:GPS单星系定位的平面坐标精度相对较差,双星系组合定位的平面坐标精度与三星系组合定位的平面坐标精度基本相当,但GPS+GLONASS+BDS三星系组合定位的稳定性和可靠性最强;由于施工阶段大厦结构的刚度和整体性与竣工后存在差异,故在强风作用下其按一定施工步距滞后的低矮外框的振动位移幅度大于其高耸内筒结构的振动位移幅度;大厦外框和内筒均存在横风向振动位移,且横风向振动位移与顺风向振动位移的大小相近;监测环境对监测结果有着一定的影响,66层各点的监测值误差要大于95层各点的监测值误差。     

对高斯投影与横轴墨卡托投影差异的研究

借助计算机代数系统Mathematica推导了较为严密的横轴墨卡托投影公式和高斯-克吕格投影公式,通过数值计算对二者进行了分析比较,证明由于公式推导思路和公式的结构不同,两种投影方法在较为严密的计算中还是存在一定的差异的。     

测量长周期回转波动的陀螺仪法

本文阐述了回转波动的陀螺仪法。内容包括陀螺仪法的工作原理、运动方程、测量方法、测量装置及其参数。     

Experimental evidence for flexibility of a building foundation supported by concrete friction piles

This article explores the possibility to measure deformations of building foundations from measurements of ambient noise and strong motion recordings. The case under study is a seven-storey hotel building in Van Nuys, California. It has been instrumented by strong motion accelerographs, and has recorded several earthquakes, including the 1971 San Fernando (M_L=6.6, R=22 km), 1987 Whittier–Narrows (M_L=5.9, R=41 km), 1992 Landers (M_L=7.5, R=186 km), 1992 Big Bear (M_L=6.5, R=149 km), and 1994 Northridge (M_L=6.4, R=1.5 km) earthquake and its aftershocks (20 March: M_L=5.2, R=1.2 km; 6 December, 1994: M_L=4.3, R=11 km). It suffered minor structural damage in 1971 earthquake and extensive damage in 1994. Two detailed ambient vibration tests were performed following the Northridge earthquake, one before and the other one after the 20 March aftershock. These included measurements at a grid of points on the ground floor and in the parking lot surrounding the building, presented and analyzed in this article. The analysis shows that the foundation system, consisting of grade beams on friction piles, does not act as a “rigid body” but deforms during the passage of microtremor and therefore earthquake waves. For this geometrically and by design essentially symmetric building, the center of stiffness of the foundation system appears to have large eccentricity (this is seen both from the microtremor measurements and from the earthquake recordings). This eccentricity may have contributed to strong coupling of transverse and torsional responses, and to larger than expected torsional response, contributing to damage during the 1994 Northridge, earthquake.     

打桩对周围建筑物振动影响的研究与实例分析

研究了打桩过程中土层质点振动速度的监测方法,打桩振动对周围建筑物影响程度的评价标准,并结合工程实例探讨了有关因素对检测结果的影响,及施工中应采取的相应减振措施。     

A study on seismic source process in short- term and imminent stage before destructive mining shock

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