露天采矿爆破振动对砌体结构破坏效应预测的Fisher判别模型及应用

 应用Fisher判别分析理论并结合工程实际特点,从爆破振动特征参量和砌体结构自身特性这2个方面出发,选取峰值质点振动速度(PPV)、爆破振动主频率、主频率持续时间、灰缝强度、圈梁构造柱、房屋高度、屋盖形式和砖墙面积率8个影响因素作为判别因子,建立爆破振动对砌体结构破坏效应预测的Fisher判别分析模型。将该方法应用到湖北一露天采场爆破振动对砌体结构破坏效应预测问题中,利用现场实测的108组数据进行训练和检验,回判估计的误判率为0.083,通过求解判别函数,认为峰值质点振动速度为最重要的判别指标,其后依次为圈梁构造柱、屋盖形式、砖墙面积率、房屋高度、爆破振动主频率、主频率持续时间和灰缝强度,可以为同类工程在选取爆破振动对砌体结构破坏效应的判别指标方面提供参考。利用其他12组现场数据作为预测样本进行测试,预测结果与实际情况吻合较好。研究表明,该方法回判估计的误判率低,判别性能良好,是爆破振动对砌体结构破坏效应预测的一种有效新方法,可以在实际工程中进行推广应用。     

水电工程爆破振动安全判据及应用中的几个关键问题

 综合分析岩石高边坡和地下洞室围岩的爆破振动破坏机制、动力稳定性评价方法及爆破振动对新浇混凝土影响等方面的研究现状与进展,介绍国内水电行业采用的有关岩石高边坡、地下洞室围岩、基岩以及新浇混凝土的主要爆破振动安全判据及爆破速度允许标准,并与矿山领域的相关标准进行对比。指出以往爆破振动破坏机制研究中存在的问题和现有爆破安全判据的不足,如未区分爆破地震波作用下岩体中的波传播问题和边坡动力响应问题的不同破坏机制,爆破振动安全判据未考虑振动频率和持续时间的影响。最后提出今后在爆破振动破坏机制研究,体现幅值、频率和持续时间综合影响的爆破振动安全判据确定,考虑温度应力的新浇混凝土爆破振动安全允许标准制定等方面的努力方向。     

桥梁在爆破振动作用下的振动监测方案设计

本文依托某实际工程项目即爆破振动施工对临近桥梁结构影响,详细介绍了爆破振动作用下桥梁结构安全性的爆破振动监测方案设计,通过这套监测方案设计从而达到有效进行爆破振动监测的目的。     

强夯、打桩、爆破振动对建筑物影响的探讨

强夯，打桩，爆破等施工方法引起的振动影响是一个极为敏感的问题，本文根据振动实测资料与振动特点的分析，提出结构可能产生破坏的标准，振动衰减计算公式。     

临近村庄的铁路路堤爆破方案优化

以锦阜高铁路扩能改造工程项目为背景,依据路堤初次爆破方案的参数设计和振动监测数据,分析了路堤原方案爆破效果存在的问题,针对振速过大和房屋破坏的情况,对路堤的爆破方案进行优化,并通过监测到的测点振速和爆源距,得出爆破振动速度衰减公式,保证了临近村庄结构的安全,对后续路堤爆破设计和类似路堤爆破施工有一定参考意义。     

溪洛渡电站地下洞室群爆破地震效应的研究

 采用现场爆破振动测试研究复杂地下导流洞群爆破地震波传播规律,并利用萨道夫斯基经验公式对测试数据进行回归分析,测试结果表明水平向爆破质点峰值振动速度可以作为地下洞室的安全判据;应用FLAC3D数值软件模拟爆破振动对相邻洞室的影响,得到爆破振动作用下相邻洞室振动速度、应力和位移的分布规律,并从静载作用和动载作用两方面分析评价相邻洞室的安全稳定性。计算结果表明：现场测试结果与计算结果吻合较好;采用振动速度作为安全判据是可行的;爆破振动作用下相邻洞室迎爆侧是容易出现破坏的区域,且随着冲击荷载增大,迎爆侧直墙最容易出现拉伸破坏。最后针对具体工程,根据相邻洞室洞壁最大拉应力与最大振动速度的统计关系,并结合岩石动态抗拉强度准则提出爆破振动作用下相邻洞室发生破坏的临界振动速度。     

爆破地震频率对建,建筑物破坏的影响

本文阐述了爆破地震对建，构筑物的破坏除与振动速度和爆破距离等因素有关外，还要考虑爆破地震频率这一重要因素，以期对正确评判爆破振动的安全标准起到一定的指导作用。     

龙滩水电站蠕变体边坡的爆破振动控制研究

对龙滩水电站蠕变体边坡的爆破振动进行观测、分析和处理，得到了爆破地震波衰减经验公式。根据该蠕变体边坡的特点，提出了爆破振动破坏标准。由经验公式和破坏标准，得出了蠕变体边坡新浇混凝土支护区爆破安全控制参量。最后结合该蠕变体边坡爆破实际，建议了爆破降震措施。从工程实施的效果来看，本文的研究成果与结论得到了较好的应用，保障了该工程爆破的顺利完成。     

隧道爆破振动对上方居民楼震害分析

为了保证房屋安全,对地表和居民楼进行了监测,以便及时调整爆破参数。结合房屋的破坏特点与监测数据进行了分析,研究表明:隧道爆破引起地表和房屋的振动速度和频率存在差异,随着高度变化房屋振动随之减小。对爆破振动的衰减规律和房屋的响应特征进行了总结分析,得出破坏的原因是:微差爆破时间过短,波形有重叠放大现象;自振频率和爆破频率接近,有共振现象;空洞效应放大了振速;房屋年代久远。最后提出了减振的对策,对爆破有较好的控制。     

基于小波变换的爆破振动时频特征分析

应用小波变换方法对短时非平稳爆破振动过程提出了时频特征分析。根据离散小波变换的分层分解展开关系，将爆破振动时间历史信号用分层重构信号进行扫描。应用这些信号可以给出不同频率带上爆破振动的相对能量分布和振动强度的时间变化规律。一个爆破振动实测结果的分析表明，与建立在传统Fourier变换基础上的频谱分析方法相比，基于小波变换的爆破振动时频特征分析可以给出更为准确的细节信息。文中的研究结果为爆破振动结构安全性分析提供了新的途径。     

Frequency comparison of blast-induced vibration per delay for the full-face millisecond delay blasting in underground opening excavation

Responses and damage to the structures subjected to blast-induced vibration are highly dependent on vibration frequency. Understanding the vibration frequency characteristics and its formation mechanism is essential for the safe and economic design of mining and construction blasts. When millisecond delay blasting is used in excavation, a global frequency value of all of the delays of vibrations fails to present a true picture of the vibration frequency characteristics. In the present study, comparisons of frequency characteristics for the blast-induced vibration per delay were first conducted via an underground opening case excavated by the full-face millisecond delay blasting sequence. The results show that if the blasthole geometry and charge structure are kept the same in each blast delay, the frequencies of single-delay vibration signals will decrease as the dimensions of the equivalent blasting vibration sources increase. However, the cutting blast used for the headmost holes inside is an exception, and its vibration frequency is lower than that of the breaking blast outside. It is the authors’ belief that this counter-intuitive phenomenon is caused by the free faces created by the cutting blast for the breaking blast. A small-scale blasting test and the related numerical simulation were subsequently performed to demonstrate this belief. It is found that the vibration frequency from the holes in the free-face blast is higher than that in the confined blast. In terms vibration frequency, therefore, the vibration from the breaking blast is less harmful to structures compared to the cutting blast for a certain velocity, and decreasing the burden of breaking blastholes is beneficial to reduce the vibrational damage of structures.     

Safety of engineered structures against blast vibrations:A case study

Blasting used for rock excavation is associated with ground vibrations having potential damage to surrounding structures.The extent of damage produced in a structure depends largely on ground motion characteristics,dynamic characteristics of structure and the type of geological strata on which it is founded.The safety of surrounding structures against blast vibrations is a cause of concern.However,use of a systematic approach to rock blasting helps to complete the excavation safely in time without endangering the safety of surrounding structures.Various steps are commonly adopted at construction sites to ensure safety of engineered structures against blast vibrations,e.g.adopting a suitable safe vibration level,developing site-specific attenuation relation,estimating safe charges for different distances,designing blasting pattern,and monitoring vibrations during actual blasting.The paper describes the details of studies conducted for ensuring safety of an 85 years old masonry dam and green concrete of varying ages during excavation of about 30,000 m~3 of hard rock in Maharashtra,India.The studies helped to complete the rock excavation safely in time and the safety of the dam was ensured by monitoring blast vibrations during actual rock excavation.     

Damage assessment of basaltic rock mass due to repeated blasting in a railway tunnelling project – A case study

The demand for tunnelling and underground space creation is rapidly growing due to the requirement of civil infrastructure projects and urbanisation. Blasting remains the most inexpensive method of underground excavations in hard rock. Unfortunately, there are no specific safety guidelines available for the blasted tunnels with regards to the threshold limits of vibrations caused by repeated blasting activity in the close proximity. This paper presents the results of a comprehensive study conducted to find out the effect of repeated blast loading on the damage experienced by jointed basaltic rock mass during tunnelling works. Conducting of multiple rounds of blasts for various civil excavations in a railway tunnel imparted repeated loading on rock mass of sidewall and roof of the tunnel. The blast induced damage was assessed by using vibration attenuation equations of charge weight scaling law and measured by borehole extensometers and borehole camera. Ground vibrations of each blasting round were also monitored by triaxial geophones installed near the borehole extensometers. The peak particle velocity (V_max) observations and plastic deformations from borehole extensometers were used to develop a site specific damage model. The study reveals that repeated dynamic loading imparted on the exposed tunnel from subsequent blasts, in the vicinity, resulted in rock mass damage at lesser vibration levels than the critical peak particle velocity (V_cr). It was found that, the repeated blast loading resulted in the near-field damage due to high frequency waves and far-field damage due to low frequency waves. The far field damage, after 45–50 occurrences of blast loading, was up to 55% of the near-field damage in basaltic rock mass. The findings of the study clearly indicate that the phenomena of repeated blasting with respect to number of cycles of loading should be taken into consideration for proper assessment of blast induced damage in underground excavations.     

Determination of blast-induced ground vibration equations for rocks using mechanical and geological properties

In the recent decades,effects of blast loads on natural and man-made structures have gained considerable attention due to increase in threat from various man-made activities.Site-specific empirical relationships for calculation of blast-induced vibration parameters like peak particle velocity(PPV) and peak particle displacement(PPD) are commonly used for estimation of blast loads in design.However,these relationships are not able to consider the variation in rock parameters and uncertainty of in situ conditions.In this paper,a total of 1089 published blast data of various researchers in different rock sites have been collected and used to propose generalized empirical model for PPV by considering the effects of rock parameters like unit weight,rock quality designation(RQD),geological strength index(GSI),and uniaxial compressive strength(UCS).The proposed PPV model has a good correlation coefficient and hence it can be directly used in prediction of blast-induced vibrations in rocks.Standard errors and coefficient of correlations of the predicted blast-induced vibration parameters are obtained with respect to the observed field data.The proposed empirical model for PPV has also been compared with the empirical models available for blast vibrations predictions given by other researchers and found to be in good agreement with specific cases.     

交通系统环境振动评价问题的探讨

通过对武汉市轻轨一号线一期工程环境振动的现场测试,研究轻轨对周边地面和邻近建筑物的振动影响。实测结果表明:高架轨道交通所引起的环境振动随着距轨道中心线距离增加而减小,但在建筑物地基附近存在振动放大现象;本底振动对总体振动的影响随着距轨道中心线距离增加也逐渐增大;对于多层建筑物,楼层越高,振动越强烈。     

工程爆破安全振动速度综合研究

对爆破振动效应研究成果和国内外常用的安全振动速度准则进行了综合比较，结合重庆市地铁钻爆法施工爆破振动效应研究，提出了关于爆破振动安全速度规定的分类建议值。     

城市浅埋隧道爆破地震波的降振技术

结合工程实践,本文介绍了厦门机场路一期工程（仙岳路-演武大桥段）JC3合同段隧道爆破降震试验与爆破振动监测。根据监测数据分析发现,爆破振动的最大值不是出现在最大段药量爆破的时刻而是出现在掏槽孔,并根据监测结果修改爆破设计,最终使地表爆破震动振速控制在0.5cm／s以内,确保了地表建筑群的安全与隧道施工的正常进行,其成功经验可为今后同类工程提供借鉴。     

轨道交通引起的环境振动及其影响规律

从轨道交通引起的环境振动对人体、建筑物、精密仪器三个方面的影响进行了总结：对振动加速度随振源埋深的变化、距离轨道中心线的分布规律以及列车车速和载重对其的影响规律做了重点分析。文中相关结论可以为解决城市环境灾害以及城市轨道交通建设工程提供参考依据。     

爆炸冲击振动对人体健康影响的评价

讨论了爆炸冲击振动对人体健康影响的评价方法,阐述了振动剂量法提出的依据和影响因素,并用振动剂量法统一了爆炸冲击和振动下人体耐受限的取值方法,提出了取VDV=25m·S-1.75作为爆炸冲击振动下保证人员安全的容许振动剂量值.     

Damage to surface structures due to blast vibration

This paper describes effect of blast produced ground vibration on damage potential to residential structures to determine safe levels of ground vibration for the residential structures and other buildings in mining areas. Impacts of 341 blasts detonated at two mines were monitored at the test structures and 1871 blast vibrations signatures were recorded on or near the test structures. Cosmetic cracks in a native brick-mud-cement house were detected at peak particle velocities (PPV) between 51.6 and 56.3 mm/s. The reinforced concrete and cement mortar (RCC) structure experienced cosmetic cracks at PPVs of 68.6–71.3 mm/s at the first floor, whereas at second floor it was detected at PPV levels of 71.2–72.2 mm/s. Minor damage in brick-mud-cement house was recorded at PPV levels of 81.0–89.7 mm/s. The RCC structure at first and second floors experienced minor damage at PPV levels of 104 and 98.3–118 mm/s, respectively. The brick-mud-cement house experienced major damage at PPV level of 99.6–113.0 mm/s, while major damage was recorded in RCC structure on first floor at PPV of 122 mm/s, the second floor at PPV levels of 128.9–161 mm/s. Recommended threshold limits of vibrations for the different type of structures is based on these measurements and observations.