Smooth blasting design and optimization of large spanurban highway tunnels

Vibration resistance can be incorporated into blasting designs to avoid damages caused by the excavation of large span tunnels in busy urban areas, but only by basing excavation design schemes on actual situations. In view of the actual situation in the Jahua tunnel in Chongqing, P. R. China, research was conducted to identify a relevant explosion scheme. The research was based on theoretical analysis and in situ testing. Face step excavation was considered in the broadening band A, and upper drift excavation was adopted in broadening bands B, C, D and E. We simultaneously proposed selection criteria for smooth blasting parameters and the construction layout of broadening band B. Based on a regression analysis of the blasting vibration monitoring results, a spread orderliness of blasting vibration was drawn. Explosion parameters optimization measures were put forward, selected from the maximum charge quantity, millisecond blasting, reasonable blasting time difference, and the excavation plan. Field testing achieved satisfactory results. These findings will play an important role in guiding excavation blasting construction of tunnel projects and assuring the safety of ground buildings.     

Finite Element Analysis on Interaction of Neighboring Highway Tunnels under Construction

Recently, the construction of neighboring highway tunnels with small interval gets more and more in China. The construction of such tunnels proceeds usually by excavating one after another. The second tunnel is constructed with the surrounding rock disturbed by the first one. And the construction of second tunnel also has effect on the first excavated one. For revealing the interaction laws of such tunnel construction in combination with the engineering practice of Lanfeng tunnel at Jinshan Road in Chongqing, The FE numerical simulation analysis was used to study the characters of surrounding rock deformation, stress field, and plastic zone of the tunnel. From this analysis, it clearly shows that the excavation of second tunnel has significant influence on the first one. This study provides a scientific basis for design and excavation of neighboring highway tunnels.     

Building Damage in Mianyang City Caused by the May 12, 2008 Earthquake in Wenchuan, Sichuan Province, P. R. China

Summarizing building damage in all previous large earthquakes is an important approach to promote the development of structural seismic design. We conducted a statistical analysis of the earthquake damage to various buildings in Mianyang city, Sichuan province, P. R. China. This analysis was based on the emergency assessment and investigation of building damage in Mianyang city caused by the large earthquake that occurred on May 12, 2008 in Wenchuan. We also summarize the damage characteristics of different buildings and the lessons learned. We present the following findings and suggestions for structural seismic design:(1)Buildings in Mianyang designed according to current seismic code withstood the rare earthquake.(2)Different structural systems have obviously varied seismic behaviors. (3)Old buildings always have been the weak links in earthquakes, and should be evaluated and strengthened selectively after an earthquake.(4)Studies of anti cracking measures for masonry walls should be conducted. (5)Effective measures should be taken to reduce earthquake damage to non structural components, for example, infill walls in frames.(6)Seismic design methods and construction measures for stairs should be studied.     

雷暴天气下建筑物周围电场畸变区域的研究分析

为了探究在雷暴发生时建筑物周围电场畸变区域的规律,利用Integrated Engineering Software电磁暂态仿真软件,模拟分析雷暴云及建筑物结构对周围电场畸变特征的影响。结果表明：当雷暴云过境时,群体建筑物遭受雷击的概率会减小,这主要是因为群体建筑物之间的屏蔽效应,改变了周围区域的电场畸变程度,降低了产生上行先导的概率和遭受雷击的概率。对于单体建筑而言,当雷暴云过境时,建筑物周围电场畸变区域呈半球形状,电场的畸变程度与建筑物的高度呈线性相关,高度越高,畸变区域越大,将导致前方流注扩展的区域变大,从而增加了下行先导发生的概率,这也是越高的物体易遭受雷击的原因。     

Analysis of Solid Fluid Coupling for Tunnel Excavation in Complicated Fractured Rock Masses

When tunnels are through water bearing section of fractured rock mass, a complex interaction process between rock mass deformation and fluid transportation is one of the most important reasons for water gushing, water bursting and mud bursting.To study the rock mass deformation and fluid transportation in tunnel excavation under complex geological conditions, a hydraulic model of complex crack rock mass was established from the relationship between the crack growth degree of surrounding rock in deep buried tunnel and the engineering scale, with which fracture network of different levels in rock mass could be considered simultaneously.Furthermore,a computer Fortran program was put forward to simulate the solid fluid coupling of excavation process of a deep buried tunnel.And it was found that the principal fractures had strong flowing action and network fractures had storage function and lag effect in seepage area.And the yield area of surrounding rock was increased under the coupling of seepage field and stress field.     

Analysis on the Stress of the Tunnel Underground High Buildings

With the problem of the city development, it becomes very important and urgent to research the utilization of the urban underground space. The authors discuss the interaction of high buildings and tunnel which belongs to a project at Dadukou region in Chongqing. The authors simulate this condition in computer and analyses the stress around the tunnel and find the rang of stress concentration. At last,the authors offer some references for underground-space opening of the tunnel under high buildings.     

Calculation of Influence on Longitudinal Deformation of Adjacent Tunnels Due to Excavation

Unloading of excavation of foundation pit has influence on adjacent tunnels, therefore it is important to predict the deformation of metro tunnels to ensure the operation of tunnel. The displacement effect due to the surrounding wall soil unloading of adjacent excavation was not considered by the theoretical analysis method, and the analysis procedure of FEM was usually too complicated to get a satisfied result, so the horizontal and vertical additional stress were calculated by the Mindlin solutions. Furthermore, the tunnel structure was considered as the beam with infinite length. The additional stress was imposed on the Winkler model and the governing equation was built up on the adjacent tunnel structure. Finally, displacements and internal forces of existing tunnels were obtained. Compared with the numerical simulation and an engineering case, the results of the presented formula are in good agreement. It can provide certain theoretical and calculation basis for metro tunnels influenced by adjacent excavation.     

Earthquake Response Properties of the Support Structure of Large Cross Section Tunnel

The response properties of displacement and stress of tunnel support structure are discussed in detail under the action of horizontal earthquake acceleration(Ya),longitudinal earthquake acceleration(Za) and horizontal-longitudinal earthquake acceleration(YZa).This discussion is based on an analysis of the surrounding rock-support structure-earthquake interaction,adoption of an ADINA nonlinear finite element and construction mechanics,and transient dynamic time domain analysis of a large cross section tunnel.Results of analysis show that:(1) Horizontal earthquake acceleration has important influence on horizontal displacement,maximum principal stress,acceleration and velocity.(2) Longitudinal earthquake acceleration has important influence on longitudinal displacement,effective stress,maximum and minimum principal stress,maximum shear stress,acceleration and velocity.(3) When Ya=0.191g and 0.440g or Za=0.141g and their combined action,the initial support of tunnel would be damaged and the local lining would have partial damage.(4) When Ya=0.440g or Za=0.326g and their combined action,the lining of tunnel would be damaged.(5) When Ya=0.880g or l Za=0.652g,the support structure of tunnel would have severe damage.     

Research on the Body Coefficient of Complicated Tall Buildings

Considering the complication of the coefficient of wind-induced vibration for tall buildings,the scale 1:300 model test of Ying Li Building is completed in the second wind tunnel of Beijing University.Based on the calculation and analysis of the test results,the static and dynamic wind pressure acting on the building can be obtained and the value of the coefficient of wind-induced vibration for this tall building can be solved directly,thus a new way is laid for the research of complicated tall buildings.     

实测确定公路隧道洞外景物亮度的方法

分析比较了查表法、环境简图法和黑度法3种确定洞外亮度的方法,发现3种方法均未完全考虑隧道所处区域的环境和光气候条件。为了能快速准确地确定隧道洞外景物亮度,以从莞高速公路的7座隧道为测量对象,通过现场实测,建立了洞外景物亮度与水平面照度之间的关系。在对当地光气候数据进行统计分析的基础上,确定隧道洞外景物亮度标准值、东莞地区隧道洞外典型景物亮度设计参考值,并得到了东莞地区4个朝向隧道洞外典型景物亮度值。     

Relationship of Conservation of Historic Buildings and Urban Construction

The conservation of historic buildings and their environment is an unavoidable problem in urban construction. In this paper, the authors give a few new thoughts about the problem. First, the historic buildings are important part of the core power in city competition.Second,the conservation work should be combined with their development. Third, a classified and multilevel system of protection and reuse of old buildings should be set up.     

植物性杀虫剂辣根素对天牛的防治研究

为明确辣根素对天牛的熏蒸致死作用,在田间研究了辣根素不同剂量对天牛幼虫的熏蒸作用、对天牛熏蒸的致死时间、天牛蛀道以及封口的处理方式。结果表明,利用辣根素熏蒸防治天牛,将蛀道口处清理干净,以0.5~1.0 mL/孔的使用剂量进行处理,蛀道口及排粪孔用高岭土饱和盐水泥进行封闭,外用地膜包扎,在处理1天后对天牛可以达到96.7%以上的防治效果。辣根素是一种非常有效的防治天牛的植物性杀虫剂。     

节理岩体中连拱隧道施工对周边建筑物的影响

以重庆东水门大桥—千厮门大桥渝中区连接隧道为研究对象,基于UDEC软件建立离散元数值模拟分析模型,研究了城区连拱隧道施工引起的地表沉降,上部建筑物基础沉降及倾斜,新建隧道下方已有轨道六号线的变形、受力特征,并将监测数据与数值模拟进行对比分析。结果表明,连拱隧道左侧隧道上导坑施工引起的隧道拱顶沉降和基础沉降量最大,经计算上部建筑物基础最大沉降量为3.81 mm,最大倾斜量为0.02%,建筑物基础沉降量和倾斜在规范许可范围之内;隧道施工引起的地层损失使得轨道六号线左拱肩向上隆起,六号线弯矩分布规律和其变形形态基本一致,弯矩最大值位于左拱肩部位,最大值为238 kN·m;数值模拟计算结果与监测数据量值相当,变形趋势基本一致;采用UDEC软件可以准确地计算出隧道开挖过程中节理的存在对隧道周围建筑物变形的影响。     

Model of Critical Velocity for Fire Ventilation in Horizontal Tunnels

1/20 scale model test and full scale field test were carried out to study the critical velocity for fire ventilation in horizontal tunnels. Combined with the test results, small scale test results by Jae and full scale test and simulation by Hu, a semi empirical model was developed to predict the longitudinal critical velocity for tunnel fire ventilation. Compared with the predictions of the proposed model and other models using air as fire source, it was found that the predictions by Wu and Barker was underestimates.     

转Bt基因玉米对亚洲玉米螟的抗性评价

转Bt基因抗虫玉米为诺华公司含Bt11转化系的杂交种NX4777,能全株表达Cry1Ab杀虫蛋白,以其非转基因受体玉米品种NX4906为对照。在玉米生长至心叶中期(50~60cm高)、抽雄前期和抽丝散粉期分别进行人工接亚洲玉米螟[Ostrinia furnacalis (Guenée)]初孵幼虫40~60头。以食叶级别、存活幼虫数、蛀孔数、隧道长度和雌穗被害级别等,分别作为评价玉米心叶期和穗期的抗性标准。结果表明,Bt玉米食叶级别仅为1级,显著低于对照的7级。Bt玉米平均每株存活幼虫0.04~0.20头、蛀孔0.11~0.15个、隧道长度0.13~0.41cm,雌穗被害级别为0,植株折茎率为0,而对照玉米平均每株存活幼虫6.19~12.41头、蛀孔4.48~7.05个、隧道长度12.41~24.09cm,雌穗被害级别为5.9,植株折茎率高达73.6%~95.5%。室内生测结果亦表明,取食Bt玉米心叶、雄穗的初孵幼虫3d全部死亡,取食花丝7d死亡率达到99%,相比之下取食常规玉米的存活率在88.7%以上。表明表达Cry1Ab杀虫蛋白的Bt对亚洲玉米螟具有很高的抗虫性,能够保护玉米全生育期免受玉米螟的危害。     

考虑驾驶员视觉适应的公路隧道入口段亮度确定方法

驾驶员的视觉适应过程直接影响交通安全。为考虑驾驶员的视觉适应过程,在确定公路隧道入口段亮度时,通过实测得到驾驶员驾车进入隧道过程中的瞳孔大小变化数据,建立了描述驾驶员驾车进入隧道过程中瞳孔面积变化速率最大值与各相关参数之间关系的数学模型。以驾驶员不发生视觉障碍的瞳孔面积变化临界速率为基准,计算得到了驾驶员瞳孔面积变化达到临界速率时,隧道入口段的最低亮度,分析了隧道入口段所需最低亮度与洞外亮度之间的关系,通过回归分析建立了隧道入口段亮度与洞外亮度之间关系的数学模型,得到了考虑驾驶员视觉适应的公路隧道入口段亮度确定方法。     

Study of Tunnel Supporting Effect

Based on the elastic theory, an analysis can be made on stress and plastic deformation under tunnel excavation and shotcrete support.FLAC 3D can be used to simulate the mechanical behavior of excavation and support, getting the deformation of surrounding rock stress and plastic without support and shotcrete. The results show that, the prestress applied on the anchor equals to the supporting force when the tunnel plastic zone disappears. This support improves the self bearing capacity of surrounding rock, effectively suppresses the expansion of the plastic zone after the tunnel excavation, and prevents further damage to the tunnel surrounding rock.     

Influence of blasting vibration on adjacent buildings of station tunnel

The influence of blasting vibration on the adjacent buildings is inevitable if blasting is employed for excavation. Daping station tunnel of Chongqing light railway project, on which there is dense with population and buildings, has a minimum buried depth of only four meters and maximum span length of 26.3 meters. The stepped excavation mode with short hole, multi round and V shaped cut are adopted. The maximum charge weight of one delayed interval is determined by the permitted vibration velocity. The smooth blasting technology with adding vibration reduction holes is used. Meanwhile, the charge weight per hole is strictly controlled. With the simulation and on site test, it is found that the proposed technology for tunnel construction is feasible.     

Effectiveness of Energy use in Public Area of Buildings

The flow of people changes very greatly in the public areas of public buildings, so the energy demand should also change with the flow of people. However, under the traditional model, the pedestrian flow is rarely considered when accounting energy output, which causes some of the energy invalid. How to assess the energy efficiency to reduce energy waste is an emergent problem to be solved for building energy conservation. The concept of energy utilization efficiency is put forward to judge the degree of utilization of energy, and the formula for calculating energy utilization efficiency is also provided. In a hospital public waiting area, a lot of experiments have been carried out. By comparing the energy consumption before and after the experiments, it is found that energy utilization efficiency can assess the effectiveness of energy. And to improve the energy efficiency of buildings greatly in public areas can be realized by promoting the energy utilization efficiency.