Preliminary analysis of the hanging wall effect and velocity pulse of the 5.12 Wenchuan earthquake

A preliminary study of the PGA attenuation, hanging wall effect and velocity pulse characteristics from the 2008 Wenchuan earthquake ofMS -8.0 is described in this paper. The study was carried out through analyses in the time and frequency domains of main earthquake records. In the PGA attenuation study, records from 316 stations less than 1000 km from the surface rupture of the fault were used as a database and attenuation relationships were developed and compared with some existing relationships that are widely used in China's Mainland, Chinese Taiwan and the US. At the same time, records from 28 stations less than 100 km from the fault were used to study the hanging wall effect and velocity pulse characteristics of this earthquake based on the distribution of PGA, PGV, spectral acceleration, and the velocity pulse peak, and the results are compared with the 1999 Chi-Chi earthquake. In addition, the large PGAs of the UD components observed in this event are also discussed in this paper. From the results of the preliminary study, some conclusions are developed and suggestions for further research are proposed.

Rupture directivity and hanging wall effect in near field strong ground motion simulation

A random synthesis procedure based on finite fault model is adopted for near field strong ground motion simulation in this paper. The fault plane of the source is divided into a number of sub-sources, the whole moment magnitude is also divided into more sub-events. The Fourier spectrum of ground motion caused by a sub-event in given sub-source, then can be derived by means of taking the point source spectrum, attenuation with distance, energy dissipation, and near surface effect, into account. A time history is synthesized from this amplitude spectrum and a random phase spectrum, and being combined with an envelope function. The ground motion is worked out by superposition of all time histories from each sub-event in each sub-source, with time lags determining by the differences between the triggering times of sub-events and distances of the sub-sources. From the example of simulations at 21 near field points in a scenario earthquake with 4 dip angles of the fault plane, it is illustrated that the procedure can describe the rupture directivity and hanging wall effect very well. To validate the procedure, the response spectra and time histories recorded at three near fault stations MCN, LV3 and PCD during the Northridge earthquake in 1994, are compared with the simulated ones.

A new attenuation model of near-fault ground motions with consideration of the hanging wall effect in the Wenchuan earthquake

The hanging wall effect is an important factor that impacts the characteristics of strong ground motions in near-fault areas. Based on a residual analysis of ground motion parameters characterizing the hanging wall effect and in recognition of the nature of the effect, many models have been developed. In this study, after a comprehensive analysis of two existing models, a new model is proposed and used to model the hanging wall effect in horizontal peak ground acceleration （PGAH） and spectral acceleration （SAH） at a period of 0.1s in the Wenchuan earthquake. Finally, comparisons between the modeling results of the hanging wall effect in the Wenchuan earthquake and the results predicted by using Abrahamson and Silva＇s NGA model （AS NGA） indicate that the AS NGA model predicts a much higher hanging wall effect than the model developed in this paper. Furthermore, the AS NGA model predicts a large hanging wall effect even at great distances, while the proposed model more accurately captures the trend of the effect.

Effects of hanging wall and footwall on demand of structural input energy during the 2008 Wenchuan earthquake

Systematic differences in the duration and frequency content of ground motions from the hanging wall and footwall during the 2008 Wenchuan earthquake are investigated,focusing on the influence of these differences on structural input energy based on the elastic and inelastic energy responses of structures.A comparison of the input energy spectra between the hanging wall and the footwall reveal that the structural input energy on the hanging wall is not amplified due to the short duration and low peak ground velocity to acceleration ratio（V/A）.However,the larger demand of structural input energy on the footwall in the range of medium and long periods is observed and the demand increases up to 50% relative to the average level of structural input energy for rupture distances larger than 30 km.The importance of considering the footwall effect on structural input energy when comparing ground motions in the range of medium and long periods is recognized.

Influence of Stope Design on Stability of Hanging Wall Decline in Cibaliung Underground Gold Mine

Cibaliung Underground Gold Mine applies cut and fill mining method to optimize ore production and maintain underground stability. Existing 5 m × 5 m height and width of stope geometry has a potential new design to increase production of gold due to variety of thick ore, however serious shotcrete failures often occur in hanging wall decline. This paper aims to find out the relationship between stope design and stability of hanging wall decline. The analysis conducted in this study is based on underground characteristics and geological condition of Cibaliung area. The impact of stope design on decline stability was analyzed by using numerical methods. The impact factors such as different rock mass, size of stope, and distance between stope and hanging wall decline were used in the analysis of underground stability especially stability on hanging wall decline.

Effects of the hanging wall and footwall on peak acceleration during the Jiji (Chi-Chi), Taiwan Province, earthquake

The M=7.6 Jiji (Chi-Chi) earthquake, Taiwan Province, on September 21, 1999 (local time) is a thrust fault style earthquake. The empirical attenuation relations of the horizontal and vertical peak ground accelerations (PGA) for the Jiji (Chi-Chi) earthquake are developed by regression method. By examining the residuals from the Jiji (Chi-Chi) earthquake-specific peak acceleration attenuation relations, it is found that there are systematic differences between PGA on the hanging-wall and footwall. The recorded peak accelerations are higher on the hanging-wall and lower on the footwall. The clear asymmetry of PGA distribution to the surface rupture trace can also be seen from the PGA contour map. These evidences indicate that the PGA attenuates faster on the hanging-wall than on the footwall. In the study of near-source strong motion, seismic hazard assessment, scenario earthquake and seismic disaster prediction, the style-of-faulting must be considered in order that the attenuation model can reflect the characteristic of ground motion in various seismic environmental regions.

Effects of hanging wall and forward directivity in the 1999 Chi-Chi earthquake on inelastic displacement response of structures

The characteristics of the inelastic response of structures affected by hanging wall and forward directivity in the 1999 Chi-Chi earthquake are investigated. Inelastic displacement ratios （IDRs） for ground motions impacted by these nearfield effects are evaluated and comprehensively compared to far-field ground motions. In addition, the inelastic displacement responses to hanging wall and footwall ground motions are compared. It is concluded that the inelastic displacement response is significantly affected in the short period range by hanging wall and in the long period range by footwall. Although high peak ground acceleration was observed at hanging wall stations, the IDRs for structures on hanging wall sites are only larger than footwall sites in the very long period range. Forward directivity effects result in larger IDRs for periods longer than about 0.5s. Adopting statistical relationships for IDRs established using far-field ground motions may lead to either overestimation or underestimation in the seismic evaluation of existing structures located in near-field regions, depending on their fundamental vibration periods.

Geometric effects resulting from the asymmetry of dipping fault:Hanging wall/ footwall effects

Root-mean-square distance Drms with characteristic of weighted-average is introduced in this article firstly. Drms can be used to capture the general proximity of a site to a dipping fault plane comparing with the rupture distance Drup and the seismogenic distance Dseis. Then, using Drup, Dseis and Drms, the hanging wall/footwall effects on the peak ground acceleration (PGA) during the 1999 Chi-Chi earthquake are evaluated by regression analysis. The logarithm residual shows that the PGA on hanging wall is much greater than that on footwall at the same Drup or Dseis when the Drup or Dseis is used as site-to-source distance measure. In contrast, there is no significant difference between the PGA on hanging wall and that on footwall at the same Drms when Drms is used. This result confirms that the hanging wall/footwall effect is mainly a geometric effect caused by the asymmetry of dipping fault. Therefore, the hanging wall/footwall effect on the near-fault ground motions can be ignored in the future attenuation analysis if the root-mean-square distance Drms is used as the site-to-source distance measure.

Xinji Wall Hanging,a Flower of Chinese Folk Art

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逆断层上下盘开采扰动下断层活化响应模拟研究

为探究煤层不同开采方式下逆断层应力场、位移场演化规律和断层活化规律,通过数值模拟分析逆断层地质条件下进行上盘开采和下盘开采时断层处的正应力和剪应力演化规律、断层活化过程以及断层和覆岩的位移场变化特征。研究结果表明:随工作面逐渐靠近断层,断层上部的正应力逐渐降低、剪应力逐渐升高,断层下方的正应力逐渐升高、剪应力逐渐降低,正应力和剪应力升高或降低的速率随工作面与断层距离减小而增加;当工作面与断层距离在80 m和40 m时,断层处正应力和剪应力发生异于前期应力规律性的变化,出现大幅度增长和降低的情况;相对于上盘开采,下盘开采时断层更易受煤层开采扰动而发生活化,且活化程度和范围均大于上盘开采;随工作面不断向断层靠近,下盘开采时采空区上覆岩层下沉量和断层两侧岩体相对位移量均明显大于上盘开采。研究结果对煤层开采遇断层时围岩治理和防灾减灾具有一定科学指导意义。

露天地下楔形转接过渡诱导冒落控制边坡岩移危害技术研究

露天地下楔形转接过渡模式的安全管控是利用崩落法开采挂帮矿形成的塌陷坑阻止边坡岩移威胁露天采场,但地采扰动下的高陡边坡破坏过程不易控制,因而制约了楔形转接过渡模式在大型深凹露天矿山中的应用。针对上述问题,结合极限平衡分析方法,揭示出崩落法开采扰动下的高陡边坡渐进破坏规律,提出了边坡滑移体体积计算方法,以及通过调控回采顺序控制边坡滑移进程以实现塌陷坑完全承接边坡滑移体的边坡岩移危害控制技术。研究表明:边坡岩体不会随挂帮矿向下开采而发生持续破坏,只有当挂帮矿开采至关键分段时,边坡岩体受力状态超过极限平衡状态才发生滑移破坏,可通过滞后回采关键分段上盘三角矿延缓边坡滑移,以及通过滞后回采关键分段下盘矿体和采用下向阶梯状回采工作面增大塌陷坑容积,最终实现塌陷坑有序承接边坡滑移体。研究成果完善了大型深凹露天矿楔形转接过渡的安全管控方法,提高了楔形转接过渡模式的适用性。

深凹露天矿山挂帮矿安全回采工艺研究及实践

为充分回收挂帮矿资源,根据攀西某深凹露天矿山挂帮矿赋存条件及内排土堆排情况,本文提出“内排土连续回填、挂帮矿分步回采”工艺。利用内排土修筑临时道路至回采平台,为回采工作创造设备运转空间;同时连续回填采坑,缩短挂帮矿回采完成后边坡暴露时间。采用靠帮预裂爆破,控制单响起爆药量在250 kg以下,使用等效载荷加载于回采区域,经计算,边坡最大振动速度1.6 cm/s,满足边坡安全速度要求。建立边坡三维模型,计算了回采工艺全过程中边坡位移变化情况,回采完成后边坡整体位移均小于0.5 cm,不会出现大范围边坡失稳。经现场实际应用,累计采出矿石超过58.34万t,且边坡稳定。为矿山下一步全面回采挂帮矿资源提供技术支撑,可供类似矿山参考借鉴。

基于Simulation的薄壁桶搬运过程的形变研究

桶料的搬运方式主要有托底式、夹取式和挂取(吊取)式,文中针对薄壁桶的搬运方式进行模拟分析,通过模拟分析的具体数值来进行合理的选择。主要对挂取(吊取)和夹取2种薄壁桶的搬运方式进行模拟分析,基于Soildworks中的Simulation进行计算,并得出具体数值,选取合理的薄壁桶搬运方式。模拟分析表明:在同等桶壁厚的情况下,夹取式桶料搬运形式薄壁桶的变形程度较大,主要体现在薄壁桶的夹持部位,如特定场景需夹持薄壁桶的桶身进行搬运时,还需适当加厚薄壁桶的桶壁来抵抗夹持板的夹持力,使薄壁桶不会产生较大的形变量。

港口工程吹填区悬挂式防渗墙施工技术

为探究港口工程吹填区悬挂式防渗墙施工技术,以沙特某港口工程为工程背景。首先对悬挂式防渗墙进行了设计,并综合考虑防渗墙混凝土材料以及渗流稳定情况,对悬挂式防渗墙设计进行优化。其次对悬挂式防渗墙关键施工技术进行了详细研究和论述,结合该港口工程主要施工步骤,对施工重难点进行了分析,并提出了有针对性的控制措施。

露天转地下挂帮矿崩落法开采边坡安全防控技术研究

露天转地下过渡期崩落法开采挂帮矿,会引起边坡的岩移和陷落,威胁露天矿的安全生产。以大孤山铁矿为工程背景,分析边坡岩移机理,得出挂帮矿持续冒落跨度为临界冒落跨度的1.25~1.65倍,第一分段进路布置在矿体厚度大于3.3l的位置,能够保证露天开采的安全。研究陷落散体所需的回采体积,得出回采体积先随着保安矿柱宽度的增加而减小,后又随着保安矿柱宽度的增加而增大,当保安矿柱的宽度为88.45 m时,所需回采体积最小。采用散体滑落试验,得出了防护坝设置在露天坑底的上一个台阶,保证了露天开采的安全。研究成果能够实现大孤山铁矿露天转地下过渡期的产能衔接和安全生产,对于矿山的未来发展具有重要意义。

临淄区农村燃气壁挂炉采暖住宅耗气量分析及改造

研究淄博市临淄区农村壁挂炉采暖室温与能耗的关系。在采暖季,通过典型用户实测,探讨室内温度、通风时间及围护结构参数对农村壁挂炉采暖住宅耗气量的影响,利用DeST软件分析天然气采暖的能耗状况,针对当地农宅实际情况设计围护结构的改造方案并进行模拟分析。研究表明,节能改造后的农宅在采暖季的能耗下降53%~61%。

超高大曲面玻璃砖幕墙施工技术

北京市某工程采用超高大曲面玻璃砖幕墙进行装饰,为解决传统施工工艺存在的问题,对超高大曲面玻璃砖幕墙施工关键技术进行研究,提出玻璃砖内吊挂法。采用玻璃砖内吊挂法施工时,可将传统玻璃砖幕墙施工时的受力体系进行转换,通过不锈钢通丝吊杆承受单元体玻璃砖全部重力荷载,利用转接件将各单元体进行连接,采用玻璃胶填充玻璃砖层间缝隙,以保证幕墙具有良好的整体性、稳定性、安全性和观感。

骑墙式吊篮、多点位固定支架在建筑施工中的应用

某项目总高92.65 m为了能在这种高度下进行施工,本项目采用了骑墙式吊篮和多点位固定支架的施工方式。骑墙式吊篮是一种专门针对高空作业设计的吊篮,其可在墙壁和屋面之间进行自由移动,并具有极高的灵活性和安全性。多点位固定支架则是将吊篮固定在多个位置,使吊篮在施工过程中能够保持稳定,防止因晃动而引发的安全事故。通过采用骑墙式吊篮和多点位固定支架,为幕墙安装作业提供了必要条件。同时,这种吊篮的安装方式安全可靠,大幅降低了施工过程中的安全风险。骑墙式吊篮和多点位固定支架的使用并没有占用屋面的空间,这为今后的施工提供了更多的可能性。

办公建筑干挂光伏幕墙构造优化

综合我国不同气候区和太阳能资源区,遴选5座典型城市,运用EnergyPus能耗模拟软件对办公建筑通风式和封闭式两种空腔的光伏幕墙进行能耗仿真。以全年净能耗为目标,优化光伏幕墙朝向和空腔厚度,并采用夏季、冬季高峰周空腔温度对仿真结果进行补充验证。结果表明,通风式光伏幕墙有利于降低建筑夏季冷负荷,封闭式光伏幕墙有利于降低冬季热负荷;夏热冬暖地区通风光伏幕墙空腔厚度越小,节能效果越好;其他地区最佳空腔厚度为30~50mm;封闭式光伏幕墙随空腔厚度增大,节能效果降低。严寒、寒冷、夏热冬暖地区光伏幕墙宜设置在南向,其他地区最佳朝向为西向。

双层车辆荷载作用下地下空间半悬挂车道动力响应仿真分析

[目的]新型地下综合体预应力吊墙半悬挂式行车道结构具有美观、净空大的优点,但对该新型结构的力学性能的研究尚处于起始阶段,需要对该半悬挂式车道板结构的动力特性进行深入研究。[方法]以深圳市黄木岗地下综合交通枢纽某区间半悬挂式车道板隧道为背景,采用Midas/GTS软件建立地下综合体半悬挂车道板三维有限元模型,研究了双层车辆荷载作用下半悬挂车道板的位移、加速度、应力的动态响应规律。[结果及结论]车辆动荷载作用下,车道板中部位移及加速度响应最大,沿车道板中部至侧墙连接处位移与加速度响应逐渐减弱,车道板位移响应峰值约为吊墙、顶板与侧墙的4.6~12.3倍,吊墙、顶板与侧墙的加速度响应峰值约为车道板中部的4.0%~21.6%;动荷载作用下,车道板中部以及与侧墙的连接部位应力响应明显,在车道板与侧墙的连接处出现了应力集中现象,并表现为轻微的不对称变形特征;上层车辆荷载对吊墙的位移与加速度响应幅值影响相对较大,增长幅度明显高于其他区域。