Development of the nano-composite cement:Application in regulating grouting in complex ground conditions

Improvement of the fluidity and setting time of grouting materials has been recognized as an effective approach of seepage prevention in foundation works, and it is quite common to be used for handling severe leakages in complex ground conditions, such as loose, broken and fully fissured stratum. For the purposed of better meeting the engineering requirements, experimental studies were conducted in this study with focus on the nanocomposite grouting materials and the related controlled grouting technology. As compared with the commonly used silicate-sulpho-aluminate composite cement, which is characterized by relatively poor rheological property, quick setting time and low strength, the most suitable nano-material with proper reactants were selected intentionally to improve the mentioned attributes of composite cement. Due to the setting time and strength of the targeted cement slurry behaving with poor performance of harmonization to engineering construction problems, hydration synergistic effect of these composites were investigated in our experiments. Results showed that the properties of grouting materials, including initial fluidity, setting time, ideal right-angle thickening, and early strength and late strength were sufficient to produce an expected grouting application. It is therefore advocated that the refined grouting material could provide a better solution to fix grouting problems in complex ground cementing operations.

Numerical Study on Effect of Longwall Mining on Stability of Main Roadway under Weak Ground Conditions in Indonesia

The purpose of this research is to study the effect of longwall mining on the stability of main roadway in the underground coal mine. The PT GDM （Gerbang Daya Mandiri） underground coal mine in Indonesia, where the rocks are weak, was selected as a representative study site. To accomplish the objective of the research, the finite difference code software FLAC3D was used as a tool for the numerical simulations. The longwall mining of several panel and barrier pillar widths at various depths was simulated and discussed. Based on the simulation results, it indicates that the effect of coal panel extraction on the main roadway stability depends on the width of panel and barrier pillar. The greatest effect occurs when the large panel width and the small barrier pillar width are applied, whereas the smallest effect happens when the narrow panel width and the large barrier pillar width are adopted. In this paper, therefore, to maintain the stability of the main roadway with the aim of maximizing the coal recovery, the appropriate size of panel and barrier pillar width is proposed for each mining depth for this underground coal mine.

Application of decision tree to selection of MTBM for adverse geological conditions

So many potential risks can be identifed for application of trenchless technology especially using microtunneling methods.Unexpected changes in ground conditions,such as encountering boulders,tree roots,ground water and man-made structures such as old foundations are the principal geotechnical risks,which affect the selection of an appropriate microtunnel boring machine.On the other hand,the performance of each microtunneling technique will differ while encountering such conditions.Hence,predicting the potential hazards provides a better safety and risk management plan.In this study,a couple of potentially hazardous situation,which are commonly associated with ground conditions,were identifed and investigated.A decision tree aid methodology was proposed based on geotechnical risk assessment for selection of proper microtunneling technique.Based on the approach the most appropriate microtunneling technique has the minimum risk level either before or after hazards mitigation measures.In order to check the effciency of the approach in practice,selection of microtunnel boring machine for Hamadan sewerage pipeline project was evaluated.Accordingly,an earth pressure balance(EPB)MTBM was selected for the project.

Influence of ground effect on flow field structure and aerodynamic noise of high-speed trains

The simulation of the ground effect has always been a technical difficulty in wind tunnel tests of high-speed trains.In this paper,large eddy simulation and the curl acoustic integral equation were used to simulate the flow-acoustic field results of high-speed trains under four ground simulation systems(GSSs):“moving ground+rotating wheel”,“stationary ground+rotating wheel”,“moving ground+stationary wheel”,and“stationary ground+stationary wheel”.By comparing the fluid-acoustic field results of the four GSSs,the influence laws of different GSSs on the flow field structure,aero-acoustic source,and far-field radiation noise characteristics were investigated,providing guidance for the acoustic wind tunnel testing of high-speed trains.The calculation results of the aerodynamic noise of a 350 km/h high-speed train show that the moving ground and rotating wheel affect mainly the aero-acoustic performance under the train bottom.The influence of the rotating wheel on the equivalent sound source power of the whole vehicle was not more than 5%,but that of the moving ground slip was more than 15%.The average influence of the rotating wheel on the sound pressure level radiated by the whole vehicle was 0.3 dBA,while that of the moving ground was 1.8 dBA.

基于改进长短时记忆网络的地面空调能耗预测

在机场运行管理中,地面空调是对飞机客舱进行降温除湿的主要设备,准确预测出其在工作过程中的耗电量对于建设绿色机场具有重要意义。地面空调能耗受多维因素的影响,为提高预测精度,提出一种基于改进双向长短时记忆(BiLSTM)神经网络的飞机地面空调能耗预测方法。所提方法使用BiLSTM神经网络和注意力机制构造模型的预测部分,可以充分挖掘和利用数据中的时间序列特征;并以预测精度最优为指标,提出一种基于改进蚁狮优化(IALO)算法的超参数优化算法,与标准蚁狮优化算法相比,改进蚁狮优化算法在随机游走空间缩小机制中改进了收缩因子并赋予收缩系数一定的随机性,同时引入普通蚁狮权重系数动态调整机制,提高所提算法的收敛速度及寻优能力。在实际数据集上进行仿真可知,所提方法预测结果的均方误差为6.045,平均绝对百分比误差为0.928%,决定系数为0.956。通过与其他多种预测方法比较,充分证明所提方法具有准确度高、适应性强等优点。

某纪念馆空调末端形式分析

为呈现扬州某纪念馆建筑本体效果、隐藏空调风口,采用2种空调末端形式:地板嵌入式空调器和风机盘管机组暗藏土建空腔内侧送风。对比分析地板嵌入式空调器与地板送风系统,对冬季幕墙内表面进行防结露计算,对风机盘管机组侧送风系统进行气流组织模拟计算,结果显示:纪念馆幕墙内表面温度≥11.2℃,大于室内空气露点(4.1℃),没有结露风险;采用侧送风空调形式,人员活动区域夏季室内温度约25℃,冬季约22℃,这2种空调末端形式既能满足人员舒适性需求又能巧妙隐藏空调设备。

南京某住宅小区温湿度独立空调系统设计应用

基于南京市一个采用温湿度独立空调系统的住宅项目,对此系统的热湿平衡进行了计算分析,并对冷热源系统和末端系统从节能经济性、运行特性、控制策略进行了研究。结合土壤热平衡模拟结果,采用适当的调峰措施,对地源侧需要设置冷却塔及开启热回收模式制取热水来辅助散热,以保证土壤总体热平衡进行了分析。对毛细管和新风系统各自承担的室内负荷比例计算和实施方式,根据项目每户每室实际可敷设毛细管面积,及毛细管管间距对单位面积的换热量影响,结合具体技术措施进行了可行性研究。同时跟常规多联机+燃气热水器系统进行了经济性对比分析,为业内同行在选择空调系统形式时提供参考。

基于地面桥载空调的飞机客舱温度系统建模及控制

针对基于地面桥载空调的民航飞机客舱温度控制中的系统建模问题,采用基于机理建模以及参数辨识相结合的方法,建立了系统的数学模型,并采用模糊PID进行了仿真控制实验。首先详细分析桥载空调给飞机客舱制冷的工作原理;在此基础上,通过线性化假设,机理建模以及参数辨识相结合的方法,建立系统模型;最后采用模糊PID控制算法,进行闭环控制仿真实验,实验结果证明了系统模型的合理性。该模型对从事飞机地面空调控制的研究具有参考意义。

Laboratory investigation of the anisotropic confinement-dependent brittle-ductile transition of a Utah coal

This paper was developed as part of an effort by the National Institute for Occupational Safety and Health(NIOSH)to identify risk factors associated with bumps in the prevention of fatalities and accidents in highly stressed,bump-prone ground conditions.Changes of failure mechanism with increasing confinement,from extensional-to shear-dominated failure,are widely observed in the rupture of intact specimens at the laboratory scale and in rock masses.In the previous analysis conducted in 2018,both unconfined and triaxial compressive tests were conducted to investigate the strength characteristics of some specimens of a Utah coal,including the spalling limits,the ratio of apparent unconfined compressive strength(AUCS)to unconfined compressive strength(UCS),the damage characteristics,and the postyield dilatancy.These mechanical characteristics were found to be strongly anisotropic as a function of the orientation of the cleats relative to the loading direction.However,the transition from extensional to shear failure at the given confinements was not clearly identified.In this study,a total of 20 specimens were additionally prepared from the same coal sample used in the previous study and then tested under both unconfined and triaxial compressive conditions.The different confining stresses are used as analogs for different width-to-height(W/H)ratios of pillar strength.Although the W/H ratios of the specimens were not directly considered during testing,the equivalent W/H ratios of a pillar as a function of the confining stresses were estimated using an existing empirical solution.According to this relationship,theW/H atwhich in-situ pillar behavior would be expected to transition from brittle to ductile is identified.

面向配电网接地故障暂稳态协同调控的UPQC优化运行方法

针对现有有源消弧装置存在稳态时直流侧取电难、直流电容难以稳压,暂态时接地故障瞬时过电压等问题,充分解析了接地故障全过程中统一电能质量调节器(unified powerqualityconditioner,UPQC)主动参与调控的潜力,提出一种面向配电网接地故障暂稳态协同调控的UPQC优化运行方法。将使用此方法的装置简称为具备消弧功能的统一电能质量调节器(arcsuppression-unifiedpowerquality conditioner,AS-UPQC)。首先,通过分析消弧稳态模式下AS-UPQC系统的功率流向,提出一种适用于AS-UPQC的能量主动平衡方法,通过控制AS-UPQC串联侧从电网吸收一定的有功来补偿并联侧消弧时消耗的有功。该方法在无需额外储能设备的前提下,有效保证了消弧装置直流侧电容能量平衡。其次,对接地故障的暂态模式进行分析,提出一种暂态响应优化的控制方法。在发生接地故障瞬间,控制串联侧从电网中吸收的有功,其等效增大系统阻尼,加快暂态过渡过程,从而抑制瞬态过电压的幅值。最后,通过仿真和实验验证了所提调控方法的有效性与可行性。

The Ceneri Base Tunnel＂ Construction Experience with the Southern Portion of the Flat Railway Line Crossing the Swiss Alps

This paper summarizes the experience that was gained during the construction of the 15.4 km long Ceneri Base Tunnel （CBT）, which is the southern part of the fiat railway line crossing the Swiss Alps from north to south. The project consisted of a twin tube with a diameter of 9 m interconnected by cross- passages, each 325 m long. In the middle of the alignment and at its southern end, large caverns were excavated for logistical and operational requirements. The total excavation length amounted to approx- imately 40 km. The tunnel crossed Alpine rock formations comprising a variety of rock typologies and several fault zones. The maximum overburden amounted to 850 m. The excavation of the main tunnels and of the cross-passages was executed by means of drill-and-blast （D＆B） excavation. The support con- sisted of bolts, meshes, fiber-reinforced shotcrete and, when required, steel ribs. A gripper tunnel boring machine （TBM） was used in order to excavate the access tunnel. The high overburden caused squeezing rock conditions, which are characterized by large anisotropic convergences when crossing weaker rock formations. The latter required the installation of a deformable support. At the north portal, the tunnel （with an enlarged cross-section） passed underneath the A2 Swiss highway （the major road axis connect- ing the north and south of Switzerland） at a small overburden and through soft ground. Vertical and sub- horizontal jet grouting in combination with partial-face excavation was successfully implemented in order to limit the surface settlements. The south portal was located in a dense urban area. The excavation from the south portal included an approximately 220 m long cut-and-cover tunnel, followed by about 300 m of D＆B excavation in a bad rock formation. The very low overburden, poor rock quality, and demanding crossing with an existing road tunnel （at a vertical distance of only 4 m） required special excavation methods through reduced sectors and special blasting techniques in order to limit the blast-induced vibrations. The application of a comprehensive risk management procedure, the execution of an intensive surface survey, and the adaptability of the tunnel design to the encountered geological conditions allowed the successful completion of the excavation works.

地源热泵户型蓄冰中央空调的探讨

针对目前国内空气源热泵户型中央空调存在COP值低、机组耗电量大 ,冬季融霜控制困难、室温波动大 ,机组无真正的能量调节 ,单相电机组额定制冷 (制热 )量太小 ,给用户带来不便 ,以及加剧了城市电网的供需矛盾等问题 ,提出了地源热泵户型蓄冰中央空调的解决方案 ,并探讨了双热力膨胀阀 ,双蒸发器和盘管外融冰的机组结构形式。还就我国城乡人民生活水平提高、住宅面积扩大和多样化、城市建筑景观和环境的限制、电力部门将推行居民家庭“峰谷电价”等方面 。

Tunnelling through weak and fragile rocks of Himalayas

A considerable amount of tunnelling has been going on in India for various projects such as hydroelectric power, irrigation, roads and railways. Most of these projects are located in Himalayas, far away from the urban areas. Tunnelling through weak and jointed rock masses such as the one in the Himalayas is a challenging task for the planners, designers, engineers and geologists because of high overburden, thickly vegetated surface, weak, poor and fragile rocks and highly varying geology with the presence of numerous small and big shear zones, faults, etc. Due to these reasons, various tunnelling problems have been faced in the past and are still being encountered. Failures and the problems may be regarded as challenges and opportunities for generating new knowledge base and thereby increasing self-reliance in tunnelling. The experiences of Himalayan tunnelling through weak and fragile rocks covering varying and mixed geology, understanding on tunnelling in squeezing ground conditions and applicability of TBM in Himalayas are presented. It has also been highlighted that the probe holes planning, drilling and monitoring shall be followed seriously to reduce the geological surprises.

飞机地面空调车自动温度控制系统设计

本文论述了飞机地面空调车自动温度控制系统的研究与开发。介绍了空调车的设计要求、功能及其原理。阐述了空调车动力系统和空调系统、环境参数对空调车温度及其稳定性的影响。该系统包括电源部分、信号检测、单片机及控制电路四部分。该系统是以单片机AT89C55为基础、采用电压/频率转换技术、具有计算机通讯功能的智能控温系统。

浅谈地源热泵在医院建筑中的应用

随着人们保健意识的日益提高,人们自然对医疗环境的要求也相应提高,对于现代化医疗建筑建设者来讲,营造生态保健型绿色医院就成为我们的努力方向,在现代医院建筑中引入绿色节能的地源热泵技术,使医院真正成为人类和谐舒适,环境优美,绿色生态的现代化疗养场所。因此,地源热泵系统在现代医院建筑中具有很大的应用价值,它将成为我国医院建筑节能领域重点推广的技术之一。

有窗密闭式猪舍水空调技术夏季降温效果

夏季高温严重影响母猪的繁殖性能和仔猪的成活率，蒸发降温方式因在降温的同时大幅增加舍内的湿度而影响使用效果。试验研究了北京地区有窗密闭式繁殖猪舍以地下饮用水为循环介质的水空调非蒸发降温系统的降温效果，并检测评价了水空调出水的水质变化及作为猪饮用水的适用性。结果表明：在舍外33～45℃的高温天气，安装水空调的试验猪舍在门窗开启的自然通风情况下舍内平均气温比舍外低4．2～11．3℃，比未安装舍的低1．2～2℃（P〈0．01），相对湿度高5．6％～7％；水空调出风口的风速1．24～2．10m／s，正对猪栏处风速0．13～0．23m／s；水空调舍内母猪的呼吸频率和直肠温度在低温和高温时段差异不显著（P〉0．05），有效降低了母猪在高温时段的热应激。经检测，水空调回水被轻微污染，不可直接作为猪饮用水，所以使用水空调需要定期清洗消毒。水空调降温单位面积运行电费（0．017元／m^2）低于湿帘—风机降温（0．039元／m^2）和民用制冷空调降温（0．157元／m^2）。因此，在地下水资源丰富的地区，水空调降温系统可以作为降温的有效手段之一。

电荷控制法研究a－SiCCD的电荷转移特性

提出一种更好地利用土壤冷源的新方法，即利用我国长江流域丰富的地表水作为排热场所和传热介质，以井作为竖直埋管形式，把土壤中的冷量提取到房间内的试验研究．测试结果包括不同埋管尺寸、不同水循环方式以及各种工况下运行参数对空调性能和排热量的影响．

地温空调成井工艺参数对地下水系统的影响

在对成井环节分析的基础上,识别了对地下水系统影响较为显著的成井工艺参数(即井径和滤水管孔隙率),基于地下水水热运移基本原理,建立了地下水流动和热量输运耦合模型。选取典型地温空调项目,通过设计不同成井工艺参数,模拟地温空调运行对地下水流场和温度场的影响。结果显示:不同井径和孔隙率在地温空调运行中,对地下水系统影响程度差别较大,井径对抽水井、回水井的影响比较明显,孔隙率对抽水井的影响大于对回水井的影响,适合安阳市地温空调的井径为30 cm、滤水管孔隙率为30%。

浅议辐射供冷空调系统在工程中的应用

根据对辐射空调系统特性的分析,介绍了其在实际工程中与其它空调系统的联合运行方式,包括与置换通风、独立新风和地源热泵等系统的联合应用,最后展望了辐射空调系统今后发展的前景,并提出了相应的建议。

台湾办公建筑冬季蓄能混合式地源热泵空调节能潜力分析

系统整理了台湾各地的平均地温,重点研究冬季蓄能混合式地源热泵(STES-HyGCHP)系统在台湾办公类建筑中的运行策略与节能潜力。在夏季和过渡季节的部分时间用地埋管取代冷却水塔,在冬季通过冷却水塔和地埋管联合运行带走土壤积蓄的热量并储存"冷"能,可解决土壤热容失衡问题也可提高空调主机效率。经过eQuest模拟和全年逐时迭代计算,在台南应用混合式地源热泵系统,模拟案例的全年空调系统耗能最高可降低5.85%,利用尖峰和离峰电价差,可实现电费降低7.44%,在台北这两项数值分别为3.21%和4.71%,并证实该系统为具备可持续运行的能力。地下水流动的影响和经济性在文中并未涉及。