【作者】 李昊；

【导师】 闫增峰；

【作者基本信息】 西安建筑科技大学 ， 建筑技术科学， 2018， 硕士

【摘要】 宁夏须弥山石窟因风力侵蚀导致岩粒脱落,强烈的风化作用对石窟造成了严重的损坏。本文以营造有利于石窟保护的风环境为基础,对须弥山窟区风环境被动调节技术进行研究,主要工作如下:(1)论述须弥山石窟的历史价值以及现存状况,对须弥山石窟风化病害以及保护现状进行总结。对国内外在有关石窟风化以及风环境优化调节的研究进展进行了归纳,并提出本文研究内容和技术路线。(2)针对局部尺度室外风环境模拟中湍流模型的选择以及边界调节的设置进行分析。对不同风环境模拟软件进行对比,选择适合局部尺度规模下的模拟软件。(3)研究须弥山石窟窟区风环境特征,分别对窟区的风向、风速进行测试,并且通过PHOENICS软件模拟须弥山地形地貌对窟区风环境的影响,以及对比在有无绿化状况下的窟前广场风环境变化。数据表明:5号窟窟前主要风向为南向,风频比为0.3,其次为西北向和西南向,风频比分别为0.15、0.13。窟前风向比文管所风向稳定。当入流风向为北向、东北向、东南向、西向、西北向时,须弥山地形及地势对风速削弱作用0.2m/s~0.7m/s、对东风的风速没有影响、对南风和西南风的风速增强作用为1m/s~3.2m/s。窟前广场区域在无绿化时风速为3.21m/s,有绿化时风速为3.18m/s。风速比的大小受窟区绿化的影响,但在入流风速分别为3.3 m/s和4.5m/s情况下,4)的值分别为0.964和0.978,两者仅变化0.014。(4)尝试从减弱石窟风化强度的角度出发,针对降低窟前平均风速提出以下风环境被动式调节策略:建议防风林带栽植油松等当地常见高大乔木,增加防风林带高度使其达到25m。调整林带与崖体距离为50m,使防风林带走向为东南偏南向,增加防风林带的叶面积密度使其达到4。在5号窟西侧设置东南偏南向走向、高度35m、坡度为60°的防风构筑物,构筑物底部延伸长度为20m。通过数值模拟方式证明通过上述被动优化调节设计,对主害风向为西南风的风速减小值可达到3.05m/s,与未设置防风林带以及防风构筑物相比时,风速减小70.9%,进而达到了降低风速减弱风化强度的目的。更多还原

【Abstract】 Xumi Grottoes in Ningxia have been caused serious damage due to the strong wind erosion in the surface of the rock and the wind erosion caused the loose rock particles to fall off.Based on the construction of a wind environment conducive to the protection of grottoes,this paper studies the wind environment of the Xumi Grottoes.The main work is as follows:（1）This paper introduces the historical value and existing status of the Xumi Grottoes and summarizes the wind erosion of the diseases and protection status of the Xumi Grottoes.At home and abroad,this paper summarizes and analyzes the researches on erosion of the grottoes and the optimization of the wind environment,summarizes the previous research experience and puts forward the research methods and technical route of this paper.（2）The selection of turbulence model and the setting of boundary regulation in mesoscale outdoor wind environment simulation are analyzed.The simulation software of different wind environment was compared,and the simulation software suitable for mesoscale conditions was selected.（3）In order to study the characteristics and causes of the winds in the Xumi Grottoes,the wind direction and wind speed of the area were comparatively tested,and the influence of the topography of the Xumi Grottoes on the wind environment was simulated by PHOENICS software.By comparing the wind environment in the cave front plaza in the presence or absence of greening conditions,this paper points out the effect of the greening in the cave area on the wind environment.The result of test and simulation comparison are as follows:The main wind direction in front of Cave No.5 is southward,with an air ratio of 0.3,followed by the northwest and southwest directions,and the wind frequency ratio is 0.15 and 0.13 respectively.Wind direction change rate in front of grottoes is lower than the cultural relic management office.The topography effects to the direction of north wind,northeast wind,southeast wind,west wind,northwest wind were between 0.2m/s and 0.7m/s、has no effect on east wind speed、the enforcement effect on the south wind and southwest wind speed between 1 m/s and 3.2 m/s.In front of the plaza,the wind speed was 3.21 m/s in the absence of greening,and 3.18 m/s in greening.The wind speed ratio is affected by whether there is greening in the cave area.The wind speed ratio is affected by whether there is greening in the hole area,but when the inflow wind speed is 3.3m/s and 4.5m/s respectively,the value of₄)is 0.964 and 0.978 respectively,and the difference between them is only 0.014.（4）From the perspective of cultural relics protection,the following suggestions are proposed for the adverse wind environment in the cave areas:Increase the height of windbreak belts to 25m.It is recommended that windbreak forest belts be planted with three kinds of common tall trees,such as Pinus tabulaeformis,and adjust the distance between forest belts and cliff to 50m,The windbreak forest belt tends to be south-southeastward,increasing the degree of protection of the windbreak forest belt,making it suitable for the leaf area density to be about 4.In the west side of the cave 5,a wind protection structure with a south-south direction and a slope of 60°is added.The length of the bottom of the structure is 20m.The passive optimization and design of the windbreak belt was proved by numerical simulation.The wind speed of the main wind direction to the southwest wind direction was reduced by 3.05m/s.更多还原