Knowledge Resource Center for Ecological Environment in Arid Area
| 防沙堤防护效益的初步研究 | |
| 其他题名 | A Preliminary Study on the Protection Effect of the Sand Dikes |
| 李建国 | |
| 出版年 | 2012 |
| 学位类型 | 硕士 |
| 导师 | 屈建军 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 流动性沙漠区的工农业发展、交通和民用建筑设施以及文化遗址的保护等直接推动着防沙工程的发展。随着我国国民经济的持续、稳定、高速发展，国家加大了对西部大开发的力度，交通运输的发展水平成为促进区域发展的重要因素。包兰铁路沙坡头段防沙工程的成功经验为世界防沙体系所借鉴，兰新高铁（兰新第二双线）建成后将大大缩短西北地区与中东部和西南地区的时空距离，对提高运营企业的运输组织效率、带动区域经济发展和提高人民生活质量具有重要意义。防沙堤在防护交通设施方面发挥着重要作用，本研究基于包兰铁路沙坡头段及兰新高铁玉门段作为野外观测场，然后通过室内风洞实验模拟进行风流场实验、积沙实验和压力实验，对不同类型防沙堤的防护效益进行了研究，最后通过FLUENT数值模拟方法进行验证，得出如下结论：（1）气流经过防沙堤时的能量区可划分为迎风坡脚低速区、遇阻抬升区、集流加速区、减速沉降区和消散恢复区五部分。阻沙作用的发挥主要利用迎风坡脚低速区对风沙流的滞留和背风侧有效防护距离区对风速的削弱。（2）梯形较三角形防沙堤能够在迎风侧形成更远的坡脚低速区范围；三角形较梯形防沙堤能够在背风侧形成更大的有效防护距离。实际工作中，三角形较梯形防沙堤修筑简单投资少，应根据防护工作的具体需要进行选择。两组形状防沙堤迎风坡接近堤身2/3高度处，是压力值正值与负值的转折点，此高度以下压力为正值，气流受阻；此高度以上压力为负值，气流顺畅。（3） 40°倾角三角形防沙堤达到最佳综合防护效益。各倾角三角形防沙堤形成的有效防护距离随风速的增大呈减小的趋势；各倾角三角形防沙堤形成的迎风坡脚低速区范围也随风速增大而减小。三角形防沙堤形成的有效防护距离范围随迎风坡倾角的增加而扩大。（4）两个形状相同、高度不等的三角形防沙堤，在各组风速下的防护效益类似；防沙堤形成的防护效益与堤体高度呈正相关，堤体高度越高，形成的防护效益越大；野外布置防沙堤的高度时，应充分考虑当地的边界层高度和被防护物的高度。（5）同组风速下,与主风向呈不同夹角的防沙堤体系，其他角度形成的迎风坡脚低速区和背风侧的有效防护距离均小于90°夹角时的范围，但呈90°夹角时不能导沙；当防沙堤走向与主风向不垂直时，虽然阻沙功效降低，但是能够发挥导沙功效；夹角呈30°和10°防沙堤虽然能很好地发挥导沙功效，但是阻沙功效不明显，且容易将风沙颗粒导向防护物；夹角呈60°时，防沙堤迎风坡一侧的剖面压力值介于0附近，能够很好地发挥阻沙功效，背风坡及堤顶能够很好地发挥导沙功能；考虑到布置防沙堤地点的风速情况，将防沙堤走向布置成与主害风呈60°夹角时能够最好地发挥防护功效；（6）30cm与60cm间距防沙堤体系形成的迎风坡脚低速区类似，且随风速增大而减小； 30cm间距防沙堤形成的有效防护距离大于60cm间距防沙堤体系，防沙堤体系的间距一般以4H左右为宜。 |
| 英文摘要 | The development of industry and agriculture, the protection of traffic and civil facilities, as well as the cultural sites in the moving desert areas have promoted the development of the sand-control systems. With the sustainable, steady and rapid development of our national economy, the state has increased the intensity of the Western Development. The transportation has played an important role in promoting regional development. The successful sand-control system of the shapotou section of the Baotou-Lanzhou railway has been referenced by the world sand-control systems. The Lanzhou-Xinjiang high-speed railway will sharply shorten the distance between the Northwest region and the Eastern and Southwest regions, improve the organizational efficiency of transport operating companies, promote regional economic development and improve people’s life quality after built. Sand dike plays an important role in the sand-control system. This study based on the field observation in the shapotou section of the Baotou-Lanzhou railway and the Yumen section of the Lanzhou-Xinjiang high-speed railway. Also, wind tunnel experiments and the FLUENT numerical simulation were conducted to simulate the protective effect of a series of sand dike models with different shapes, dip angles and heights. Results showed that：(1) Based on the flow characteristics, five typical flow fields could be roughly identified: low-speed area of windward slope toe, resistance-confronting lifting area on the windward flank, mass flow accelerating area above the top of the dike, flow-sinking decelerating area of leeward slope and dissipating recovering area, of which the low-speed area before the dike body and that on the lee flank of the dike could reduce wind speed and prevent sand. The low-speed area of windward slope toe and the low-speed area on the lee flank of the dike play an important role in weakening the wind speed. (2)Considering the area of low-speed area before the dike body, the trapezoidal sand dike was better than the triangular one, but from the aspect of the effective shelter distance, results were just the opposite. The triangular sand dike cost less in the actual situation. The 2/3 height of the dike body on the windward flank is the turning point of the pressure. Below this height, the pressure is positive and the wind is blocked; above this height, results were opposite. (3) The effective shelter distance of the triangular sand dike with a 40°dip angle was always the largest under the four different wind velocities. The protective effect of the triangular sand dike reduced with the growth of the wind speed. The effective shelter distance generated by the dike increased with the growth of the dip angle; while the area of low-speed area before the dike body decreased under like conditions. (4)The effective shelter distance on the lee flank of the sand dike correlated with the height of the sand dike. We should take full account of the local boundary layer height and the height of the protected materials at the actual situation. (5) The wind flow structures are similar under the three groups of wind velocities for the different sand dikes systems which have the different angles with the harm wind direction. When the sand dikes system is 90°angle with the harm wind direction, they generate larger low-speed area of windward slope toe and the low-speed area on the lee flank of the dike than other angles, but they cannot conduit the sand. While when the angle is 10°or 30°, they can conduit the sand perfectly, but they cannot resist the sand. When the sand dikes system is 60°with the harm wind direction, they cannot only conduit the sand ,but also resist them. So we the the 60°is the best design. (6) The sand dikes systems generate the same low-speed area of windward slope toe under the 30 centimeters and 60 centimeters space, but when the space is 30 centimeters, the system generate the larger low-speed area on the lee flank of the dike. So we think the best space between the sand dikes is 4times of the dike body. |
| 中文关键词 | 防沙堤 ; 风洞实验 ; 风流场 ; 防护机制 ; 有效防护距离 |
| 英文关键词 | sand dike wind tunnel experiment flow field protection mechanism effective shelter distance |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287092 |
| 推荐引用方式 GB/T 7714 | 李建国. 防沙堤防护效益的初步研究[D]. 中国科学院大学,2012. |
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