Subjects: Geosciences >> Geography submitted time 2024-05-20 Cooperative journals: 《干旱区地理》
Abstract：以提取1990—2020年植被覆盖度、遥感生态指数、人类干扰指数等遥感生态指标来反映塔里木河干流生态输水工程实施前后，生态状况变化趋势。将遥感生态指标作为驱动因子，提出一种改进的生态系统服务价值计算法，量化供给、调节、支持、文化功能的生态系统服务价值，分析各功能间权衡和协同效应的动态演变关系，对1990—2020年累积生态效益进行估算。结果表明：（1）生态输水以来，干流有近1/3的区域植被覆盖度增加，较低、中、较高、高植被覆盖度面积占比分别增加17%、5%、2%、2.9%。（2）上游生态系统服务价值先增加后渐趋稳定，中、下游生态系统服务价值先增加后减小再增加，表明中、下游对生态输水的响应存在一段滞后期，且受来水水量影响较大。（3）调节和支持功能之间存在协同效应，供给与调节和支持功能之间存在权衡效应。（4）生态输水后期，干流上、中、下游累积生态效益均表现出“边际效益递减规律”，据此从生态修复角度出发，给出断面年径流量的适宜范围，上游不超过42.5×108 m3，中游不超过21.5×108 m3，下游不超过3.5×108 m3。研究结果可为优化生态水水量配置提供科学指导。
Subjects: Mechanics >> Basic Mechanics submitted time 2023-04-24 Cooperative journals: 《应用力学学报》
Abstract： In water transportation projects,due to the constraints of topography and geology,bifurcated pipelines have been widely promoted and applied.The leakage of bifurcated water pipelines is an important issue of great concern to scholars at home and abroad,and the transient flow method is one of the most efficient,accurate and fast leak detection methods at present.Based on this,this paper constructs a transient flow model of water pipeline with bifurcation structure,and explores the influence of different factors on the pressure change at the end of the valve.The factors affecting the pressure change at the end of the valve were investigated.The results show that the difference of pressure curve increases with the increase of the length of bifurcation pipe,the attenuation rate of pressure curve decreases with the increase of valve closing time,and the leakage has little influence on the variation period of pressure curve.The leakage position is different,the shape of the pressure curve at the amplitude is different.When the leakage position is in the upper half of the pipeline,the curve will be convex at the amplitude,and when it is in the lower half of the pipeline,the curve will be concave at the amplitude trend.
Subjects: Mechanics >> Applied Mechanics submitted time 2023-03-20 Cooperative journals: 《应用力学学报》
Abstract： Tunnel construction in karst area often faces geological disasters such as water inrush , especiallyfor the construction of shallow tunnel under river , which is a very challenging work. Due to the in situ faultfracture zone , high weathering degree of rock mass , and the development of joints and fissures in the tunnelsite , the possibility of river water intrusion into the tunnel is greatly increased. In order to effectively evaluate the risk of water inrush in karst shallow tunnel under river, according to the geological conditions andtunnel characteristics of the tunnel site,11 factors affecting the water inrush , such as formation lithology,modified strata inclination, soluble and insoluble rock contact zones , surrounding rock grade , fault zonewidth ,fault property , fissure development degree , surface water flow , surface catchment area, buried depthof tunnel , construction disturbance degree , are selected as the evaluation indexes , and the risk evaluationsystem of karst shallow tunnel under river is established.The analytic hierarchy process (AHP) was usedto construct judgment matrix to determine the weight of evaluation indexes , the set pair analysis methodwas used to calculate the connection degree of each evaluation index , and then the comprehensive connec-tion degree of evaluation samples was determined.Secondly , the maximum membership degree principlewas used to identify the risk level of water inrush.Finally , according to the corresponding relationship be-tween the risk level and the water inflow, the scope of water inrush inflow can be preliminarily predicted.ln view of the risk of water innush in shallow buried section of Yuelongmen Tunnel under-crossing Gao-chuan River , the set pair analysis model was used to analyze the risk. 'The calculation results show that therange of water inrush volume predicted by the risk assessment is 3 000 ~ 10000 m'/d,and the actual waterinflow from site excavation is 7 000 m'/ d. That is to say , the results of risk assessment are basically con-sistent with the actual situation , which verifies the rationality and feasibility of the evaluation system andmethod and provides effective support for risk assessment of water inrush of karst shallow tunnel underriver.
Hits
Hits
Downloads
Comment
YES