昆明南市区地面沉降研究

【作者】 孟国涛；

【导师】 李峰；

【作者基本信息】 昆明理工大学 ， 矿产普查与勘探， 2003， 硕士

【摘要】 根据1987-1998年四期全网水准测量数据重新绘制的地面沉降等值线图显示，昆明市存在明显的地面沉降现象。沉降区主要位于南市区，总沉降面积达180km2，已形成2个明显的沉降漏斗区域，即广卫村-小板桥-飞机场沉降区及渔户村-福海沉降区，其中小板桥沉降中心累计沉降量最大，累计沉降量达236． 2mm。此外，地面沉降加速、扩张趋势明显。昆明南市区地下水的赋存、分布和运动，受该区地层岩性、地质构造、地貌和新构造运动的综合控制。孔隙水赋存于晚新生代松散沉积层的孔隙中，具多个含水层，连续性差；岩溶水赋存在古生界碳酸盐岩基岩岩层中，分布面积广、厚度大、富水性较强，是昆明地区最重要的地下水类型，受人为开采影响，局部区域水位下降快。南市区第四系地层结构变化大，非成带湖积相沉积土固结程度低，软、粘土性质及各向异性性质显著，浅层土体工程性状差。这样的水文地质工程地质条件是地面沉降发生和发展的地质因素，是地面沉降既有特征的内在原因。南市区地面沉降的诱发因素主要有地下水的抽汲、土体的自然固结压密、新构造运动、建筑荷载与工程施工。各诱发因素与地面沉降关系如下：(1) 由于昆明南市区的地面沉降属于断陷盆地模式，第四系土体与基岩的接触边界为非贮水边界，第四系含水层与基岩含水层连通，抽汲岩溶水会造成第四系土体的固结压缩。基岩水位的大幅度下降是控制沉降中心的重要原因。(2) 随着城市化进程，南市区的建筑密度、建筑容积率增加较快，新建的建筑比例较高，加上区内浅层土体工程性质差，直接导致工程建设的地面沉降效应凸显，成为地面沉降的又一重要制约因素。(3) 南市区地面沉降漏斗位于滇池湖盆北缘的湖沼沉积平原地貌单元上。属于古滇池沉积区。沉降区由湖演变为陆的历史不长，整个第四系是一套固结程度低的松散堆积，具备自重压密条件。此外，泥炭层的有机质氧化加速着土体的自然固结。(4) 区内新构造运动较为强烈，直接造成区域性升降。由于各种地面沉降的制约因素在不同区域的作用与地位不同，且主导因素并非一成不变。本文引入模糊综合评判及聚类分析得出区内地面沉降制约因素综合评判权重依次为：抽汲地下水为72％，建筑荷载11％，工程施工7％，土的天然固结9％，新构造运动1％。最后，在阐明地面沉降机理的基础上，本文对南市区地面沉降进行了预测，并基于地面沉降制约因素的情况提出了防治建议。更多还原

【Abstract】 According to the datum of the second grade leveling from 1987 to 1998, significant land subsidence was found in Kunming city. The south Kunming city is the dominating area of land subsidence, whose total area is 180 km2, and has formed two very prominence infundibular areas. The one is located in Guangwecun-Xiaobanqiao-Wujiaba airport, the other is around Yuhucun-Fuhaicun. The most prominence subsidence area is Xiaobanqiao center, which amounted to 236.2mm(from 1987 to 1998). What’s more, the land subsidence is accelerating and expanding.In south Kunming city, stratum, lithographic characters, tectonics, geomorphology and neotectonism influence the groundwater’s existence, distributing and seepage. Void water is affluent in the lake deposit void of Cainozonic, which has multiplayer structure, and is discontinuous. Karst water is affluent in carbonatite rock formation of Palaeozoic, which formation are abroad, thick, and watery. The Karst water is the most important type of groundwater in South Kunming, and its water level is fleetly falling in some areas where lies a great number of pumping wells. On the other hand, in South Kunming, the Quaternary soil is soft and clayey, stratum structures vary a lot, the engineering character of shallow soil is badness, and lacustrine-clay soil has marked anisotropy characteristic. In short, the hydrogeology conditions and the engineering geology conditions are vital geological factors, which influence the occurrence and development of land subsidence, and lead it to be what it is currently.Groundwater pumping, architecture loading, constructing, soil nature concretion and neotectonism are together playing an important role on land subsidence. Each complication has its connection with land subsidence: (1) Because the pattern of land subsidence in South Kunming is dislocation basin pattern, the interface between Quaternary soil and bed rock cannot separate ground water, so that the void water-bearing bed may communicate with karst water-bearing bed. Pumping karst water can render the concretion of Quaternary soil. Where the level of karst watermay communicate with karst water-bearing bed. Pumping karst water can render the concretion of Quaternary soil. Where the level of karst water falls a lot on the edge of basin, there is a prominence infundibular area. (2) With the city’s expanding, architecture’s consistency and cubage increase swiftly and violently, and the proportion of newly-built architecture is most. What’s more, the engineering character of shallow soil is badness, all of the above magnify the architecture loading’s effect on the land subsidence. (3) The infundibular area of land subsidence is located in the brim of lake basin, where is the area pristine Dianchi lake, and it is become land not long ago. The whole Quaternary Period lacustrine-clay soil is very soft, gravitational concretion is going on. On the other hand, lack peat’s oxidation accelerates concretion. (4) In the investigative area, Neotectonism is activities, which straightly result in the land subsidence. Because different complication has different effect, and the dominant complication is not fixedness. This paper introduce fuzzy judgment and classified analysis to probe into all of the complication, and working-out their shares as follow, pumping groundwater account for 72%, and architecture loading account for 11%, and constructing account for 7%, and soil nature concretion account for 9%, and neotectonism account for 1%.At last, based on the mechanism of land subsidence in South Kunming, this paper has forecasted the extendecy of the land subsidence, and putted forward some preventive advice.更多还原