深厚淤泥爆炸挤淤堆石坝稳定与沉降预测研究

【作者】 黄瑞梅；

【导师】 林从谋；

【作者基本信息】 华侨大学 ， 结构工程， 2009， 硕士

【摘要】 本文以深厚淤泥爆破挤淤法处理软基工程实际为研究背景,在大量文献调研的基础上,分析了深厚淤泥爆炸挤淤置换法填石堤坝的作用机理,提出了适合于由控制加载爆炸挤淤置换法形成、处于深厚淤泥中、断面形状复杂的填石堤坝的稳定性和沉降形变计算方法。应用该方法,首次对置换深度对稳定性的影响进行了分析。本文的主要工作和结论如下:1.通过对爆炸处理过程的分析研究发现,爆炸效应包括:排淤效应;降低了淤泥强度;定向滑移效应;爆炸“振陷”效应;抛石堤自身密实效应;爆炸排水等;2.软土地基在爆炸作用下产生的变形分为爆炸瞬间和爆后时期两个阶段。爆炸瞬间形成爆炸空腔,产生孔隙水压,地表产生一定沉降;爆后时期是超静孔隙水压的消散过程,同时也是土体发生较大沉降的过程。3.通过多种稳定性分析方法比较,选择合适的方法对堤坝断面的稳定性进行分析,并对影响堆石堤坝稳定性的因素进行分析研究,得到结论如下:(1)Bishop法与Janbu法的计算结果很接近,误差在10%以内,且稳定性系数较符合实际情况,而Bishop法计算速度较快,更具优势;(2)堆石坝堤顶堆载,淤泥的性质(C、Φ值),置换率(容重)等对堤坝稳定性影响较大。当其他参数不变时,安全系数随着堆载载荷的增大而减小,当堆载超过30KPa时,堤坝将处于失稳状态;随着水位的增加稳定系数也增加,但当水位达到一定高度后(约3.5米),稳定系数将不再提高;堆石坝置换需达一定置换率(容重≥18 KN/m3)方可稳定;(3)选择实际工程中具有代表性的断面,利用Bishop法进行分析计算。结果表明,各种工况下考虑爆炸挤淤对淤泥和坝下粘土的振密作用,各设计断面都是安全的,且多数断面的安全系数在1.4左右。此结果与设计及工程实际相吻合。4.通过多种沉降拟和曲线模型的比选,研究了沉降的规律并对沉降进行预测,得到结论如下:(1)引进灰色Verhulst理论,建立了深厚淤泥爆破挤淤筑坝的沉降量预测模型;(2)预测结果表明,爆炸挤淤置换法处理软基一般4-5个月即可达沉降稳定;(3)实际应用结果证明,灰色Verhulst沉降预测模型能有效地预测此种堤坝的变形沉降,具有理论与实用价值。更多还原

【Abstract】 Based on the engineering practice of soft foundation treatment by the toe-shooting method, this paper elaborated related research progress by reviewing plenty of published literature and technical documents, and analyzed the mechanism of the toe-shooting method with thick silt layer, and made stability analysis and settlement calculation of embankment with toe-shooting in deep silt layer and with a complex cross-section. This paper also proposed an efficient method to calculate the stability analysis and settlement of this kind of embankment. The main work and conclusions of this paper are listed as follows:1.It has been found by analyzed the treatment process of blast that the blast effects include the effect of toe-shooting, reduction of silt intensity, directional sliding effect, the effect of blasting“vibrated subsidence”, self-compacting effect of riprap, and blasting drainage.2.The deformation of soft foundation caused by blast has two stages: the blasting instantaneousness and the post-blasting stage. The blasting instantan- eousness forms blasting cavity and generates pore water pressure. The ground surface has some subsidence. The post-blasting stage is the process to dissipate the hyperstatic pore water pressure, and the soil has relatively larger subsidence at the same time.3.An appropriate method has been selected to analyze the stability of the dam cross-section after compared several methods of analyzing stability. It has been obtained the following conclusions by analyzing the factors to affect stability of rock-fill dam:(1).The calculation results of Bishop Method and Janbu Method are very close within the error at 10%. The stability coefficient of the two methods corresponds well with the actual situation. However, Bishop Method has more advantage due to faster calculation.(2).The loading at the top of rock-fill dam, silt properties(C andΦ) and replacement rate (density) impact on the stability of the dam relatively large. When other parameters are fixed, safety factor decreases as the loading increases. When the loading is more than 30KPa, the dam will be in an unstable state. The safety factor increases as the water level increases, but it will keep the same value after the water level is higher than 3.5m. The replacement rate needs to get to some value (density≥18 KN/m3) if rock-fill dam can be stable.(3).Some representative cross-sections have been selected, and analysis and calculation have been conducted with the Bishop Method. The results showed that the designed cross-sections are safe and the safety coefficients of most cross-sections are about 1.4 with consideration of the role of vibration of toe-shooting to silt and clay. The results coincide with the design and the actual engineering project.4.The settlement principle has been studied and the settlement amount has been predicted after compared several settlement fitting curves. The conclusions are listed as follows:(1).The gray Verhulst theory has been applied and a model to predict the subsidence of toe-shooting dam with thick silt layer has been built.(2). The prediction showed that it was taken 4-5 months for the settlement to be stable by using the toe-shooting method to treat soft foundation.(3). The application proved that the gray Verhulst theory could efficiently predict the settlement of this kind of dam. It has its theoretical and practical values.更多还原