【作者】 马晨光；

【导师】 韩晓雷；

【作者基本信息】 西安建筑科技大学 ， 岩土工程， 2011， 硕士

【摘要】 潜水含水层的渗透系数和影响半径,是基坑降水设计中两个重要的水文地质参数,其精确程度会直接影响基坑降水设计的可靠度。测定渗透系数和影响半径一般采用野外抽水试验。目前,生产实践中多是根据稳定流抽水试验公式来确定潜水含水层渗透系数和影响半径。但是,这种抽水试验一般需要较多的勘探及试验工作量,不是在任何情况下都有条件进行的。随着地下水非稳定流运动理论的发展和应用,人们越来越多的开始使用非稳定流公式来计算潜水含水层参数。本文结合稳定流和非稳定流理论,对潜水完整单井抽水无观测孔和有一观测孔两种情况下渗透系数和影响半径的求解方法进行了分析和探索,指出了常规计算方法的不足之处,并给出了本文的求参方法。最后,利用西安北客站场地抽水试验资料对上述求参方法进行计算,并与两个观测孔的稳定流公式计算结果进行对比验证,从而证明了本文方法的合理性和经济实用性。通过本文的分析研究,可以得出以下结论:1.在潜水完整单井抽水无观测孔情况下:①采用传统方法(裘布衣公式和经验公式迭代)求解渗透系数和影响半径是缺乏理论根据的;②当抽水井的水位降深较大时(0.1H<s_w <0.3H,其中H为潜水含水层厚度,s_w为抽水井水位降),采用降速法求解渗透系数时会与实际情况会产生一定的偏差;③当抽水井水位降s_w小于0.3H时,采用抽水井水位恢复法求解渗透系数和影响半径时与实际情况基本一致。2.在潜水完整单井抽水有一观测孔情况下:①采用稳定公式求解渗透系数和影响半径时与实际情况比较一致,但是此法需计算井损值,因此至少要做三次稳定抽降,工作量比较大;②采用观测孔直线斜率法求解渗透系数时会与实际情况会产生一定的偏差;③采用观测孔水位恢复公式和等代大井公式联立求解渗透系数和影响半径时与实际情况基本一致,而且该方法避免了求解井损值。因此,对于潜水含水层的渗透系数和影响半径,在潜水完整单井抽水无观测孔情况下,建议采用水位恢复法求解;在潜水完整单井抽水有一观测孔情况下,建议采用观测孔水位恢复公式和等代大井公式联立求解。更多还原

【Abstract】 The permeability coefficient and radius of dewatering influence of phreatic aquifer, the degree of accuracy of which have a direct impact on reliability of excavation dewatering design, are two important hydrogeological parameters in excavation dewatering design. The determination method of permeability coefficient and radius of dewatering influence is field pumping test. At present, steady flow pumping test is often used to test the permeability coefficient and radius of dewatering influence of phreatic aquifer in practice. But the test method needs much exploration and test wrok, which is often diffcult to realize.With the development and application of unsteady theory of the motion of ground water, more and more unsteady flow formula is used to find the solution of phreatic aquifer parameters. In the two cases of pumping in interferentical single well of phreatic without and with observation holes, the paper study the solution method of permeability coefficient and radius of dewatering influence according to the theory of stable and unstable flow, pointing out the shortcomings of common methods and giving methods how to solve parameters. At last , the aforementioned methods are verified by filed pumping test data in Xi’an north station, and compared to the result of steady flow pumping test formula of two observation wells, proofing the rationality and practicability of methods of this paper.Through study of the paper, some conclusions can be made as follows: 1. In the case of pumping in interferentical single well of phreatic without observation holes:①Using conventional method(iterative method of Dupuit, J. -J. formula and emprical formula ) to solve permeability coefficient and radius of dewatering influence is short of the theory evidence;②When having more drawdown of pumping well(0.1H<s_w <0.3H,H-thickness of phreatic aquifer, s_w -drawdown of pumping well ), it well have some ww amount of deviation compared with the actual situation using speeddown method to solve permeability coefficient;③Using recovery theory of pumping well to solve permeability coefficient and radius of dewatering influence is concordant with the actual situation, which is premise with drawdown of pumping well of belowing 0.3H. 2. In the case of pumping in interferentical single well of phreatic with one observation hole:①Using steady flow formula to solve permeability coefficient and radius of dewatering influence is concordant with the actual situation, however, which needs calculating well loss, so at least carrying out three times steady draw-off with much work;②Using straight line slope method of observation hole to solve permeability coefficient has some amount of deviation compared with the actual situation;③Combining with recovery theory formula of observation hole and equivalence of big well formula to solve permeability coefficient and radius of dewatering influence is concordant with the actual situation, without calculating well loss. Thus, for permeability coefficient and radius of dewatering influence of phreatic aquifer, in the two cases of pumping in interferentical single well of phreatic without and with observation holes, the former suggests adopting recovery theory to solve, the latter suggests adopting the method of combining with recovery theory formula of observation hole and equivalence of big well formula to solve.更多还原