scholarly journals Settlement Analysis of a Confined Sand Aquifer Overlain by a Clay Layer due to Single Well Pumping

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Wen-jie Niu ◽  
Zhenyu Wang ◽  
Feng Chen ◽  
Hongran Li
Keyword(s):  
Analytical Solution ◽  
Confining Pressure ◽  
Vertical Force ◽  
Clay Layer ◽  
Sand Aquifer ◽  
Consolidation Settlement ◽  
Single Well ◽  
Primary Consolidation ◽  
Pudong New Area ◽  
3D Finite Element Method

This paper proposes a simplified analytical solution to determine the primary consolidation settlement of a confined sand aquifer overlain by a clay layer due to single well dewatering. After single well pumping in a steady state, the Dupuit equation predicts the confined sand aquifer water head drawdown. The confining pressure on the underlain confined sand aquifer top surface is determined using the principle of vertical force equilibrium. Additional vertical stresses in each layer of the confined sand aquifer are then computed with the Boussinesq solution. The overall aquifer consolidation deformation is then determined with thee-lgpcurve from the one-dimensional consolidation test and the applied vertical stress with the integral method. The proposed analytical solution is validated using the ADINA software, where porous media are simulated with the Biot model and solved with the 3D finite element method. This proposed analytical solution is used to simulate the primary consolidation settlement due to well pumping, using the fourth confined aquifer in the Pudong New Area of Shanghai from 1980 to 1995 as a case study. The predicted settlement compares reasonably well with the actual measured settlement in Shanghai.

scholarly journals Push-pull tests for estimating effective porosity: expanded analytical solution and in situ application

2017 ◽  
Vol 26 (2) ◽  
pp. 381-393 ◽  
Author(s):  
Charles J. Paradis ◽  
Larry D. McKay ◽  
Edmund Perfect ◽  
Jonathan D. Istok ◽  
Terry C. Hazen
Keyword(s):  
Analytical Solution ◽  
Center Of Mass ◽  
Unconfined Aquifer ◽  
Effective Porosity ◽  
Pull Test ◽  
True Value ◽  
Single Well ◽  
Pull Tests ◽  
Injection Phase

Abstract The analytical solution describing the one-dimensional displacement of the center of mass of a tracer during an injection, drift, and extraction test (push-pull test) was expanded to account for displacement during the injection phase. The solution was expanded to improve the in situ estimation of effective porosity. The truncated equation assumed displacement during the injection phase was negligible, which may theoretically lead to an underestimation of the true value of effective porosity. To experimentally compare the expanded and truncated equations, single-well push-pull tests were conducted across six test wells located in a shallow, unconfined aquifer comprised of unconsolidated and heterogeneous silty and clayey fill materials. The push-pull tests were conducted by injection of bromide tracer, followed by a non-pumping period, and subsequent extraction of groundwater. The values of effective porosity from the expanded equation (0.6–5.0%) were substantially greater than from the truncated equation (0.1–1.3%). The expanded and truncated equations were compared to data from previous push-pull studies in the literature and demonstrated that displacement during the injection phase may or may not be negligible, depending on the aquifer properties and the push-pull test parameters. The results presented here also demonstrated the spatial variability of effective porosity within a relatively small study site can be substantial, and the error-propagated uncertainty of effective porosity can be mitigated to a reasonable level (< ± 0.5%). The tests presented here are also the first that the authors are aware of that estimate, in situ, the effective porosity of fine-grained fill material.

Analysis on the Influence of the Primary Consolidation Settlement of the e~p Curves and the Soil Bulk Density of the Soft Soil Foundation

2014 ◽  
Vol 919-921 ◽  
pp. 645-648 ◽  
Author(s):  
Wen Shuang Wang ◽  
Jiong Qi Yu
Keyword(s):  
Bulk Density ◽  
Soft Soil ◽  
Soil Bulk Density ◽  
Correction Coefficient ◽  
Consolidation Settlement ◽  
Primary Consolidation ◽  
Soil Foundation ◽  
Soft Soil Foundation ◽  
Compressible Soil ◽  
The Impact

In general, primary consolidation settlement of soft foundation is calculated by layerwise summation method considering the design load in seawall engineering design, and the total settlement is obtained by multiplying a settlement correction coefficient which is difficult to select. In this paper, one seawall engineering case is enumerated, the impact on the thickness of compressible stratum and the primary consolidation settlement is studied by considering the changes of the e~p curves of the soft soil foundation. The results indicate that the thickness of the compressible stratum changes obviously for different stress ratio owing to the difference of the soil bulk density of the compressible soil, and the primary consolidation settlement has corresponding change tendency according to the shape of the e ~ p curves and the soil bulk density of the compressed soil. At last, this paper suggests that a designer can weaken the weight of settlement correction coefficient based on the analysis of the influence of primary consolidation settlement with different e ~ p curves of the soft soil foundation in future design.

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