ICE - Institution of Civil Engineers - Virtual Library

7098 DISCUSSION Unsteady unconfinedflow to gravity wells J. A. FOX i 1. ALI 3 Dr T. R. E. Chidley, University of Aston in Birmingham There appears to have been a recent surge of interest in the problem of flow around wells both in this country and abroad. I have just returned from the Middle East where I have been engaged in the design and analysis of multi-well irrigation schemes. This involvement with the problem has further shownthe real need for more research on it; in meeting this need the Authors are to be congratulated...

7098 Unsteady unconfinedflow to gravity wells Shallow-water wave theory can be used to describe unsteady flow through porous media. The significant point of difference between this application and more usual ones is the much greater friction losses experiencedby a fluid when moving through the such media. As in all problems using shallow-water wave theory solution involves the integration of a pair of quasilinear hyperbolic partial differential equations and for a digital computer a modification of the method of characteristics programed wasthetechniquechosen.Goodagreementbetweentheoreticalandexperimental valueswasobtained.Because the single-wellproblemissymmetrical a 15" sector A tank wasbuiltwith the plan shape of a 15" sector of a onlywasinvestigated...

7272 DISCUSSION Resistance network for threedimensional unconfined groundwater problems with examples of deep well watering K. R. RUSHTON & R. HERBERT Dr N. S. Boulton, Emeritus Professor, University of Sheffield The Paper describes a powerful method of analysing complicated groundwater problems, but the accuracy of the results depends on the correctness of the basic assumptions, of which probably the most questionable is the assumption that the storage coefficient S is constant. 76. The analyses of many pumping tests in sedimentary unconfined aquifers have shown a largeapparent increase of S with time during the test, which is probably due to the slow draining or delayed yield of the aquifer above the falling water table...

7029 Comparative analysis of data from pumping tests in an unconfined aquifer Four pumping tests carried out in the Cityof Antwerp are analysed by a number of well-known techniques to obtain quantitative assessmentof the hydraulic properties of the unconfined sand aquifer. A brief review is made of the principles of pumping tests and of the common methods of analysis, whichare compared in respect of their applicability and ease of use. The values of the formation constants computed from the test data indicate that aquifer properties of the right order of magnitude can be predicted by most of the methods discussed but that more exact agreement cannotin general be achieved...

7029 DISCUSSION Comparative analysis of data from pumping tests in an unconfined aquifer E. W. BRAND Mr P. Johnson, Civil Engineering Department, University of Newcastle upon Tyne In his Paper, Dr Brand makes only one brief mention of the possible occurrence of river recharge into anunconfined aquifer brought about by pumping of groundwater from the aquifer. He doubtless considered this possibility during the analysis of data from the City of Antwerp, and I would therefore ask how heconcludes that the River Schelde did not influence water levels during borehole observations? Perhaps the estimated radii of influence of the pumped wells were much less than the wells' distances from the river? (The linear scale of Fig...

564 BOULTON ON THE DRAWDOWN OF THE WATER-TABLE Paper 5979 "The Drawdown of the Water-Table under Non-Steady Conditions near a Pumped Well in an Unconfined Formation " by Norman Savage Boulton, M&., M.I.C.E. (Ordered by the Council to be published with written discussion)? SYNOPSIS A new equation is obtained for the drawdown of the water-table near a pumped well in an aquifer of any thickness and permeability, under non-equilibrium conditions. Tables of the mathematical functions involved make the equation simple to use in practice...

7272 Resistance network for threedimensional unconfined groundwater problems w i t h examples of deep well dewatering K. R . R U S H T O N , PhD. MICE' R. HERBERT, PhD* The Paper discusses theuse of the electrical resistance network in analysing complex unconfined groundwater flowproblems.Thefirstpartisconcernedwiththetechniques of representing the aquifer, wells and cut-off walls and also stationary and movingwatertables. In thesecondparttheproblemofdeepwelldewateringis considered. A design method is proposed and design curves are presented; these are checked against a dewatering case history. Notation beginning and end of fast phase scaling factor mesh interval h piezometric head undisturbed water table height he pumped well water level hw k permeability ktlsh, non-dimensional time N number of wells discharge rate Q radius of well rw effective pit radius rp R electrical resistance S dimensionless storage coefficient drawdown at end of fast phase Sllrn design drawdown Sdes time t T time to dewater V velocity of water table fall electrical voltage V v1 0 volume of water to be removed during dewatering X , Y , = co-ordinates A, B C d Introduction The controlof groundwater by pumping wells is important t o civil engineers...

CORRESPONDENCE 213 CORRESPONDENCE on a Paper published in Proceedings, Part I I August 1954 I, Paper No. 5979 `l The Drawdown of the Water-Table under Non-Steady Conditions near a Pumped Well in an Unconfined Formation " t by Norman Savage Boulton, M.Sc., M.I.C.E. Correspondence Mr J. Ineson (Water Division, Geological Survey) congratulated the timely presentation of the Paper. Since the original Author on his analysis by Theis1 of non-steady conditions of 00w in an artesian aquifer, there had been a need for a precise mathematical treatment of non-steady flow around a discharging well under water-table conditions...

Some drawbacks affecting the variable mesh finite element solution of unconfined flow problems are discussed and a procedure is suggested aimed at avoiding them in steady state and transient analyses. In particular, it is shown that the results of standard algorithms often used in practice may present spurious oscillations of the phreatic surface in the vicinity of the intersection with a pervious boundary exposed to the atmosphere. They may become exceedingly large when a limited number of elements is adopted in the mesh, and in some cases lead to non-correct final (steady state) configurations of the free surface. In order to eliminate this negative effect from the finite element analysis, a simple criterion is suggested based on an algorithm for non-linear function minimization. Some applications of this technique are presented to two- and three-dimensional unconfined problems.

L'article discute la solution à éléments finis de mailles variables des problèmes d'ecoulement sans contrainte latérale et propose une procèdure pour éliminer ses inconvenients dans les analyses sta-tionnaires et transitoires. En particulier on dé-montre que les résultats des algorithmes normaux souvent employés en pratique peuvent faire apparaitre des oscillations fausses de la surface phreatique dans le voisinage de l'intersection avec une limite perméable exposée à l'atmosphère. Ces oscillations tendent à devenir excessives lorsque la maille comprend un nombre limite d'éléments, de sorte qu'on obtient parfois des configurations finales (stationnaires) de la surface libre qui sont incorrectes. Pour éliminer cet effet négatif des analyses avec éléments finis, Particle propose un critère très simple basé sur un algorithms pour la minimalisation fonctionnelle non-linéaire. Des exemples sont donnés de l'application de cette technique aux problèmes bidimensionnels et tridi-mensionnels sans contrainte latérale.

The effect of the pre-treatment of plating wastes added to commercial Portland cement on the unconfined compressive strength and the setting time of the cement/waste products has been studied. The raw wastes were a sludge and a cake generated in a plating industry after the treatment of a liquid effluent by means of a physico-chemical process. From the raw waste, two pre-treated wastes were produced: a dry material obtained after thermal treatment at 105°C, grinding and sieving the raw waste; a calcined obtained after thermal treatment of the former material at 1000°C. The cement replacement ranged from 1 to 5 % dry wt of waste. The setting time of products was between 2 and 6 times higher than cement for the sludge and the dried waste products; however, the setting time of the cement/calcinated waste products was similar to that of cement. The unconfined compressive strength of cement/calcinated waste products was in the range of the cement (CEM I 42.5 R) as stated in the Spanish standard UNE 80301:96: minimum 42.5 MPa and maximum 62.5 MPa. However, the cement/sludge products only fulfilled the limits for products containing 1 % waste.

• Introduction

• Experimental Method

• Results and Discussion

• Conclusions

• References