A new equation for the equivalent hydraulic conductivity of rock mass around a tunnel

Author(s):  
Mahdi Zoorabadi ◽  
Buddhima Indraratna ◽  
Jan Nemcik
2004 ◽  
Vol 41 (5) ◽  
pp. 787-795 ◽  
Author(s):  
Robert P Chapuis

This paper assesses methods to predict the saturated hydraulic conductivity, k, of clean sand and gravel. Currently, in engineering, the most widely used predictive methods are those of Hazen and the Naval Facilities Engineering Command (NAVFAC). This paper shows how the Hazen equation, which is valid only for loose packing when the porosity, n, is close to its maximum value, can be extended to any value of n the soil can take when its maximum value of n is known. The resulting extended Hazen equation is compared with the single equation that summarizes the NAVFAC chart. The predictive capacity of the two equations is assessed using published laboratory data for homogenized sand and gravel specimens, with an effective diameter d10 between 0.13 and 1.98 mm and a void ratio e between 0.4 and 1.5. A new equation is proposed, based on a best fit equation in a graph of the logarithm of measured k versus the logarithm of d102e3/(1 + e). The distribution curves of the differences “log(measured k) – log(predicted k)” have mean values of –0.07, –0.21, and 0.00 for the extended Hazen, NAVFAC, and new equations, respectively, with standard deviations of 0.23, 0.36, and 0.10, respectively. Using the values of d10 and e, the new equation predicts a k value usually between 0.5 and 2.0 times the measured k value for the considered data. It is shown that the predictive capacity of this new equation may be extended to natural nonplastic silty soils, but not to crushed soils or plastic silty soils. The paper discusses several factors affecting the inaccuracy of predictions and laboratory test results.Key words: permeability, sand, prediction, porosity, gradation curve.


2017 ◽  
Vol 77 (4) ◽  
pp. 1663-1671 ◽  
Author(s):  
Vincenzo Piscopo ◽  
Antonella Baiocchi ◽  
Francesca Lotti ◽  
Emre A. Ayan ◽  
Alper R. Biler ◽  
...  

2021 ◽  
Vol 13 (13) ◽  
pp. 7161
Author(s):  
Oleg Bazaluk ◽  
Ivan Sadovenko ◽  
Alina Zahrytsenko ◽  
Pavlo Saik ◽  
Vasyl Lozynskyi ◽  
...  

The objective is to analyze the dynamics of the underground water of a mine field based on the study of the geofiltration process of the rock mass disturbed by mining to achieve safe extraction operations as well as subsurface territories at the stage of the mining enterprise closure. Numerical modeling, based on a finite difference method under the conditions of multifactority and definite uncertainty of processes of transformation of technogenic environment of a mine field, helps solve a problem concerning underground water dynamics forecasting. A hydrodynamic model of the M.I. Stashkov mine was developed while solving option series of epignosis problems in terms of the chronology of mine field stoping. The abovementioned made it possible to identify regularities of the history of filtration, the capacity parameters of rock mass and the expansion of areas of heightened hydraulic conductivity as well as to evaluate qualitatively the water balance components of a carbonic watered formation and an overlying one. The stage of mining closure helped obtain the forecasting hydrodynamic solutions. The efficiency of measures, concerning reduction of water ingress into mine workings and the mitigation of surface ecological effects of mine flooding was evaluated quantitatively. It was determined that implementation of the water control procedures makes it possible to perform a 10–38% decrease in water ingress. In this context, they may be applied both independently and simultaneously. In terms of mine closure and flooding, a period of complete underground water recovery takes three years; in the process, surface zones of potential waterlogging and swamping are developed within the floodplain of Samara River, located at the territory of Western Donbas (Ukraine). The scientific novelty is to define regularities of hydraulic conductivity transformation of the rock mass of a mine field starting from the mine working roof fall, up to its compaction during the mine operation period. To do that, nonstationary identification problems were solved, using numerical modeling. The abovementioned makes it possible to improve the reliability of hydrodynamic prognoses and develop technological schemes to control water at the state of the mine closure.


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