Estimating hydraulic conductivity from piezocone soundings

Abstract

A method for estimating the hydraulic conductivity of soils from piezocone penetration tests is suggested in this paper. By invoking Darcy's law over the finite time required for an increment of cone penetration, it is argued that there will be some water movement through the soil around the cone, albeit very small if the soil is very fine grained. Based on this argument, and noting the comprehensive test data collected previously by Elsworth & Lee, a bi-linear relation between the dimensionless piezocone sounding metric BqQt and the dimensionless hydraulic conductivity index KD plotted on double logarithmic scales has been proposed for soils ranging from sands to clays. It is demonstrated that these revised relationships can be used to evaluate plausible values of hydraulic conductivity from piezocone sounding records taken at two different clay soil sites in Saga and Yokohama, Japan. The major significance of this work is in extending the range of application of the method first proposed by Elsworth & Lee for sands to almost all soil types. This was possible after appropriate modification of Elsworth and Lee's original method.

Determination of Hydraulic Conductivity Using a Modified Cylindrical-Half-Spherical Piezocone Model

“…To improve the accuracy of the model, Chai et al [6] proposed a half-spherical flow approach (hereafter described as Chai's method), as shown in Fig. 1.…”

“…Hydraulic conductivity may influence consolidation deformation [4][5][6], the design of pit dewatering [7], the estimation of foundation settlement, and the analysis of soil consolidation [8][9][10][11][12]. Therefore, numerous researchers have been dedicated to studying methods of hydraulic conductivity measurement [13][14][15][16][17][18][19][20][21][22][23][24][25].…”

“…The second refers to an indirect way to introduce a relation for the coefficient of consolidation of soils via the dissipation test [26][27][28][29], which is time-consuming and labour-intensive. The third involves a semi-theoretical method based on dislocation analysis, Darcy's law, and cavity expansion theory [6,[21][22][23][24][25]. Elsworth and Lee [21,22] first proposed an explicit equation on the basis of a spherical flow assumption.…”

“…Elsworth and Lee [21,22] first proposed an explicit equation on the basis of a spherical flow assumption. Subsequently, Chai et al [6] modified the method using a half-spherical flow assumption, which can be used for normally or lightly overconsolidated clayey deposits and loose sandy deposits. Zou et al [25] proposed an explicit equation with radial flow normal to an improved cylindrical surface.…”

DISCUSSION: Estimating hydraulic conductivity from piezocone soundings. J. C. CHAI, P. M. A. AGUNG, T. HINO, Y. IGAYA and J. P. CARTER (2011). Géotechnique 61, No. 8, 699–708, http:dx.doi.org/10.1680/geot.10.P.009

“…Vessia, Istituto di Ricerca per la Protezione Idrogeologica, Bari, Italy, F. Casini, ETH, Zurich, Switzerland and S. M. Springman, ETH, Zurich, Switzerland Piezocone (uCPT) measurements were applied to estimate horizontal field hydraulic conductivity k h , representing radial dissipation of pore pressures induced by advancing a penetrometer into lightly overconsolidated clayey soil (Chai et al, 2011). The authors calculate the dimensionless hydraulic conductivity K D (¼ f (ó 9 vo k), equation (1)) based on hemispherical cavity expansion and an isotropic hydraulic conductivity k, using vertical hydraulic conductivity k ¼ k v from oedometer tests.…”