sigmaP | R Documentation |
A function to determine the preconsolidation stress (σ_P). It is a parameter obtained from
the soil compression curve and has been used as an indicator of soil load-bearing capacity as well as to
characterize the impacts suffered by the use of machines.
The function sigmaP()
contains implementations of the main methods for determining the pre-consolidation
stress, such as the Casagrande method, the method of Pacheco Silva, the regression methods and the method of the
virgin compression line intercept.
sigmaP(voidratio, stress, n4VCL = 3, method = c("casagrande", "VCLzero", "reg1", "reg2", "reg3", "reg4", "pacheco"), mcp = NULL, graph = TRUE, ...)
voidratio |
a numeric vector containing void ratio (or bulk density) values. |
stress |
a numeric vector containing the applied stress sequence. |
n4VCL |
the number of points for calculating the slope of the soil Virgin Compression Line (VCL), which is obtained by linear regression. |
method |
a character indicating which method is to be computed; one of the following:
|
mcp |
the maximum curvature point in log10 scale of |
graph |
logical; if TRUE (default) the compression curve is plotted. |
... |
further graphical arguments. |
casagrande
is the method proposed by Casagrande (1936). The preconsolidation stress obtained via VCLzero
corresponds
to the intersection of the soil Virgin Compression Line (VCL) with the x-axis at zero applied stress, as described by
Arvidsson & Keller (2004). reg1
, reg2
, reg3
and reg4
are regression methods that obtain the preconsolidation
stress value as the intercept of the VCL and a regression line fitted with the first two, three, four and five points of the curve, respectively,
as described by Dias Junior & Pierce (1995). pacheco
is the method of Pacheco Silva (ABNT, 1990).
You may follow the flowchart below to understand the determination of the preconsolidation stress through sigmaP()
.
A list of
sigmaP |
the preconsolidation stress. |
method |
the method used as argument. |
mcp |
the maximum curvature point in log10 scale of |
CI |
the compression index. |
SI |
the swelling index. |
Anderson Rodrigo da Silva <anderson.agro@hotmail.com>
ABNT - Associacao Brasileira de Normas Tecnicas. (1990). Ensaio de adensamento unidimensional: NBR 12007. Rio de Janeiro. 13p.
Arvidsson, J.; Keller, T. (2004). Soil precompression stress I. A survey of Swedish arable soils. Soil & Tillage Research, 77:85-95.
Bowles, J. A. (1986). Engineering Properties of Soils and their Measurements, 3rd edition. McGraw-Hill Book Company, Inc. NY, 218pp.
Casagrande, A. (1936). The determination of the pre-consolidation load and its practical significance. In: Proceedings of the International Conference on Soil Mech. and Found. Eng. (ICSMFE), Cambridge, MA, 22-26 June 1936, vol. 3. Harvard University, Cambridge, MA, USA, pp. 60-64.
Dias Junior, M. S.; Pierce, F. J. (1995). A simple procedure for estimating preconsolidation pressure from soil compression curves. Soil Technology, 8:139-151.
voidratio
, maxcurv
, fitlbc
pres <- c(1, 12.5, 25, 50, 100, 200, 400, 800, 1600) VR <- c(0.846, 0.829, 0.820, 0.802, 0.767, 0.717, 0.660, 0.595, 0.532) plot(VR ~ log10(pres), type = "b") # find the 'mcp' sigmaP(VR, pres, method = "casagrande", mcp = 1.6, n4VCL = 2) # fitting the VCL sigmaP(VR, pres, method = "casagrande", mcp = 1.6, n4VCL = 3) # self-calculation of "mcp" argument for Casagrande method sigmaP(VR, pres, method = "casagrande", n4VCL = 3) # Pacheco method sigmaP(VR, pres, method = "pacheco") # Regression method sigmaP(VR, pres, method = "reg3") # End (not run)
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.