At-rest lateral earth pressure in compacted silica sand

ABSTRACT

At-rest lateral earth pressure is one of the major sources of disturbing force on retaining structures and provides resisting force for anchors and piles. A theoretical model is proposed, and experimentally validated, for the normally and overconsolidated at-rest lateral earth pressure coefficients in silica sand. In addition, the experiment illustrates a procedure to determine the maximum historic vertical stress equivalent to the standard and modified Proctor energies of compaction. The previous equivalent maximum historic vertical stress, which is found to be constant for the relative density reached by each energy of compaction, is then proposed as a parameter to determine the overconsolidation ratio within the backfill and its resultant at-rest lateral earth pressure distribution behind a vertical wall. The at-rest lateral earth pressure distribution incorporated with the overconsolidation ratio naturally results in a greater magnitude and is curved in contrast to the linear distribution characteristic of a normally consolidated state. A limit equilibrium analysis and a plane-strain particle-scale model of a granular media under critical state were used to derive the equations herein.

KEYWORDS:

• At-rest lateral earth pressure coefficient
• cohesionless soil
• compacted soil
• critical-state friction
• experimental investigation
• overconsolidation ratio
• particle-scale behaviour
• plane-strain
• silica sand

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request, specifically data for Figures 7–10 and Tables 4– 8.

Notation

The following symbols are used in this paper:	=
Dr	=	relative density (%);
K0	=	at-rest coefficient of lateral earth pressure of normally consolidated cohesionless soil;
K0-OC	=	at-rest coefficient of lateral earth pressure in overconsolidated and compacted deposits;
nc	=	critical porosity (i.e. porosity of the soil deposit);
nc,r	=	relative critical porosity;
OCR	=	overconsolidation ratio;
α	=	auxiliary angle defined in the herein particle-scale model of a heap standing at-rest;
β	=	static angle of repose;
γ	=	unit weight of soil;
κ	=	slope of unload-reload consolidation line in ln scale;
Λ	=	plastic volumetric strain ratio (1 - κ/λ);
λ	=	slope of primary consolidation line in ln scale;
σ’h	=	lateral or horizontal effective stress;
σv’0	=	current vertical effective stress;
σv’max	=	equivalent maximum historic vertical consolidation stress or preconsolidation pressure;
Ø’c	=	angle of grain crushing;
Ø’cv,ps	=	internal available plane-strain constant-volume friction angle;
Ø’ cv,ps,OCR	=	Ø’cv,ps equivalent to a given overconsolidated state;
Ø’cs,ps	=	external or boundary developed plane-strain critical-state friction angle;
Ø’cs,ps,OCR	=	Ø’cs,ps equivalent to a given overconsolidated state;
Ø’p,ps	=	plane-strain friction angle from pushing or rearrangement; and,
Ø’μ	=	interparticle sliding friction angle.

Additional information

Funding

Financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) and Concordia University is gratefully acknowledged.