Journal of Engineering Geology, Vol.6, No.2, Autumn 2012 & Winter 2013
Constitutive modeling of cemented gravely sands including the effects of cement type

*A. Hamidi, P. Yarbakhti:
School of Engineering, KharazmiUniversity

Received: 26 Aprill 2011 Revised 25 Oct 2011
Abstract
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In this paper, a constitutive model is proposed for prediction of the shear behavior of a gravely sand cemented with different cement types. The model is based on combining stress-strain behavior of uncemented soil and cemented bonds using deformation consistency and energy equilibrium equations. Cement content and cement type are considered in a model as two main parameters. Based on the proposed method, the behavior of cemented soil with different cement types is predicted for conventional triaxial test condition. Porepressure developed during undrained loading besides volumetric strains in drained condition are also modeled according to this framework. Comparison of model results with experimental data indicates its reasonable accuracy.

KeyWords: Constitutive model, Cemented soil, Gravely sand, Stress-strain behavior, Cement Content, Cement type.

*Corresponding author [email protected]

Introduction
Slopes and vertical cuts are usually observed to be stable for a long time in coarse-grained alluviums. Stability is often attributed to the cementation effects producing increased shear strength in these deposits. Due to the problems associated with preparation of undisturbed samples from these soils, cementation effects are usually studied using artificial cementation. Experimental studies on behavior of cemented sands have been reported by several researchers like Clough et al. (1981), Leroueil and Vaughan (1990), Coop and Atkinson (1993), Ismail et al. (2002) and Consoli et al. (2006).
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Downloaded from jeg.khu.ac.ir at 11:37 IRST on Saturday October 28th 2017

Many researchers have worked on constitutive modeling of the behavior of cemented sands, e.g. Pekau and Gocevski (1989), Reddy and Saxena (1992), Lagioia and Nova (1995), Vatsala et al. (2001), Vaunat and Gens (2004). In the present study, a constitutive model is developed for cemented gravely sand of Tehran alluvium. Figure 1 shows gradation curve and Table 1 indicates physical properties of the representative soil. Model results are compared with three different sets of experimental data to investigate its ability. Data include triaxial tests conducted by Asghari et al. (2003), Hamidi et al. (2004) and Haeri et al. (2005). Stress-strain behavior in drained and undrained conditions besides pore pressure and volumetric strains are modeled and results showed good consistency for propose model.

Fundamentals of model
Vaunat and Gens (2004) and Gens et al. (2007) separated the shear behavior of an argillaceous rock into individual behaviors of uncemented soil and cemented bonds. They used deformation consistency between two parts to model the mechanical behavior of an argillaceous rock by following equations:
1268732149348

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Downloaded from jeg.khu.ac.ir at 11:37 IRST on Saturday October 28th 2017

p  (1)pm (pb ) (1) q  (1)qm (qb ) (2) where pm and qm are the mean and deviatoric effective stresses for uncemented soil matrix. Also pb and qb are the corresponding values for cemented bonds. Parameter  is a coefficient which controls the contribution of each component in mean effective stress (p) and deviatoric stress (q) of cemented soil. It can be determined using the following equation:
0eL (3)
where 0 is the initial value of  when there is no damage to the bonds and can be determined by model calibration. Value of damage parameter, L, can be determined using the following equation:
kb0  (4)
L Ln kb 

Where kb0 is the stiffness of cemented bonds in zero confining stress and kb is its value in other confinements.
This framework is used as the basis of model in present study. The stress-strain behavior of the uncemented gravely sand is predicted using generalized plasticity model proposed by Pastor et al. (1985).
Also a new model is suggested for the behavior of cemented bonds. These two parts are combined to determine stress-strain behavior of cemented soil.

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قیمت: تومان

دسته بندی : زمین شناسی

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