Elasto-plastic constitutive law

By applying the procedure described in Sect. 2.10.3, the elasto-plastic constitutive law is obtained, which relates the increment of effective stress da to the strain increment lie as 

6 aassical Theory of Consolidation for Saturated Porous Media 

Since both the original and modified Cam clay models employ an associated flow rule, the plastic potential function g is the same as the yield function /. We use (6.88) and (6.98), and obtain the hardening coefficient h as follows  

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Abstract Chalk is the constituent material of numerous oil reservoirs in North Sea. The mechanical behaviour of a saturated chalk has been largely studied. However, different aspects of its behaviour are not yet well understood material characteristics depend on the saturating fluids and chalk response is time-dependent. This paper proposes the PASACHALK numerical model an elasto-plastic constitutive law is presented, which reproduces the different plastic mechanisms of the chalk (pore collapse and shear failure) and the influence of pore fluids. The water sensitivity of this soft rock is explained by the existence of suction effects in chalk. Finally, a simulation of a hypothetical reservoir is proposed to show the response of the elasto-plastic model during depletion phase and water injection phase. 

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