The complex fluid-solid interactions and irregular crack patterns in hydraulic fracturing cause substantial numerical challenges, which can make conventional crack modeling methods ineffective. In the present work, a stabilized and nodally integrated meshfree formulation for hydro-mechanical modeling of crack propagation in saturated porous media is developed. Under the stabilized conforming nodal integration framework , a fluid pressure projection method  is employed to achieve a stable equal-order reproducing kernel approximation for the mixed poromechanical formulation. Furthermore, a damage particle method is proposed, which approximates the fractures by a set of damaged particles under the meshfree discretization. For each damaged particle, a continuum damage mechanics model is adopted as a smeared type description of the equivalent crack segment at the nodal position, and a dissipation energy-based scaling law is naturally introduced to enforce the bulk energy dissipated over the nodal quadrature cell to be consistent with the surface fracture energy of the equivalent crack segment. A simple tracking procedure for damaged particles is employed to prevent spurious damage initiation and spread, and thus the global energy dissipation is conserved. In addition, the influence of cracking on the fluid flow is captured by adopting a cubic law-based anisotropic permeability model, which is updated during the simulation by extracting the equivalent crack opening displacement from the damage and deformation field. The proposed reproducing kernel damage particle method provides an effective means in modeling fluid-driven propagating cracks. Several numerical examples are given to demonstrate the effectiveness of the developed meshfree formulation.
 Chen, J. S., Wu, C. T., Yoon, S., & You, Y. (2001). A stabilized conforming nodal integration for Galerkin mesh-free methods. International journal for numerical methods in engineering, 50(2), 435-466.
 Wei, H., Chen, J. S., & Hillman, M. (2016). A stabilized nodally integrated meshfree formulation for fully coupled hydro-mechanical analysis of fluid-saturated porous media. Computers & Fluids, 141, 105-115.
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