Meshing problems

Hi all,

I'm working in a Plaxis 3D model for an underground excavation. Geometry is quite complex due to geology and excavation phases so intersections generate some little triangles that are giving me problems with mesh generation. I've tried with different options (coarseness) for mesh generator but I haven't succeeded. Model is reporting errors due to small edges as follows:

!!!!> _mesh 0.025 256 True 0.5 0.002 0.5
Meshing failed with the following error:
Fatal: Could not generate mesh.
Warning: 1 EMR warning has been detected.
Warning: # 1/1 of small edges: detected size 3.37e-02; this is 1.62e+01 times smaller than minimum targeted element size. Related geometries: Polygon_5_13, Polygon_7_9. Inspect the geometry locally.

!!!!> _mesh 0.025 256 True 0.5 0.002 0.05
Meshing failed with the following error:
Fatal: Could not generate mesh.
Warning: 1 EMR warning has been detected.
Warning: # 1/1 of small edges: detected size 3.37e-02; this is 1.62e+01 times smaller than minimum targeted element size. Related geometries: Polygon_5_13, Polygon_7_9. Inspect the geometry locally.

Can anyone give some advice to solve this kind of issues? 

Thanks in advance,

Francesc