Performance of low-order triangular elements during plastic flow

An important characteristic of many soil models is a volume change during p lastic flow. In computations, this plastic volume change is expressed via a kinematic constraint on the possible deformations. Due to this constraint the plane-strain three-noded triangular element exhibits locking when plast ic deformations occur, under dilatant, contractant and isochoric conditions . It is demonstrated that using the method of enhanced assumed strains by S imol this locking cannot be remedied. Far six-noded wedges and four-noded a nd five-noded pyramids the same conclusion is obtained.