Failure of VERT Wall System: Forensic Evaluation and Lessons Learned

VERT Wall Systems (VWS) is a proprietary construction process developed, designed, and constructed by Geo-Con to support excavations. The VWS is a top-down, in-situ gravity wall system, which primarily uses deep soil-mixing method (DMM) technology. The DMM technology involves in-situ mixing of existing weak soil with cementitious materials like lime, cement, or combination of both. There are no standard designs available for the VWS; as such, the size, strength, and spacing of the components are site specific. In this study, the reported movement into the VWS system constructed in Irving-Las Colinas area in Texas was evaluated. Visual assessment of the problems indicated failure of a substantial body of soil at the site. The movement involved the failure of VWS retaining wall. Evaluation of the VWS design was checked using finite element program PLAXIS and limit equilibrium program GSTABL. The general trend between the soil movement measured by inclinometers and the wall movement predicted by FEM appeared to be in reasonable agreement with each other. The evaluation also elucidated some salient issues concerning the application of the VWS at this site and the reasonableness of the design assumptions used. This engineering evaluation also demonstrated that testing coupled with experience and engineering judgment should be used to provide design parameters and should be the basis of the VWS design assumptions.