Application of Diverse Ground Improvement Techniques for the Stabilization of Reinforced Earth Wall Approach Ramps

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Abstract: As part of the Kingdom of Saudi Arabia’ s pre-eminent destination, an Elevated Iconic Steel structure supporting a section envisaged to be built connecting to lower-level area. The structure has length of 635m, and it projects 60 to 70m above existing ground levels and is supported by multiple columns. The approach ramps towards the structure connects the piled abutments on both sides are proposed via a Reinforced Earth Wall with heights from 3m to 26m. The soil conditions comprising of silty sands and gravels in the top layers were shown to be of collapse potential by inundation due to water ingress., as evident from tests carried out in accordance with the BREA Infiltration test and Plate Load Tests, PLT as per Saudi Building Code SBC 303:2018. Therefore, treatment was required to mitigate such issues and ground improvement was determined to provide an increase in the stiffness and shear strength of the ground to be able to withstand overburden loads and limit post construction settlements on the surface to mitigate the potential of any total and differential settlement issues and ensure smooth traffic flow and transition between structure and approach ramps. The Ground improvement specifications allowed for various measures to the consultant’ s satisfaction including a deep soil mixing technique in the areas where under the maximum heights of the reinforced earth walls. In these areas a specified stiffness and average target unconfined compressive strength, UCS of 1.5 MPa corresponding to a minimum ground stiffness of 200 MPa are specified. In the areas where relatively lower heights of reinforced earth walls are located, a combination of vibro-replacement-stone columns supplemented by further surface compaction techniques using Rapid Impact Compaction, RIC, and High Energy Impact Compaction, HEIC are applied. Quality assurance testing consisting of Wet Grab Sampling, Zone Load Tests, ZLT and Cone Penetration Tests, CPT were carried out for verification of ground improvement.

Keywords: Approach Ramp, Reinforced Earth Walls, Soil Mixing, Unconfined Compressive Strength, UCS

Mr. VIJAYA BHUSHAN RAO Rao Parigela; Mr. Jason Douglas Redgers

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