Frictional behaviour of segmental retaining wall units infilled with recycled concrete aggregate
The use of segmental retaining wall units as the facing column for mechanically stabilized earth (MSE) retaining walls has increased noticeably all over the world. Hollow and solid, both types of modular block units are used in dry-stacked facing columns. Nowadays, Hollow concrete units are being implicated frequently because of its cost-effectiveness and other technical advantages. The cavities of hollow concrete units are filled with natural (fresh) aggregates for better shear resistance. The use of fresh aggregates as in-fillers in retaining wall constructions is expensive and unsustainable (annihilation of natural resources). This study mainly focuses on frictional behavior of newly designed and manufactured precast “I” blocks infilled with fresh and recycled aggregates. A series of tests were performed using a specially designed & fabricated direct shear apparatus to assess the frictional behavior of infilled blocks under different normal loading conditions. The tests were executed based on the exiting ASTM and National Concrete Masonry Association (NCMA) test protocols. Test results were outlined in the form of shear stress-displacement relationship to compare the effect of recycled aggregate against the fresh aggregate. Shear capacity envelopes were also plotted using Mohr-Coulomb failure criteria to find out the angle of friction for each case. Test results revealed that the angle of friction of the blocks infilled with the recycled aggregate is almost equal to those with the fresh aggregate.
Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines
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Long term strength and safety in steep soil slopes reinforced by polymer materials
Abstract A rational method is described for the selection of material properties and design safety factors for steep reinforced slopes. The proposed method clearly separates the forces required for equilibrium, which depend on soil mechanics, and the forces made available by the inclusion of reinforcement layers. Accepted limit state concepts in geotechnical engineering are adopted for the calculation of the required forces for design. For the calculation of the available forces, emphasis is first placed on the importance of the design time and the design temperature for the polymer reinforcement. Secondly a distinction is made between the reference properties of the material supplied by the manufacturer and the expected properties of the reinforcement in the ground, at the end of the design life, when it has been subject to mechanical damage and the soil environment. The need for extrapolation of data to determine the long-term properties is the third main theme. The focus is on the calculation of the allowable force in the reinforcement available to maintain equilibrium. The latest data on polymer reinforcement materials are examined in the paper. The number and position of the required safety margins for the proposed method are described, and magnitudes for them are suggested wherever possible, based on existing knowledge.