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Tunnel Boring Machine Crushed Limestone as a Cement Grout
The recent advances in the construction of tunnels and subways in urban cities involve the use of tunnel boring machines (TBM). The use of TBM in Riyadh, Saudi Arabia, resulted in huge quantities of crushed limestone powder (≈3 million cubic meters) and generally treated as waste. This work is aimed at utilizing the fine portion of the crushed limestone (powder) as a cement grout material and its possible use in shotcrete and lining of the tunnel works. The suggested mixture can be an efficient replacement for the sand cement grouts or lean concrete used in tunnel lining. This material is expected to be cost-effective and environmentally friendly as less cement and sand need to be used. The proposed mixture was subjected to geotechnical and material characterization as usually conducted for materials of similar applications. Mixtures of cement:powder of ratios 1:1, 1:1.2, and 1:1.4 were examined at a water-cement ratio of 0.6. Curing was carried out for 7, 14, and 28 days. Compressive strength tests were performed, and stress-strain relationships were established at early curing times and full-strength development to determine the crack initiation development as a key driven factor of a tunnel collapse. The results were compared to sand cement grout to measure performance improvement. The modes of failure and shear zones developed during tests were studied. Moreover, the impact of the crushed powder content on the strength and stress-strain relationship was evaluated. Characterization of the material, including particle size and shape description of the selected powder, was determined, and aggregate quality and durability tests were evaluated. The strength improvement due to the introduction of this material is attributed to the interlocking nature of the angular shape of particles. The workability of the mixture can be improved using additives of plasticizers, and this will enable using less water-cement ratio. More studies and examinations are suggested on the composition and gradation of the crushed limestone powder obtained from the tunnel-boring machine.
Tunnel Boring Machine Crushed Limestone as a Cement Grout
The recent advances in the construction of tunnels and subways in urban cities involve the use of tunnel boring machines (TBM). The use of TBM in Riyadh, Saudi Arabia, resulted in huge quantities of crushed limestone powder (≈3 million cubic meters) and generally treated as waste. This work is aimed at utilizing the fine portion of the crushed limestone (powder) as a cement grout material and its possible use in shotcrete and lining of the tunnel works. The suggested mixture can be an efficient replacement for the sand cement grouts or lean concrete used in tunnel lining. This material is expected to be cost-effective and environmentally friendly as less cement and sand need to be used. The proposed mixture was subjected to geotechnical and material characterization as usually conducted for materials of similar applications. Mixtures of cement:powder of ratios 1:1, 1:1.2, and 1:1.4 were examined at a water-cement ratio of 0.6. Curing was carried out for 7, 14, and 28 days. Compressive strength tests were performed, and stress-strain relationships were established at early curing times and full-strength development to determine the crack initiation development as a key driven factor of a tunnel collapse. The results were compared to sand cement grout to measure performance improvement. The modes of failure and shear zones developed during tests were studied. Moreover, the impact of the crushed powder content on the strength and stress-strain relationship was evaluated. Characterization of the material, including particle size and shape description of the selected powder, was determined, and aggregate quality and durability tests were evaluated. The strength improvement due to the introduction of this material is attributed to the interlocking nature of the angular shape of particles. The workability of the mixture can be improved using additives of plasticizers, and this will enable using less water-cement ratio. More studies and examinations are suggested on the composition and gradation of the crushed limestone powder obtained from the tunnel-boring machine.
Tunnel Boring Machine Crushed Limestone as a Cement Grout
Alokili, Turki (author) / Dafalla, Muawia (author) / Al-Mahbashi, Ahmed (author) / Alnuaim, Ahmed (author) / Mutaz, Eljunaid (author)
Geo-Congress 2023 ; 2023 ; Los Angeles, California
Geo-Congress 2023 ; 45-54
2023-03-23
Conference paper
Electronic Resource
English
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