The red mud has a huge stock and high increase

which brings serious problems such as safety

environmental protection and land occupation. To expand red mud resource utilization and advance green composite foundation technology

we propose a red mud–fly ash geopolymer (RFG) pile technology. This study evaluated the material preparation

construction method

pile quality

vertical bearing characteristics

and environmental impact of the RFG pile

based on laboratory tests

an in-situ pile installation test

and a static load test on a silty-clay foundation. The results show that: 1) RFG piles can be formed by pumping and underwater casting using conventional wet drilling. When the mass ratio of red mud: fly ash: medium sand: gravel: blast furnace slag powder is 1:2:2:4.94:0.1

with a liquid-solid ratio of 0.55

the RFG mixture exhibits good workability suitable for pumping and underwater pouring. The slump can be controlled in 220−225 mm

and the strength can reach 13.9 MPa after 28 days of curing at room temperature. 2) RFG piles exhibit strong compressive bearing performance. For a single RFG pile 10 m long and 0.52 m in diameter

the vertical ultimate bearing capacity is 753 kN; the bearing capacity of a single-pile composite foundation with a spacing of 3 diameters is 240 kPa. 3) On-site formation quality of the RFG pile is good

and core samples collected along the pile length are largely intact. The coring rate of the six piles is more than 99%

and the compressive strength of the core samples at different depths is more than 10 MPa

up to 19.5 MPa. 4) The implementation of RFG piles has no adverse impact on the quality of surrounding water bodies and has not changed the evaluation results of groundwater corrosivity. The research results lay a foundation for the engineering application of RFG pile

and also provide a new idea for improving the utilization rate of red mud