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This work aims to analyze the behavior of a new post-grouted micropile setup developed in tropical soil. Its main innovation is the use of high mechanical resistance steel pipes (N80 class) for drilling and as a structural component of the micropiles. The pipes have special manchette valves uniformly spaced to allow neat cement grout injection into the soil. Two instrumented micropiles with 0.3 m diameter (after injection) and lengths of 19.4 m and 21 m were installed at Experimental Site III of the University of Campinas (Unicamp). The geological profile of this site presents a sandy clay surface layer (porous and collapsible) followed by a layer of sandy silt (diabase residual soil). The piles were subjected to compressive slow maintained loading tests and were instrumented along their depth with strain gages. No geotechnical failure was observed during the load test. The maximum load achieved by the MC1 and MC2 micropiles were 2.210 kN and 2.470 kN, respectively. The load test data were extrapolated to estimate the ultimate geotechnical pile capacity. The extrapolated geotechnical failure load was above 2.500 kN for both micropiles and similar to those estimated by the Federal Highway Administration FHWA (2005) load capacity method. It was verified that (1) the pile material undergoes creep under stress above 25 MPa on the transversal section of the pile and (2) the debonding effect during the loading process. The micropiles showed higher values of skin friction compared with other piles installed in the same geological-geotechnical context (tropical soil).

The use of micropiles has been increasing in recent years, mostly for horizontally loaded cases. Given the little information about this foundation type under lateral top-loading, especially in high-porosity and collapsible soils, a total of four transversal loading tests were carried out in a new post-grouted micropile configuration with length of 17 m and diameter of 0.3 m, two in natural soil moisture conditions and two in flooded conditions. Load-displacement curves and the horizontal reaction coefficient of the new micropile were obtained. Results were compared with other pile types laterally tested under the same conditions and in the same geological and geotechnical contexts. Generally, results were better than the other pile types, mainly under saturated condition. The new micropile proved to be a better and more efficient alternative for local lateritic soil treatment when compared with the soil-cement treatment.

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