Pull-Out Resistance of Rebar Stake Depending on Installation Conditions and Compaction Levels of Agricultural Soil

Abstract

Strong winds, particularly in the absence of disaster-resistant designs, significantly impact the stability of greenhouse foundations and eventually lead to structural damage and potential harm to crops. As a countermeasure, rebar stakes are commonly used to reinforce the foundations of non-disaster-resistant greenhouses. This study evaluates the pull-out resistance (Rpull-out) of rebar stakes considering various factors like soil compaction, embedded length, installation duration and angle, and changes in soil water content against uplift pressure by strong winds. A combination of field (i.e., the cone penetration test and rebar stake pull-out test) and laboratory (i.e., the compaction test, soil compaction meter test, and soil box test) tests are performed for the assessment of Rpull-out. The results indicate that Rpull-out increases with higher soil compaction, greater embedded length, longer installation duration, and an inclined installation angle. The soil compaction exerts the most significant impact; 90% to 100% of the soil compaction rate has approximately 10 folds higher Rpull-out than the 60–70% compaction rate. If the embedded length is increased from 20 cm to 40 cm, there is a two-fold increase in the average of Rpull-out. Inclined installation of rebar stakes increases Rpull-out by 250% to 350% compared to vertical installation, and rebar stakes installed prior to the uplift event have 1.5 to 6.4 fold increases in Rpull-out than those with instant installation. Additionally, we observed variations in the surface soil moisture due to climatic changes introducing variability in Rpull-out. These findings lead to the proposition of efficient rebar stake installation methods, contributing to the enhanced stability of a greenhouse.