Experimental study results of the effectiveness of underpinning a strip foundation fragment using a drill-and-injection enlarged pile

The article presents the results of static load tests of a strip foundation fragment (bearing plate) underpinned by a drill-and-injection pile with enlarged base. The static load tests were carried out in the summer of 2020 at the testing site in the city of Tyumen. A drill-and-injection pile with enlarged base is an injection pipe that has a rubber membrane-glass at its lower end. With the help of a hydraulic packer, the solution is injected into the rubber membrane-glass. After the solution has hardened, an enlarged base of the injection pipe of the required size is formed. To assess the results obtained, static load tests are also carried out both for a strip foundation fragment not underpinned using a drill-and-injection pile with enlarged base and a separately located drill-and-injection pile with enlarged base. Based on the data obtained during static load tests in the course of the experimental study, the following dependency graphs are formed: the graph of the settlement of a strip foundation fragment without underpinning and with underpinning by means of an enlarged pile depending on the pressure under its base; and the graph of the settlement of an enlarged drill-and-injection pile depending on a static pressed load. The results indicate that the use of an enlarged drill-and-injection pile to underpin a strip foundation fragment allows increasing the safe working pressure under the strip foundation fragment base by an average of 25% and reducing its settlement by an average of 43 %.