Field Preliminary Test of Air Jet Boosting Combined with Vacuum Preloading Drainage Technology

The vacuum preloading method for treating coastal soft clay faces issues such as low drainage efficiency and drainage board clogging. This is urgent to research and improvement of conventional vacuum preloading drainage technology. Improve the traditional booster pipe into a pipe with multiple Laval circular jet nozzles, forming an air jet combined with vacuum preloading drainage system. Preliminary tests were conducted on site during the final stage of vacuum preloading, comparing the changes in drainage volume before and after air injection, and analyzing the effects of different air injection depths and durations. The results shows that the improved "convergent-expansion-straight" circular nozzle based on Laval nozzle configuration demonstrates superior air acceleration performance and outlet impact force. After ventilating the field air jet boosting pipe, the vacuum drainage efficiency in the final stage of vacuum preloading can be increased by 5%~15%, proving that the pressurization in the form of high-speed air jet has an effective promoting effect on vacuum preloading drainage. However, during the initial on-site testing process, it was also discovered that this technology requires strict control over the duration and volume of gas injection to avoid adverse effects such as reduced vacuum drainage efficiency and gas leakage along the pipe wall. The proposed solutions include "small gas volume, pulse type" jets, sealed pipe bodies, which can be used as a reference for subsequent improvements and engineering application.