Development and application of portable tilt tester for basic friction angle of rock joint

As a fundamental parameter for estimating the shear strength of rock joints, the basic friction angle is typically obtained via tilt tests. Given the prevalent issue of low precision in existing tilt testers suitable for field operations, a novel tilt testers for measuring the basic friction angle of rock joints has been developed, which features field operability, automatic data logging, and remote information interaction capabilities. Real-time warnings regarding operational compliance enable precise control over the slow tilting process of specimens. Dynamic monitoring throughout the entire test and accurate capture of critical values allow for the precise acquisition of the basic friction angle. Real-time data transmission between on-site devices and remote servers facilitates bidirectional information interaction between indoor and outdoor locations. Preliminary application of the developed tilt tester was conducted, and the results demonstrate that: wear on the specimen surface and powder accumulation will alter the physical properties of the friction interface and thus exert a significant impact on the test results; The basic friction angles obtained from the three-core test and the block test are relatively close, with the latter yielding test data with lower discreteness; with moisture content as the variable, the test results of unsaturated specimens exhibit larger values and higher discreteness. This research provides technical support for the development of related testers and subsequent experimental studies.