Computer Vision Observation for Progressive Failure Characteristics of a Moderately Weathered Red Mudstone Foundation: Design and Experiment

Abstract

The bearing stratum of high-rise and ultra-high-rise buildings in southwest China has inevitably faced moderately weathered red mudstone. It was a waste of the potential bearing stratum calculated according to the specification, as the bearing stratum obtained from laboratory and in situ tests was much higher than the values suggested by the specification. Rock mass surface deformation detection is of great significance in the safety management of a foundation project. Some correlation between surface deformation and failure characteristics may exist that could help to understand the bearing stratum of the moderately weathered red mudstone. This research was conducted to study the progressive failure characteristics of the moderately weathered red mudstone through surface deformation. In situ load, triaxial, and binocular visual technology were employed for data acquisition. The proposed conjecture was illustrated and verified by a group of experiments from three construction sites. Five stages could be described as the progressive failure of the moderately weathered red mudstone: compaction, elasticity, elastoplasticity, plasticity, and failure. Furthermore, the surface displacement increment fluctuates with the loading time and fades into the distance. Therefore, this research could provide a robust, practical application for analyzing the progressive failure of moderately weathered red mudstone.

Experimental study on the punching failure model of soft red rock subgrade by BPT-BVM methods and it’s assessment of the load bearing capacity

“…The confining pressure range of this research is preliminarily determined according to the actual excavation depth, and the upper load of the foundation. The strength of the sample in field was low 13 . So, the confining pressure is characterized by 6 gradients: 0.3 MPa, 0.6 MPa, 0.9 MPa, 1.2 MPa, 1.5 MPa and 1.8 MPa, respectively (parallel experiments a and b under pressure in each group were conducted) 13 .…”

“…The strength of the sample in field was low 13 . So, the confining pressure is characterized by 6 gradients: 0.3 MPa, 0.6 MPa, 0.9 MPa, 1.2 MPa, 1.5 MPa and 1.8 MPa, respectively (parallel experiments a and b under pressure in each group were conducted) 13 . For the rock mass test, a loading rate of 0.05 MPa/s was applied to the machine, and synchronously apply confining pressure and axial pressure at pre-set values of the disturbance.…”

“…The reason is that failure mechanism of mudstone foundation cannot really be reflected by compressive strength testing, which results in the poor bearing capacity adequacy based on the reduction in rock compressive strength and poor agreement with load test results. The theory can not truly reflect the load-bearing failure mechanism of mudstone foundations, and practice lacks experimental demonstration based on load testing and direct rock strain testing, which severely underestimates the load-bearing capacity of soft rock 1 , 4 , 13 , 21 , 27 . In practice, Zeng et al 28 , Peng 29 , Liu et al 30 have been gradually modifying the standards based on the load test of rock foundation, point load test, pressuremeter test, etc.…”

“…2 ). The whole-rock sample was not crushed 13 . Combined with the stress molar circle and the resistance envelope of the mudstone at the site (Fig.…”

“…Depending on the monitoring range, the rock mass deformation area is divided into six layers, and the spacing of each layer is approximately 20 to 30 mm. The displacement increment of each ring layer is defined as the average displacement of all markers in the same ring layer and the cumulative displacement increment is the cumulative displacement increment of the same ring layer with loading time 13 . The first to sixth layers gradually moved away from the bearing plate.…”