Response of Cracks to Construction Vibrations and Environmental Effects

Abstract

This paper summarizes micro-inch response of cosmetic cracks in a typical slab-ongrade ranch style house to both construction equipment-induced vibration and environmental (weather) effects. This structure was instrumented, and its response studied as part of the development of an Autonomous Crack Measurement (ACM) system. ACM systems are intended to record-with a single sensor-micro-inch crack displacements from both long-term environmental changes and transient construction vibrations for comparison in an understandable fashion. Ground motions were measured with velocity transducers, and micro-inch crack displacements were measured with LVDT displacement sensors. Construction within 14 m (45 ft) of the house involved trackhoe excavation for a 10x12 ft. reinforced concrete box culvert , chain trencher excavation for an 8-inch water service line, and vibratory compaction of trench backfill and granular sub-grade. As with many other studies of this nature, it was found that the weather induced crack response far exceeded that produced by construction vibrations even when produced by vibratory rolling within 3 m (10 ft) of the structure.

Pore-water pressure accumulation during closely spaced earthquakes: Fundão Tailings Dam

“…Using the measured peak particle velocities from these blasts, the ground acceleration was estimated for each blast and are shown in Table 1. The measured peak particle velocities were converted to acceleration using equation (11-3) from Dowding (1996), which is: where R is the distance from the blast to the dam, i.e. 2600 m, c is the propagation velocity, i.e.…”

“…2600 m, c is the propagation velocity, i.e. 400 m/s, which correspondes to weathered bedrock, W is the blasting charge weight per delay, which was estimated from the measured magnitude of the blasts (3.3 and 3.5, see Table 1) to be 2200 kg TNT based on USGS (2008), is the density of the bedrock, which was assumed to be 2.24 g/cm, which was derived from 22 kN/m 3 /9.81 m/s 2 , so it has little impact on the results (Dowding 1996).…”