Experimental Study of Crack Propagation in Cracked Concrete

Siyao Wang,Shaowei Hu

doi:10.3390/en12203854

Abstract

The intersection of cracks has an important role in the key technology of hydraulic fracturing for enhancing the recovery of tight hydrocarbon reservoirs. On the basis of digital image correlation technology, three-point bending tests of concrete beams with an edge crack and a central preset crack were conducted to investigate the propagation of cracks after intersection in concretes. Concrete beams with cracks of different positions, lengths, and approach angles were tested, and results were analyzed. In conclusion, the crack positions, crack lengths, and approach angles significantly influence the crack propagation in naturally cracked concrete. A large distance between the crack tip and central point at the preset transverse crack and crack length indicate a high possibility of the edge crack vertically crossing the preset crack. In particular, the crack restarts from the preset crack tip after intersection when the distance between two cracks is smaller than 30 mm and when the preset crack length is smaller than 40 mm. A large approach angle corresponds to a large carrying capacity of the beam and a high possibility of the crack propagating perpendicularly. An improved criterion of restart cracking after interaction is proposed, and the restart points of all tested beams are predicted and compared with the experimental results. A good agreement is observed, which proves that this criterion is reliable.

Highlights

Hydraulic fracturing is a key technology for enhancing the recovery of tight hydrocarbon reservoirs in petroleum industries [1,2,3]
Crack propagation experiments in cracked concrete beams were presented in this work
The crack interaction behavior was directly observed by using the Digital image correlation (DIC) technology

Summary

Introduction

Hydraulic fracturing is a key technology for enhancing the recovery of tight hydrocarbon reservoirs in petroleum industries [1,2,3]. Numerous natural fractures exist in shale formations, and these pre-existing natural fractures have an important role in the hydraulic fracturing process because they can influence the process and path of hydraulic fracture propagation. Natural fractures affect the propagation of hydraulic fractures, and the passage of internal driving forces of hydraulic fractures can be greatly influenced by multiple natural fractures. The interaction of cracks in rock-like materials, such as concrete, should be investigated. The propagation criterion of crack interaction can guide the study of complex fracture propagation. A series of criterions were proposed to predict single crack propagation in rock-like materials

Methods

Findings

Discussion

Conclusion