Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Journal of Theoretical and Applied Mechanics

2 2022

Powiadomienia systemowe

Sesja wygasła!

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Study on mechanical characteristics of rock type I fracture and anchorage strengthening mechanism

Zhang Wei, Zhao Tongbin, Guo Weiyao, Xing Minglu

Journal of Theoretical and Applied Mechanics

2022

Vol. 60 nr 3

423--434

Engineering rocks are easily affected by excavation unloading and are in uniaxial compres- sion or tension, forming a typical I-type tension crack. Anchor rods are often used for on-site support to ensure safety and reliability of the project. The study of propagation and pen- etration of type I tension cracks and quantitative evaluation of rock anchoring effects are of great significance for exploring mechanical properties of rock fracture and revealing the mechanism of rock failure. In this paper, combined with speckle light measurement, a rock fracture toughness test of different anchoring positions and pre-tightening forces is carried out, the deformation evolution law of the crack tip and the fracture mechanics characteris- tics of the anchored rock are obtained, and the anchoring strengthening mechanism of the rock is discussed based on the theory of the net stress intensity factor. The research shows that the rock fracture process is divided into four stages: elastic deformation, steady crack propagation, crack instability propagation and residual deformation. After anchoring, the time of crack instability growth can be prolonged by 172% and the final residual deformation can be increased by 148%. Compared with the unanchored rock, the fracture toughness of rock initiation and instability increased by 83% and 124% respectively, and increased with growth of the pre-tightening force, which shows that the bolt increases the critical value of rock initiation and instability to achieve the toughening effect. After the rock is anchored, the time required for the crack to propagate to the same length increases by 55%, and the lateral deformation area is reduced by 46%, indicating that the lateral closing force of the bolt inhibits crack propagation and delays the instability of the rock matrix.

Prefabricated fractured rock under stepwise loading and unloading

Zhang Wei, Zhao Tongbin, Yin Yanchun

Journal of Theoretical and Applied Mechanics

2022

Vol. 60 nr 1

167--179

After the engineering rock mass has been affected by comprehensive effects of mining and disturbance, it experiences an input of external energy as well as dissipation and release of internal energy. From the viewpoint of energy, characteristics of rock failure are studied, and the law of rock unstable deformation and energy evolution is analyzed. The damage mechanism of rock is revealed easily. A gradual loading and unloading test of fractured rock is carried out to analyze deformation characteristics of the fractured rock during the load- -bearing process, and to study the law of energy dissipation and release under different load- ing and unloading stress levels. The results show that: (1) the load-bearing time, loading and unloading stress level, stress at crack initiation and peak stress of fractured rock gradually decrease with an increase in the number of cracks, and the descending speed decreases grad- ually with the increase in the number of cracks; (2) the strain at crack initiation and peak strain of the fractured rock increase gradually with an increase in the number of cracks, and the gathering speed decreases with the increase of the number of cracks; (3) the released strain energy and dissipation energy of fractured rock increase with an increase of loading and unloading stress levels, and the increasing rate gradually slows down; (4) the number of acoustic emission events is positively related to the degree of rock damage, and the increase in the number of cracks will prolong duration of the number of acoustic emission events. The results have a theoretical value for energy evolution and deformation damage of fractured rock masses, and also provide experimental experience to study the instability precursor information of rock materials from the viewpoint of energy.