The Research And Application Of Fracture Mechanics In Slope Stability Analysis

The slope stability has been more attentioned in the fields of civil engineering.The continuum mechanics has been widely used in the slope stability analysis. Butthese methods can not take the influence of internal defects into consideration. Theresearch object of fracture mechanics is the structure with macro crack. The slope isjust the cracked structure. Thus the principles of fracture mechanics can be applied tothe analysis of slope stability. This article mainly focused on the analysis of slopestability in two different failure modes.Assuming that the destruction of ordinary homogeneous clay slope is caused bythe cracking in the slope crest. The slope stability is judged on whether the cracklength in the slope crest has reached the critical value. The main contents andconclusions are as follows:①Determine the most vulnerable cracking position according to the stressintensity factor distribution curve of the slope crest by using the finite elementsoftware. Then determine the critical crack length.Set a crack in the most easilycracking position.While the crack is longer than the critical crack length, it will crackaccording to the calculated crack propagation angle in turn untill the crack crackinterconnected. The fracture surface got is the most dangerous sliding surface based onfracture mechanics. According to the ratio of stress intensity factor of typeⅠand typeⅡ during the crack propagation, determine that the type of slope failure is mixedⅠ-Ⅱ, but it is closer to type Ⅰ.②Comparing the most dangerous sliding surface based on fracture mechanicswith the sliding surface based on the traditional limit equilibrium method, we can getthat it is feasible to study the stability of clay slope through the principle of fracturemechanics.③Apply the finite element software to studying the effects of slope height andslope angle on the slope fracture failure. The most easily cracking position increaseswhen the height or angle of the slope increases. The critical crack length decreaseswhen the height or angle of the slope increases. The slope failure is closer to type Ⅰfracture when the height or the angle of slope increases.For the slope containing collinear cracks internally or formed by layered rock, the internal defects are reduced to a set of collinear cracks inside. Assuming that the slopefailure is caused by the expansion of this group of internal collinear cracks. Criterionof slope stability is whether the equivalent stress intensity factors of crack tip is lessthan fracture toughness or not. The main contents and conclusions are as follows:①W hen the slope has flawed crack inside, the sliding-resistance force of rock-soilmass in the position of cracks is negligible. Using finite element software, byassuming collinear cracks of different lengths and line spacing, get the correspondingstress intensity factor. Then research the change rule of the stress intensity factor ofcrack tip when the crack number, crack length and crack spacing is different.②Comparing the equivalent safety factor based on fracture mechanics and thesafety factor based on limit equilibrium method demonstrates,we can get that theequivalent safety factor of slope based on the fracture mechanics is feasible.③Comparing the two fracturing failure modes,the difference and connectionbetween two failure modes are researched.