Study On The Interaction Mechanism Between Cantilever Pile And Embedded Rock Mass Under Large Excavation

Recently, the land resources are becoming more and more scarece, especially in the mountainous city. In those cities, the geological disasters such as landslide body excavated usually in order to fit the urban development, because those cities have more mountain and less land, and their space are narrow, and those area often happen serious geological disasters. And when the geological disasters body such as landslide have been excavated, the anti-slide pile designing by ordinary design method could not be able to work again. So, it is necessary to research the interaction mechanism under the great excavation of rock in front of pile.With the excavation of the rock, the interaction between pile and rock has significant difference when the rock slope has different height and width. This paper, using a slope in YueYang, HuNan as a instance, widely collecting data, researched the interaction between pile and rock by means of indoor physical experiments and numerical simulation. The following conclusion has been obtained:1. The theoretical research about interaction mechanism between pile and rock. In this paper, the form of the possible destruction of rock mass are studied, the ideal failure mode of rock with small rock width and large rock width is obtained. the formula of plastic zone height with small rock width and large rock width is deduced. And plastic zone height is calculate by using practical engineering parameter. the numerical simulation results and theoretical results were compared.2. The physical experiment research about failure modes and deforming characteristics of rock mass. Comparing those test results under different pile width of rock and different rock mechanic parameters, the variation laws of strain and displacement of rock in front of pile are obtained with the force changing under different rock width, and the variation laws with rock width and height changing under same force are also obtained. The conclusion shows:1) The displacements of each of measuring point on rock decrease with the width of the rock increasing. The displacements of free face rock changing with the thrust is consistent with the rock uplift displacement changing with the thrust. except the displacements’value have slightly difference. When the rock width is small, the rock displacement parabolic increases with thrust increasing at first, and then slowing down, then rapid increasing. When the rock width is great, the rock displacement parabolic increases with thrust increasing.2) The strain and the increasing rate of strain both soar up with the thrust increasing. rock mass between piles with the increase slowly with thrust increasing, when the thrust size increase to a certain value, the increasing rate increases rapidly, and exceed strain increasing rate of s the rock mass in front of pile. The strain of rock mass ahead pile and rock mass between piles slightly decrease with the rock width increasing.3) With the rock width increasing, the stretching capability of rock is enhanced, and the failure mode become from tensile fracture to uplift failure. Under the pile group effect, the connected fractures are easy to appear in the area between two piles.3. The numerical simulation research about interaction between pile and rock and failure mode of rock mass under large excavation interaction. This paper build those numerical models which have different force, different rock width, different height, different slope angle, different rock-socketed depth. Through calculating those models, the variation laws of rock stress, rock displacement, pile displacement can be obtained. Besides, the curve of that pile lateral stress changing with depth under different rock width and height also can be obtained. And the curve is compared with theoretical calculation results. The conclusion shows:1) Rock that stays in front of pile remain a rise with the increase of its width, but it remains a steady until up to the maximum value. Meanwhile, the width of rock will also increase and then decrease until keep steady when it is up to the minimum value. Its displacement and rate of displacement increase with the decrease of its width. However, this value also increases with the rise of its height and landslide thrust. Compared the impact of its height, the width of rock has a huge influence on stress and this means that the influence of its height on displacement at top of pile decrease with the rise of its width.2) Displacement at top of pile increases with displacement at front of pile and this looks like parabola. This means that it raises a value and then the curve will slow. The stress at side of pile decreases with the decrease of its width. Its distribution form is from triangle distribution when the width of rock is large to parabola distribution when its width becomes small.3) The slope angle of pile at the front of rock slope is more big, the change degree of rock displacements before pile and the displacements of pile top are more intense along with the change of rock width. The change of slope angle does not affect the variation laws of rock displacement and the displacement of top pile, but great affect the displacement value. With the increase of slope angle, and rock width increasing make the capability of piles against sliding of rock mass more better.4) the rock-socketed depth increase with the decrease of stress, strain at front of pile and displacement the top of pile, but this change remains a slow, which means that stress, strain at front of pile and displacement at the top of pile stay a slowly rise with the height of rock. In short, there is a good impact for rock-socketed depth.In summary, The mechanism of interaction of pile and rock with huge excavation at front of pile is presented, and factors of effect of against sliding of rock are studied. This can provide a guidance for engineering.