Research In The Regularity Of Bored Pile By The Osmosis Of Cement Paste And Its Impact On Loading

During the construction of the bored pile, the phenomenon that the cement paste permeate in the earth around the pile is apparent and this phenomenon will influence the pile-soil boundary. The most of current numerical simulation haven't involved the osmosis impact to the pile-soil boundary. This method ignores the actual load-bearing mechanism and makes the calculation is not accurate enough. Although some research has been conducted both at home and abroad, it hasn't yet formed a complete theory system, nor has a clear interpretation about the variation law of the osmosis under the influence of different factors. According to engineering experience, in this experiment we chose the filling height, water cement ratio and the initial aperture as the test influencing factor to explore the osmosis law. At first, I confirm the existence of the osmosis of cement paste, then give the value range and strength of osmosis body, to provide the basis for parameter selection which of models in calculation.Through the following four aspects that pore water pressure, pile diameter changes, strength of osmosis body and hardness, I research the variation law under the different influencing factor. At first, I confirm the existence of the osmosis of cement paste based on the rise of pore water pressure and pile diameter, and I defined the osmosis body to be considered in the finite element calculations under what conditions according to the strength and hardness of osmosis body. Secondly, based on the analysis of the pore water pressure of different locations in both directions, we can get the variation laws of pore water pressure value along the pile shaft radial and tangential; according to the analysis of the pile diameter increase of the 9 set of orthogonal experiment data, we can get water cement ratio and filling height had the greatest influence on pile diameter change; through the chemical composition analysis of osmosis body, we can get the variation law of infiltration intensity under different factors and the result shows the water cement ratio is the significant factors; by micro vickers hardness testing method, we can get the water cement ratio had the greatest influence on osmosis body hardness drop. The above research provide basis for selecting parameter in calculation of the pile foundation ultimate load. At last, through the calculation of digging pile ultimate load by strength reduction method and load increment method, I confirm the necessity and feasibility of the method that considering the osmosis body in calculation of pile foundation ultimate load.