Experimental Study On Bearing Characteristics Of Uplift Pile With Overlying Soil

According to the static load test in the field,the comparison and analysis of the bearing characteristics of the pile with the enlarged base rock-socketed piles,the variable-cut rock-socketed piles and the equal-cut rock-socketed piles are finished preliminarily.Using the centrifuge model test of the uplift pile,the rock-soil body failure modes of the rock-socketed piles with the enlarged base and the rock-socketed rock piles with equal-cut were analyzed.It is found that the bonding strength of pile-soil interface has significant influence on the bearing and breaking characteristics of the rock-socketed piles.Finally,by using the numerical simulation,the bearing characteristics of the variable-cut rock-socketed pile and the equal-cut rock-socketed pile are further compared.The quantitative analysis of the effect of pile-soil interfacial bonding strength on the failure characteristics of the equal-cut piles embedded in strong weathered sandstone is completed.The main conclusions are as follows:(1)In the field test of the variable-cut rock-socketed piles,the pile diameter changes from 1.0m to 0.6m in rock strata,the uplift resistance provided by rock strata is variable-cut pile / equal-cut pile =0.71.Combined with numerical analysis,it is found that the pile diameter changes to an hour in the stratum,and the uplift force provided by the stratum decreases with the same extent as the variation of pile diameter.Combined with numerical analysis,it is found that the uplift force provided by the stratum decreases with the same extent as the variation of pile diameter.(2)According to the field test,under the same conditions,the enlarged base pile can significantly increase the ultimate pullout load and can effectively reduce the displacement compared to the equal section pile.The uplift force provided by the enlarged base is 3.3 times that of the rock socketed pile with equal section.(3)In the model test,it is found that the failure modes of the rock-soil body with equal-cut rock-socketed piles are divided into cylindrical type(pull-out type)and composite type.When the bond strength between pile and rock mass is very strong,the failure mode is composite.On the other hand,it is cylindrical.For the rock-socketed piles,the failure form is trumpet type.Combined with numerical simulation,it is found that for the equal-cut piles in strong weathered sandstone,when the bond strength of pile-soil interface' strength reduction factor at a lower time(the size no more than 0.3),There is a larger possibility of cylindrical type;with the increasing with the strength reduction factor,The failure mode changes from the cylindrical type to the trumpet type.(4)Under the ultimate load,the lateral friction resistance distribution of equal-cut piles and piles with the enlarged base presents different form.For the equal-cut piles,when the uplift load gradually approaches the ultimate load,the peak value of the frictional resistance on the side of the pile occurs within 1m after the uplift pile enters the rock formation,for the piles with enlarged base,the peak generally appears at the base.(5)Convert model test piles to prototype piles.Under the conditions of the same pile diameter and rock-socket depth,the ultimate pull-out load of piles with enlarged base about 2 times,1.8-2.3 times,and 1.2-1.4 times to the equal-cut piles corresponding pile diameter of 0.6m,1.0m and 1.5m respectively.