Experimental Study On Soil Pressure Behind The Semi-integral Abutment Considering Seasonal Temperature Effect

Semi-integral abutment jointless bridge will play a very important role in the construction of new bridges of medium and small span or seamless transformation of old bridges because of its unique advantages,and has a wide application prospect.However,there is no mature understanding and unified calculation method of the soil pressure behind the abutment due to the semi-integral abutment-soil interaction.Therefore,it is of great significance to study the interaction mechanism between the abutment and soil of semi-integral bridge.The main research work and conclusions of this paper are as follows:Through quasi-static test of semi-integral abutment model specimens under horizontal loading,the mechanism of semi-integral abutment-soil interaction is studied.The numerical value and distribution of earth pressure behind semi-integral abutment and the variation of hysteretic skeleton curve and rotation angle of abutment are discussed by analyzing the test data.The test results show that: 1)The hysteresis curves are "semi-shuttle" in the whole cycle(3 years),but the plumpness decreases year by year.The hysteresis circles migrate periodically with seasonal temperature changes.2)Under the effect of seasonal temperature,the earth pressure behind the abutment has a large cumulative effect,and the skeleton curves of three years are approximately parabolic.3)During the whole period(three years),the change of the rotation angle between the top and bottom of abutment is basically the same,and its value is related to the magnitude of loading displacement,and the trend is increasing year by year.According to the time history of the rotation angle of abutment,under the same loading displacement,with the increase of loading times,the turning angle of abutment also increases step by step.4)Under the action of temperature cyclic load,because of the difference of the distance between the soil behind the semi-integral abutment and the abutment back,the distribution law of earth pressure is also slightly different,and it shows "trapezoidal" or triangular distribution;With theincrease of displacement load,the value of earth pressure behind the abutment increases and reaches the limit of passive earth pressure,resulting in Ratching phenomenon;Under the same loading displacement,the action force in the second and third years,the maximum annual increase is 624.48 kPa.Based on the analysis of the test results,the test values are compared with the existing theoretical calculations and specifications,and it is found that: 1)When the abutment displacement is greater than 4 mm,the test value is much larger than the calculation value of the earth pressure behind the abutment and the related theoretical calculation value in the existing codes for seamless bridges.2)Based on the Massachusetts calculation method,the earth pressure coefficient behind the semi-integral abutment is modified.3)It is found that the earth pressure behind the abutment shows a two time function type(a year and a half)and an exponential type(one and a half years)attenuation rule in the three year period according to the relation of the distance which is between the soil behind the abutment and the abutment back and the value of earth pressure behind the abutment.