Calculation method for earth pressure behind integral abutment under horizontal reciprocating large displacement

To analyze the effect of horizontal reciprocating large displacement generated by the abutment on the interaction between the abutment and the backfill behind the abutment under the actions of strong earthquake and temperature, a quasi-static test for the interaction among the integral abutment, H-shaped steel pile, and soil was carried out. On the basis of the test results, the distribution law of the earth pressure behind the integral abutment under the action of large displacement was studied. According to the distribution of the earth pressure behind the abutment, the relational expression between the action point location of the resultant earth pressure behind the abutment and the loading displacement was proposed, and an improved calculation method for the earth pressure behind the integral abutment was given based on the existing research. Research results indicate that when the abutment is loaded in the positive direction (the abutment squeezes the soil behind the abutment), the earth pressure behind the abutment first increases and then decreases as the loading displacement rises. Earth pressures at the abutment back and 20% of the abutment height behind the abutment are highly affected by the abutment displacement and has a trapezoidal distribution along the depth direction. In the earth pressure distribution at the abutment back, due to the constraint of H-shaped steel pile at the bottom of the abutment, the maximum earth pressure is located at a depth of 0.875 m, and the earth pressure at the bottom of the abutment decreases slightly. Earth pressures at 60% of the abutment height and 1.4 times the abutment height behind the abutment are less affected by the abutment displacement and is triangularly distributed along the depth direction. When the abutment is loaded in the negative direction (the abutment deviates from the soil behind the abutment), the earth pressure behind the abutment is triangularly distributed along the depth direction, and the earth pressure behind the abutment has no connection with the loading displacement, and its value can be neglected relative to the positive loading. Under the action of a horizontal reciprocating large displacement, the soil behind the integral abutment will face a void phenomenon, and the void range will exceed 37.5% of the abutment height. The earth pressure behind the abutment reduces exponentially along the longitudinal direction, and it reduces faster than that under the action of a small displacement. The action point location of the resultant earth pressure behind the abutment decreases gradually as the loading displacement increases, and the earth pressure coefficient behind the abutment has an obvious nonlinear relationship with the loading displacement, which is reflected by the law of first increasing and then decreasing. Existing earth pressure calculation methods do not take into account the effect of the abutment displacement or consider that the earth pressure behind the abutment rises with the increase in the abutment displacement when small displacements occur and remains basically unchanged when large displacements occur. The determination coefficient of the proposed earth pressure fitting formula is 0.92, and the relative error between the calculated value and the test value is 6.2%, which can be a useful supplement to the existing earth pressure calculation methods.