## 4 Conclusions  
A pseudo-static test combination with abutment, steel H-pile and soil was carried out to study the mechanical behavior of the soil-abutment-pile system under reciprocating low-cycle displacement load. The testing results were discussed and explored, including earth pressure behind abutment, hysteretic and skeleton curves, horizontal deformation of specimen and rotation of abutment. The typical observations and conclusions are described as follows.  
1. The passive earth pressure of backfill is over 30 times of active earth pressure, and the passive earth pressure coefficient is larger than those by others ([PERSON], [PERSON], NCHRP, [PERSON], England, Massachusetts, Rankine theory, Coulomb theory and JTG D60-2015) due to the ratcheting effect of soil. The existing calculation method earth pressure of backfill behind abutment is not accurate for that of IAJB.
2. The earth pressure behind abutment has a typical triangular distribution when the horizontal displacement is small (less than 8 mm), and it shows a trapezoid distribution when the soil is close to abutment under a large horizontal displacement (larger than 8 mm). The earth pressure at horizontal distances of 0.6\(H\) and 1.4\(H\) from the back of the abutment is triangular under different displacements. The pile has little influence on the distribution of earth pressure when distance exceeds 1.4\(H\).
3. The accumulative deformation is observed and the hysteretic curves are dramatically asymmetrical, but the soil-abutment-pile system shows a linear behavior yet.
4. The energy dissipation capacity when test specimen moves to the positive direction is much larger than that when specimen moves to the negative direction. The soil-abutment-pile system in IAJB has favorable energy dissipation capacity and seismic behavior. The sum of horizontal deformation of abutment-pile-soil specimen are far larger than that of traditional pile-soil specimen due to the effect of accumulative deformation. Its maximum horizontal deformation occurs at the pile body rather than the pile head. The phenomenon of void is observed at the surface of the backfill and the interface between abutment and pile, which is also one of the reasons for bumping at bridge-end and settlement of soil.
5. The time-history horizontal accumulative deformation goes up with the increase of displacement load, and the growth rate becomes faster when the displacement load reaches 10 mm. The accumulative deformation is relatively small for the abutment, but it is large in the buried depth of 1.0\(b\)-3.0\(b\) for pile. The traditional calculated theory of deformation of pile is not appropriate to calculate the accumulative deformation. The noncumulative deformation is nearly the same  
Figure 25: Angle diagram. (**a**) Positive direction. (**b**) Negative direction.  
as the deformation of traditional theory. The influence of accumulative deformation should be considered in practical engineering.
6. A significant difference of inclinations in the positive and negative directions increases when the displacement load is relatively large. The rotation of abutment when bridge expands is larger than that when bridge contracts.  
All authors substantially contributed to this work. [PERSON] designed and fabricated the pile model. [PERSON] and [PERSON] designed the experiment. [PERSON] and [PERSON] performed the experiments and analysis. [PERSON] and [PERSON] wrote the paper. [PERSON] and [PERSON] revised and finalized the paper. All authors helped with the writing of the paper. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China with Grant Numbers 51578161, and by the Fuzhou Technology Bureau with Grant Number 2018-G-63.  
The authors declare no conflict of interest.