## 3 Experimental Results and Analyses
### Earth Pressure behind Abutment
#### 3.1.2 Distribution of Earth Pressure  
Since the active earth pressure is quite low compared to the passive earth pressure in Figure 9, the distribution of active earth pressure will not be discussed further in this paper. Figure 11 shows the distribution of passive earth pressure along the height of abutment when the abutment moves to the positive direction. Figure 11a shows the distribution of earth pressure for sensors T1-T4 and T17 at the back face of the abutment. Besides, Figure 11b-d show the distribution of earth pressures for sensors T5-T8, T9-T12 and T13-T16 at horizontal distances of 0.2\(H\), 0.6\(H\) and 1.4\(H\) (0.2 m, 0.6 m and 1.4 m) from the back of the abutment, respectively.  
It is observed that the earth pressure behind abutment has a typical triangular distribution when the horizontal displacement is small (less than 8 mm) in Figure 11a,b, or when the soil is far away from abutment (larger than 0.6\(H\)) in Figure 11c,d. However, the earth pressure shows a trapezoid distribution when the soil is close to abutment under a large horizontal displacement (larger than 8 mm), as shown in Figure 11a,b. The reason of forming a trapezoid distribution is that the horizontal movement of the bottom of integral abutment is influenced by the constraint of steel H-pile when abutment is under the large displacement load, which reduces the horizontal deformation of the abutment and thus reduces the earth pressure. This trapezoid distribution is also consistent with the results of [PERSON] [33]. In Figure 11c,d, 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, which indicates that the pile has little influence on the distribution of earth pressure when the soil is far away from the abutment.  
Figure 10: Relationship between \(\Delta\)/\(H\) and \(K_{p}\).  
Figure 12 shows the distribution of earth pressure along the longitudinal direction when abutment moves to the positive direction under different displacement steps. For brevity, results from four typical earth pressure cells (T3, T7, T11 and T15) are discussed in this section. In Figure 12, it is observed that the earth pressure decreases with the increases of the horizontal distance. The decreasing trend is similar to an exponential decay. Within the distance of 0\(H\) to 0.6\(H\), the earth pressure drops significantly, especially under large displacement loads. Within the distance of 0.6\(H\) to 1.4\(H\), the rate of reduction in earth pressure slows down. Finally, the earth pressure reduces to the earth pressure at rest under different displacement steps, which means the displacement loads have little influence on earth pressure when the horizontal distance is larger than 1.4\(H\). This also illustrates that the soil box was sufficiently large that can be neglected the boundary effect on the development of earth pressure.  
Figure 11: Distribution of passive earth pressure along the height of abutment. (**a**) Cells at the back face of the abutment. (**b**) Cells at horizontal distance of 0.2\(H\). (**c**) Cells at horizontal distance of 0.6\(H\). (**d**) Cells at horizontal distance of 1.4\(H\).