## 3 Test Results  
### Earth Pressure  
As pile components were pushed in, pressure shifted, highest at 12 m and lowest at 4 m. Post hammering, the pressure dropped, stabilizing in 2 h. Values of 4 and 8 m normalized in 24 h, 12 and 16 m stayed raised around 20 kPa. Figure 4 describes the entire process of earth pressure change. During the drilling operation, the radial earth pressure on the borehole wall steadily increases with depth, and each part of the drill rod has a varied effect on the soil pressure. During the planting of the pile, there is not much change in earth pressure because the diameter of the prefabricated pile is small. After grouting, the cemented soil moves upward, dissipating most of the extrusion force. At a radial distance of 3.5 m, the soil pressure change is most significant at 8 m during the drilling process, increasing by 50 kPa. During the withdrawal of the drill, the soil pressure also increases, but the increment is small, about 15 kPa. During the planting of the pile, the earth pressure changes at each point are less than 5 kPa. Overall, during the PGP pile installation process, it is important to consider the  
Figure 3: Sensors installation and monitoring. (**a**) Install the piezometer; (**b**) Install earth pressure cell; (**c**) Inclinometer measuring; (**d**) Noise monitoring; (**e**) Vibration accelerometer installation; and (**f**) The PGP pile construction.  
influence of soil pressure on the surrounding soil during the drilling process and to pay close attention to the diameter of the prefabricated pile and the flowability of cemented soil after grouting to reduce the impact of extrusion force on the surrounding soil.  
Figure 4: Comparisons of earth pressure. (**a**) A-TY before and after construction; (**b**) A-TY construction process; (**c**) B-TY1 Stage 1; (**d**) B-TY1 Stage 2; (**e**) B-TY3 Stage 1; and (**f**) B-TY3 Stage 2.  
Earth pressure increases during initial pile construction due to pile penetration within 1/3 \(L\). Soil extrusion mainly affects pile tip plane, influencing a 3 m range above and below. Above this, frictional force from pile shaft dominates over the tip's extrusion. Shallow soil has a smaller, quicker pressure rise and recovery than deep soil. Pressure from the pile machine weight recovers when removed, but construction-induced pressure can persist in deep layers for more than 2 days. It can be seen that the maximum earth pressure increment generated by PGP piles and driven piles is different at different depths, and the methods of generation are also different: driven piles are due to the driving of the pile body, while PGP piles are caused by agitation due to the rotation of the drill pipe.  
Overall, at the same distance during construction, the earth pressure increment generated at different depths by the PGP pile is like the driven pile. At a depth of 4 m, the PGP pile generates greater earth pressure due to the larger mass of the pile-planting machine, which also affects the shallow soil. Since the measured earth pressure is not an instantaneous value during construction but the residual earth pressure after compression, the PGP pile exerts a more sustained pressure on the soil during construction.