# Lateral Pressure of Poured Concrete: Arguments from Ultra-Deep Diaphragm Wall (120 m) Construction
## 3 Results
The lateral pressure at each measurement point reaches its maximum lateral pressure in approximately 1.5 hours above the hydrostatic pressure. During this process, the concrete in the vicinity of the measurement point gradually sets, and the cohesion is no longer affected by the new round of pouring. With time, the degree of setting increases, and the fluidity of the concrete decreases, so the lateral pressure increment appears negative. If the interval between two casts is short, there is also be a slightly positive value of the lateral pressure increment. Figure 4: Development of lateral pressure during the filling process (partial enlarged view). (**a**) The depth of the measurement point is 100 m; (**b**) the depth of the measurement point is 80 m; (**c**) the depth of the measurement point is 40 m.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**No. **} & \multirow{2}{*}{**Start Time**} & \multirow{2}{*}{**End Time**} & \multirow{2}{*}{**Casting Time (min)**} & \multicolumn{3}{c}{**Lateral Pressure Increments at Each Point (kPa)**} \\ \cline{5-6}  & & & & \(-\)**100 m** & \(-\)**80 m** & \(-\)**40 m  
As shown in Figure 5a, the lateral pressure remains at roughly 1.325 MPa, i.e., the slurry hydrostatic pressure value, until the fourth cast. The fourth to seventh castings cause a rapid increase in the lateral pressure value, especially the fifth casting, followed by a gradual hardening of the concrete during the casting interval and a decrease in the lateral pressure value. The lateral pressure increases by 3.25 MPa, and the rise time lasts for 2 h. The lateral pressure stops increasing and gradually decreases from the after the eights cast. As shown in Figure 5b, the lateral pressure value increased significantly from the sixth to the ninth cast and decreased slightly during the interval between casts, with the increase time lasting for 2.5 h and lateral pressure increase of 0.4 MPa. After the ninth cast, the lateral pressure did not show a significant increasing trend and leveled off. The trend shown in Figure 5c is similar to that depicted the first two graphs, and the 14 th to 17 th casts all caused a change in lateral pressure, with a particularly obvious increase in the 15 th cast. The lateral pressure decreased significantly after the 17 th cast. Although the 18 th and 19 th casts caused a slight increase in lateral pressure, a decreasing trend still occurred at the end of the casting process. Figure 5 shows that all four casts before reaching the peak caused an increase in lateral pressure, which subsequently decreased due to hardening. The increase in lateral pressure at different heights lasted for about 2.5 h, whereas a decrease occurred rapidly for the next 0.5 h, after which the lateral pressure plateaued. The height corresponding to each cast can be calculated based on the volume of concrete loaded in each mixer truck and the area of the slot. If the height required for each measurement point from the beginning of the change in lateral pressure to the peak is defined as the characteristic height, the characteristic height can be calculated as approximately 21 m.  
As shown in Figure 6, the lateral pressures at each of the three measured points were measured after the lateral pressure exceeded the respective hydrostatic pressure. Interestingly, the most prominent points all occurred at a relative template height of about 21 m; therefore, this was defined as the characteristic height. The lateral pressure tends to increase above the characteristic height and decrease almost linearly below this height. The main reason for the decrease in lateral pressure is the gradual hardening of the concrete, which limits its flowability. Figure 5: Effect of the number of casts on lateral pressure at depths of 100 m, 80 m and 40 m. (**a**) The depth of the measurement point is 100 m; the red dots indicate the casting period (fourth to ninth cars), and the blue dots indicate the period between casts.