# Model Test Study on a Shield Tunnel Adjacent to Pile in the Sub-Clay of a Coastal Area
## 4 Test Results
### Surface Deformation
When the grouting filling coefficient was 1.5, according to the analysis of the influence of pile and grouting on surface settlement in Figure 18, the grouting settlement was reduced by 77.4% compared with the no-grouting case, and the maximum settlement with pile was reduced by 19.7%, on average, compared to the no-pile case; The control effect of grouting on surface settlement was remarkable: settlement steps were generated around the pile, the loss of soil mass on the side of the pile near the tunnel was reduced effectively, and the retaining effect was obvious. The solid black straight line in Figure 18 indicates the position of the pile, which indicates the relative relationship between the ground settlement and the position of the pile. Figure 16: Surface displacement with different grouting filling coefficient. Figure 17: Relationship between pile displacement and grouting. The maximum sedimentation values measured by dial gauge for the 33 sets of orthogonal tests are shown in Table 7. The reduction ratio of the maximum surface settlement of different pile positions relative to the no-pile case is shown in Figure 14:0  
The tests showed that grouting has obvious control effects on surface subsidence, and the control degree of maximum surface settlement varies greatly with the different pile positions. The appropriate control range was \(1D\)-\(2D\). The surface settlement could not be well controlled if the transverse spacing between piles and tunnels was too large or too small. When the pile bottom level was below the tunnel arch waist, the control effects of ground settlement was significantly enhanced, so the driving of isolation piles should be located within the range of \(1D\)-\(2D\) of the tunnel, and the best effect should be achieved by further extending the pile bottom below the inverted arch. Figure 14:1 Influence of pile and grouting on the surface subsidence. According to the settlement data obtained under the various working conditions, the settlement curve was fitted to obtain the reverse bending point distance \(i\). The linear function correction method was used to solve the settlement tank correction parameter \(k\) of Peck curve. The formula for fitting the relationship between \(K\) value and coverage-span ratio of no-piles was as follows. Table 9 shows the \(K\) value under the various working conditions with piles. Figure 14:2  
The test showed that the main influence indicators of \(K\) value include coverage-span ratio, soil properties, construction methods, etc. The \(K\) value range of clay was obtained from 0.4 to 0.6 [12]. The \(K\) value range of sandy soil was obtained from 0.25 to 0.45 by [13]. The \(K\) value range of station construction obtained by [14] the \"PBA\" drift-pile method from 0.61 to 0.82, and the \(K\) value range of the center drift excavation method was from 0.40 to 0.65 according to the specific project. The important influencing factor of \(K\) value obtained in this test was the coverage-span ratio. Based on the data of various working conditions, the recommended reference range of \(K\) value of settlement trough according to the width correction parameter can be given as:  
\[\left\{ \begin{array}{l}H/D<0.5;\;1.1<K<1.2\\ 0.5<H/D<1;\;1.0<K<1.1\\ 1<H/D<2;\;0.4<K<0.8\\ 2<H/D<3;\;0.5<K<0.75\\ H/D>3;\;K<0.5\end{array} \right. \tag{10}\]  
The \(K\) value decreased with the increase in coverage span ratio. The \(K\) value of surrounding rock with piles decreased by 0.075, on average, compared with the no-piles case. The \(K\) value increased with the increase in pile-tunnel distance and decreased with the increase in pile burial depth.