# Settlement Prediction and Differential Settlement Criterion for Heightening and Thickening Leveee
## 3 Case Study
### Case Introduction
#### 3.1.4 Installation Process of Internal Settlement Observation  
The leveling observation and internal settlement observation methods used in this study are shown in Figure 9. The specific installation process of the internal settlement observation was as follows:  
1. The single end anchor head was installed at the deepest position;
2. The both ends anchor head was installed at the middle position. The differences between single end anchor head and both ends anchor head is the number of pipelines. The single end anchor head has no pipeline outlet, so it was installed at the deepest position;
3. The third step was to connect the pedestal and displacement sensor. The most important consideration in this step is the corresponding relationship between the serial number of displacement sensors and the position of the anchor head, as the displacement sensor and the anchor head will be buried in the HTL;
4. The fourth step was to assemble the pedestal. In this step, all displacement sensors were installed in the pedestal. The pedestal is the only instrument that will be outside the levee;
5. The fifth step was to assemble all anchor heads using a hydraulic pipe and plastic pipe. The aim of the hydraulic pipe was to transport hydraulic oil. The aim of the plastic pipe was to make every anchor head reach the right depth;
6. The sixth step was to inflate the oil hydraulic pump (pressure approximately 3-4 MPa) using hydraulic oil. After that, the all instruments can be placed into the hole;
7. The paws of all anchor heads were reduced. The aim of inflating the oil hydraulic pump was to shrink the paws of all anchor heads;
8. A hole was drilled on the spot;
9. All instruments were transported to the spot. Transportation in this step required several people because the instruments are very long;
10. All instruments were placed into the hole. The hydraulic pipe was to be cut off so that the paws of all anchor heads would be stuck into the hole wall;
11. Installation was completed.
12. The data collection is shown in Figure 9b.  
Figure 8: Measuring points layout for HTL.  
The main reasons for the different settlement rules of the HTL are as follow: 1. The soils of different HTL sections are different; 2. The additional stress of different sections is different; 3. The environmental factors of different sections are different (for example, some sections may produce frost heavy deformation). In particular, the S-shaped settlement-time curve from Section II is due to seepage deformation.  
For Section I, the settlement stabilization time is approximately 100 days. In fact, monitoring data show that the settlement stabilization time is approximately 150 days. Moreover, the settlement stabilization times of the GSPM and hyperbolic models are close to the measured results. In terms of the final settlement prediction, the prediction results of the three models were basically consistent with the measured results. Hence, when the logistic model describes the hyperbolic settlement-time curve, it will result in an error of settlement stabilization time.  
For Section II, the hyperbolic model is not convergent, which shows that the hyperbolic model is not suitable for predicting the S-shaped settlement-time curve. However, the predicted results of the GSPM and logistic models were basically consistent, which shows the validity of the GSPM in predicting the S-shaped settlement-time curve.  
From the above analysis, the GSPM is effective and stable in predicting the hyperbolic and S-shaped settlement-time curves.  
Table 6 presents the error analysis for different sections. The bold words in Table 6 represent the sum of squares of errors of GSPM, and it is also the minimum error of the three models, which demonstrate that the GSPM is suitable for the settlement prediction of an HTL.