**3. Integrated analysis methods of slope stability analysis and maintenance**

#### **3.1 Introduction**

**Figure 1** is an integrated analysis method for stability analysis and maintenance of cut-slopes.

The integrated analysis method presented in this study is divided into 14 steps. It is divided into three sections. In the first section, the geometric of the slope and the finite element model of FEM are generated. And, to consider the time-dependent deterioration, the SRF is applied to the strength parameter of the soil (step 1 � 3). The integrated analysis method proposed in this study is based on the cut-slope and only the strength degradation caused by the time-dependent deterioration is taken into consideration. The proposed method can be used both as soil and rock as a material of cut slope, but the only soil is considered in this study.

In the second section, slope stability analysis is performed using FEM. The FOS is calculated by the SAM and the behavior up to the slope failure is analyzed by the nonlinear static analysis with*k*<sup>0</sup> condition. The displacements until the slope failure analyzed using the slope stability analysis plot the cumulative displacement curve,

**Figure 1.** *Mesh and boundary conditions of slope stability analysis.*

velocity curve, and inverse-velocity curve and, applied to the maintenance methods of the slope. The strength degradation of the soil due to the time-dependent deterioration phenomenon was quantified by SRF. However, geological factors and strength degradation due to groundwater cannot be considered. Therefore, the proposed method in this study cannot be applied when the groundwater level is located on the predicted failure surface of the slope.

In the last section, the results of the slope stability analysis are applied to the maintenance method. A typical sensor used for slope maintenance is an in-site inclinometer, which is applied to SPC using slope stability analysis results at the same point. Next, a mathematical failure model of the slope was predicted using a cumulative displacement curve. And the time of the slope failure was predicted using an inverse-velocity curve and, compared the formulation of Fukuzono [1]. Finally, the collapse behavior of Selborne in the United Kingdom and Kunini Slope in Japan, as reported by Petley [34], was compared.

**3.2 Analysis procedure**

**Figure 2.**

**163**

In this section, detailed description is given for each step according to the

*A flowchart on integrated analysis methods of slope stability analysis and maintenance of the slope.*

*Integrated Analysis Method for Stability Analysis and Maintenance of Cut-Slope in Urban*

*DOI: http://dx.doi.org/10.5772/intechopen.94252*

2. Step 2: In the FEM, the soil uses the Mohr-coulomb model. The soil

*c* 0 *<sup>f</sup>* <sup>¼</sup> *<sup>c</sup>*<sup>0</sup>

*SRF* (5)

1. Step 1: This is the step of generating the geometry and mesh of the slope. And the load and boundary conditions acting on the slope. In general, only selfweight is considered. Please refer to the literature on FEM [10, 11, 29].

investigation is performed to calculate the cohesive and internal friction angle,

3. Step 3: The strength parameters of soil are to be decreased according to the SRF, and the cohesion of soil at the point of failure and the internal friction angle are as expressed in Eqs. (5) and (6), respectively. In the case where the SRF is used, the value of initial strength reduction factor (SRF) and the value of increment should be determined. The values of 1.0 and 0.05 of the strength factor and increment are frequently applied to the method of general strength reduction. The final strength reduction coefficient will be a value at the stage

flowchart shown in **Figure 2**. The details are as follows:

which are the strength parameters of the soil.

failed to converge in the nonlinear static analysis.

**Figure 2** in this study improves the problem of the slope stability analysis method that only estimates the FOS and, the problem of maintenance method that fails to evaluate clear management criteria and failure behavior of slope. It also combines the advantages of slope stability analysis and maintenance method based on measured data [35, 36]. Slope stability analysis is used to determine the failure behavior and FOS of the slope. And, it can be applied to the maintenance method to predict the management criteria of statistical process control method, a mathematical failure model of slope, and the time of slope failure.

In the maintenance of the slope, the surface displacement is usually tension wire, and the ground displacement is the inclinometer. Because the displacement of the entire slope is analyzed using the FEM, that can be applied to the management criteria of the displacement measuring instrument installed on the slope. In particular, the displacement at the crown of the slope is very important, which can be measured both by tension wire and inclinometer. There are two maintenance methods presented in this study. First, the failure model is calculated by the cumulative displacement curve of the slope. And the displacement according to the depth is applied to the SPC method to judge the occurrence of abnormal behavior of the slope. If only tension wire is applied to the maintenance of the slope, the formation of the failure surface cannot be confirmed because only the surface displacement of the slope can be measured. Because the inclinometer measures the displacement of the whole underground, it has an advantage that it can easily judge the failure surface. Therefore, the inclinometer was applied to the slope instrument in this study. Please refer to KICT [20] for the advantages and disadvantages of both measurement devices.

*Integrated Analysis Method for Stability Analysis and Maintenance of Cut-Slope in Urban DOI: http://dx.doi.org/10.5772/intechopen.94252*

**Figure 2.** *A flowchart on integrated analysis methods of slope stability analysis and maintenance of the slope.*
