## 5 Conclusions and Suggestions  
After carefully investigating the methods for stability assessment of cracked clay slopes and considering the drawbacks and deficiencies of currently available methods, an effective, practical, and relatively accurate stress mechanism of major crack initiation and development is proposed in this paper. A large-scale, arc-shaped slip surface clay slope model was constructed to verify the correctness of the proposed theory. Stress changes in the clay slope and the development of slope shoulder displacements under the set load sequence were monitored by EPCs and a displacement gauge. Based on the stress mechanism of major cracks, the locations and depths of the major cracks were determined. The relationships between the development of major cracks, stresses, and displacements during the progressive failure of a landslide were studied. The main conclusions and suggestions are as follows:  
1. The development process of major cracks is inherently consistent with the variation processes of horizontal stresses near the major cracks and slope shoulder displacements. In addition, the limit loads of horizontal stresses and displacements are consistent. When no cracks appear, the displacements increase slowly or uniformly, while the horizontal stresses increase uniformly. When a trailing edge crack occurs, the development of horizontal stresses and slope shoulder displacements begin to accelerate in general. The occurrence of the front edge crack causes the horizontal stresses of the nearby measuring points to appear as inflection points. At the same time, the slope shoulder displacements develop rapidly.
2. In the process of stress transfer and redistribution under loading, the horizontal stresses near the major cracks appear as inflection points and accelerated growth. The locations and depths of the major cracks could be determined by analyzing the horizontal stress differences between adjacent measuring points. It is recommended that horizontal stresses be used to reflect the development process of major cracks.
3. Due to the proximity to the slip surface, the appearance and development of the tension-shear vertical crack at the trailing edge have a more significant impact on the displacement of the slope shoulder and the horizontal stresses. Compared to the front edge shear diagonal crack, the trailing edge crack has a greater impact on the landslide.  
The perspective of major crack-stress-displacement extends the existing methods for assessing the stability of cracked clay slopes, which is helpful in grasping the relationship between the internal stress variation characteristics of clay soil mass and the macroscopic deformation characteristics of clay slope in the progressive failure process, and also provides a certain reference for landslide prediction. In the future, the authors will extend the theory discussed in this paper to relatively complex strata and working conditions (such as rainfall, earthquake, etc.) and apply it to actual engineering slope monitoring.  
Conceptualization and methodology, H.H. and Z.Z.; experiment, H.H., B.W. and W.Z.; data processing, B.W.; original draft, H.H.; writing and editing draft, H.H. and Z.Z. All authors have read and agreed to the published version of the manuscript.  
This work was funded by the National Natural Science Foundation of China, grant numbers 51478066 and 51178488.  
Not applicable.  
The data used to support the findings of this paper are available from the corresponding author upon request.  
The authors greatly thank [PERSON], [PERSON], and [PERSON] from the School of Civil Engineering and Architecture, Chongqing University of Science and Technology, and [PERSON], [PERSON], [PERSON], and [PERSON], from the School of Civil Engineering, Chongqing University, for their help during the experiment.