# Model Test of Micro-Pile Group Reinforcing High Steep Landslide
## 1 Introduction  
With the development of economic growth, much infrastructure is to be constructed in the mountainous areas of China. Hence, high and steep landslides are commonly encountered due to the construction in these areas. High and steep landslides often cause great economic losses and human casualties, which require effective reinforcement techniques to prevent landslides during construction. In general, the sites available for construction near high and steep landslides are small, and the common retaining structures, such as anti-slide piles, are not applicable. On the other hand, with the development of micro-pile technology, this technique has become an effective method to install steel pipe micro-piles at the top of high and steep landslides for reinforcement.  
Steel pipe micro-piles are a kind of micro-pile; their pile diameters are generally less than 30 cm. Steel pipe micro-piles are usually formed by a drilling rig, inserted into the steel pipe, and then filled with concrete, which has the advantage of fast construction speed,little disturbance to the landslide, and strong site adaptability. Micro-piles are increasingly used in landslide prevention projects [1; 2; 3; 4; 5; 6; 7; 8; 9; 10] and have been studied by many scholars. For example, through field tests, [PERSON] [11] preliminarily studied the relationship between the lateral load acting on a single micro-pile and the required pile length. [PERSON] et al. [12] investigated the lateral load-bearing performance of micro-piles. [PERSON] et al. [13] carried out a detailed analysis on the performance of micro-pile groups with rigid caps under lateral loading through model tests. Several model tests to illustrate anti-sliding performance of steel pile groups were also proposed by many researchers [14; 15; 16; 17]. Hence, the micro-pile-slog movement reaction was well understood throughout the test results as relating to the stress distribution and failure mechanisms of micro-pile groups [18; 19; 20]. Based on recent field test results, the use of micro-piles in landslide prevention has been proven to be an acceptable method, and some real projects have also been conducted in China [21; 22]. However, these previous studies mainly focused on the micro-piles placed on the front edge of the landslide, because the front edges of most landslides are relative gentle. Meanwhile, in Western China, many high and steep landslides existed where micro-piles may not be constructed on the front edge of these slopes due the limited space. Hence, the new technique of implementing steel pipe micro-pile groups on the tops of landslides is of great importance for high steep landslide prevention, and is not yet fully understood. Meanwhile, steel pipe micro-pile use steel pipes as reinforcement, which has some differences from reinforcement forms such as steel reinforcement cages and steel tendons in terms of mechanical properties. For engineering construction needs, it is necessary to study the force-deformation characteristics of steel pipe micro-pile groups in high and steep landslide reinforcement.  
In this study, in order to further our understanding of the performance of the micro steel pipe group on the prevention of high steep landslides, a large-scale physical model test was conducted to test the interaction between steel pipe micro-pile groups and high steep landslides. The landslide model is made of compressed loess, with an artificial sliding surface. The landslides were triggered by step-loading at the top of the landslide. The force, deformation law, and damage mode of steel pipe micro-pile groups in high steep landslides are investigated in detail. The test results may provide a scientific basis for a design method for slope disaster prevention.