# Floor Heave Mechanism and Anti-Slide Piles Control Technology in Deep and Large-Span Chamber
## 1 Introduction  
With shallow coal resources dried up and the demand for coal increasing in China, most of the coal mines in development are deep. Research has shown that maximum principal stress of some deep mining areas is vertical stress, which rises linearly with an increase in buried depth [1, 2]. Therefore, the deformation and failure of the surrounding rock in roadways and chambers are increasingly serious with the increase in mining depth [3, 4]. The problem of floor heave control in large-span chambers has especially become one of the main difficulties in deep mining. Many scholars have presented different opinions on the failure mechanisms and evolution laws of floor heave in recent years. [PERSON] et al. [5] obtained the plastic zone distribution, laws of deformation, and movement and stress distribution around the roadways without support by numerical modeling with Fast Lagrangian Analysis of Continua (FLAC) and in situ measuring. [PERSON] et al. [6] established a mechanical calculation model of the floor and deduced the expression of critical load of buckling floor heave according to the thin plate buckling theory of elasticity. By long-term site monitoring, [PERSON] et al. [7] indicated the main reason for floor heave in deep weak rock roadway is the open floor becoming the main place for deformation and stress release, and the weak broken floor rock is squeezed into the roadway under the action of in situ stress, under continuous plastic flow. [PERSON] et al. [8] studied the slip-line field of deep roadway floorby theoretical derivation, and deduced the expression of ultimate load and migration evolution characteristics of velocity field. [PERSON] et al. [9] studied the deformation mechanism of sliding floor heave through the theory of plastic mechanics, divided the floor rock mass into zones, and obtained the critical failure depth of sliding floor heave and the minimum support load required to maintain stability. [PERSON] et al. [10] considered the overall shear failure of floor rock mass under the action of the compression effects of two sides was the main cause of floor heave, which was similar to the overall shear failure in the foundation. [PERSON] et al. [11] agreed with the above point and found that the rock mass fragmentation of two sides caused natural unloading, and high stress transferred to the floor with the compaction of the sides' rock mass resulted in floor heave of roadways. [PERSON] et al. [12] found that under graded loading, the floor deformation belonged to extrusion uplift floor heave, the failure of two sides belonged to brittle fracture failure, and the surrounding rock at the floor corner was subject to biaxial stress dominated by horizontal stress, whose failure was shear compression failure by a similar simulation test. [PERSON] et al. [13] found that the main factors leading to floor heave included the low strength of the surrounding rock, high stress levels, and the obvious rheological effect of surrounding rock through the true triaxial test on site. [PERSON] et al. [14; 15] developed a large-scale geomechanical simulation test system suitable for simulating the whole process of excavation and support in deep roadways and studied the zonal fracture phenomenon of surrounding rock through the system. Some scholars have provided effective prevention methods for floor heave according to concrete engineering practices [16; 17], such as various types of contractible closed brackets [18], metal stents and inverted arches [19; 20], bottom grooving [21] and blasting pressure relief [22], and a combination of floor bolts [23] and grouting [24]. Considering the need to know the floor deformation and mechanical properties of floor rock, it is difficult to effectively control floor deformation with conventional reinforcement and support methods.