Research On The Key Technology Of Grouting Treatment In The Mined Out Area Under The High-rise Building

This paper takes the construction site of Evergrande health Valley Project in Yuntai Mountain as the research background,Through fully collecting mining data,field geological investigation,geotechnical engineering investigation and analysis calculation,the influence of the old goaf on the proposed building is systematically analyzed,Study on the key technologies and control measures in the construction stage of goaf treatment.To achieve the following research results:(1)Combined with the collected mining data,the technology of drilling,borehole imaging and field investigation are used to study the goaf site,It is found that there are still obvious cavities in the goaf of Two-1 coal seam,the fracture zone of Two-1 coal gob is developed,Under the current condition of the site,the goaf is not collapsed and dense,and there is a potential geological hazard,There are ground cracks,pebble layer and other hidden dangers affecting the construction in the site.(2)The factors such as the type of goaf,stoping time,coal seam mining method,roof management method and surface deformation characteristics are analyzed comprehensively,The mined out area of Two-1 coal seam with a buried depth of 50～150m is divided into unstable areas;According to the influencing factors of "activation" and the characteristics of goaf,the influence degree of goaf on the project is analyzed,There is a shallow gob of Two-1 coal seam with a buried depth of 50～150m in unstable area I1,which has a great impact on the proposed project The change of groundwater results in the "activation" of the old goaf,so that the shallow goaf has a medium to large impact on the proposed project,The additional stress analysis method shows that the number of building layers has a great influence on the stability of the underground goaf,The influence degree of buildings with different height on underground goaf is different;The area with 50～150m buried depth shallow goaf is evaluated as the area with poor suitability.(3)According to the characteristics of the goaf and buildings,the grouting area is divided into the goaf area with the buried depth less than 100 m and the multi～storey building area is constructed,The buried depth of the goaf is less than 100 m,and the buried depth of the goaf is less than 150 m in three areas of the high～rise building.Different design principles of grouting holes are adopted in each area;When the buried depth of the mined out area is less than 100 m,the slurry shall be stopped by the orifice;when the buried depth of the mined out area is less than 150 m,the slurry shall be stopped by the slurry stop plug;According to the characteristics of the site,the construction sequence of grouting holes and the characteristics of grouting materials are proposed,and the layout of grouting holes and grouting construction technology are defined.(4)Based on the field grouting test,the fluidity,injectability and water separation rate are comprehensively considered,The construction effect of cement slurry with water solid ratio of 1:1.2 is better;The initial setting time of accelerator with 2% specific gravity is about 25～30min,which is more convenient for construction;The gap connectivity of goaf is good,and the orifice pressure of grouting hole is controlled at 1～2mpa in principle,And adjust according to the principle of 0.15mpa/10 m,The grouting can be stopped when the ground deformation is serious or there is grout pouring on the ground;According to the characteristics of the pebble stratum,the following drilling measures are put forward to solve the problem of hole collapse.(5)The quality inspection method of grouting treatment is studied,The core drilling method,grouting stone strength test,in hole imaging,wave velocity test and grouting test,which are suitable for grouting detection of this project,are put forward;The test results show that the core is basically continuous and complete,and the representative value of natural uniaxial compression of core is 0.99～1.36mpa;The wall of the grouting section is relatively complete,and the filling rate is more than 95%.The wave velocity of the grouting section is 365～384m / s in the test of wave velocity in the hole.This thesis has 25 figures,28 tables and referred to76 articles.