| With the development of economy,more and more cavern projects are carried out accordingly.The underground working conditions are complex and changeable,and its stability is related to the safety of personnel and property.The weak interlayer is a geological feature that is often encountered in the design and construction of cavern and is also a key variable that affects the stability of cavern.Aiming at the surrounding rock stability problem of caverns containing weak interlayers,this paper prepared ultra-low strength self-compacting similar materials under the guidance of similarity theory,designed by orthogonal test,and adopted indoor model test as the means to explore a new method of model test molding.On this basis,a cavity model containing weak interlayers was made.The influence of cavern section shape,sandwich dip Angle and position on the stability of surrounding rock of cavern is studied.Finally,numerical simulation is carried out with ANSYS software to verify and extend the indoor model test and conclusion,so as to provide more reliable guidance and suggestions for practical engineering construction.The main research contents and conclusions are as follows:(1)The molding process of the indoor model was improved,and five factors including the ratio of cement to sand,the ratio of water to binder,the content of thickening agent,the content of fly ash and the content of water reducing agent were adjusted.The influence rule of each factor change on the self-compacting performance of similar materials was explored,and the similar materials with excellent selfcompacting performance were prepared,which was more in line with the theoretical assumptions of the similar model.The results show that thickening agent has the most significant influence among the admixtures,and the optimal proportion is 3%.When the cement-sand ratio increases from 1/7 to 1/4,the water-binder ratio decreases from 1.55 to 1.4.In the final root test,the dosage of water reducing agent should be adjusted appropriately by 1%-3%.(2)On the basis of ensuring good self-compacting performance of similar materials,the bone glue ratio,cement content and expansion agent content were adjusted to explore the evolution law of physical and hydraulic property parameters of similar materials with the ratio.The bone glue ratio of the main rock mass material of the model was determined to be 3,60% cement content and 0% expansion agent content,and the bone glue ratio of sandwich material was determined to be 6,60% cement content and 15%expansion agent content,providing ultra-low strength self-compacting similar materials for subsequent tests.(3)The influence law of cavern section shape,dip Angle and position of weak interlayer on the stability of surrounding rock is studied.The vertical and horizontal deformation of the surrounding rock and the time to enter the stable deformation stage were taken as the results of orthogonal analysis,and the above three analysis results were taken into consideration.The position of interlayers should be given priority,and the position of interlayers less than 1.5 times the hole diameter should be avoided as far as possible.At the same time,interlayers with large dip Angle of 30° to 60° should be selected,and those with small dip Angle within 30° should be avoided.Finally,the section shape of straight wall semicircular arch should be the first choice,followed by circle.(4)The ANSYS numerical simulation software was used to extend the laboratory test,and each factor was increased by one level.The conclusion was similar to the model test,that is,the feature factors of interlayer were given priority,and the position of interlayer was as far as possible to avoid being less than 1.6 times the diameter of the hole,and the interlayer with a small dip Angle within 30°.The second section shape was straight wall semicircular arch and circle.The results of laboratory model test and numerical simulation test are mutually verified and extended. |
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