Research And Application Of Single-liquid Flexible Mold Pumping Prop Material Through Goaf

There are often some special-purpose roadways in the coal seam of the coal mine working face,among which there are some irregular mining roadways,commonly known as empty roadways.When the working face is passing through the empty road,accidents such as roof fall and frame pressing are very likely to occur,which seriously affects the production safety.Therefore,reasonable support for the empty road is a necessary means to ensure production safety.It is of great significance to study a new type of pumping material,which can be applied to the flexible mould pumping prop to support the empty roadway.Sulfoaluminate cement clinker is matched with gypsum lime,and can prepare slurry material for pumping props.The construction process of this material is simple and fast,and the hardening strength meets the requirements,and it has the prospect of wide application.In order to control the reaction time of the material,optimize the reaction process of the material and grasp the reaction mechanism,a series of experimental studies on the material need to be carried out.In view of the above problems that need to be studied,this paper firstly studies the mixing ratio of the three raw materials of sulfoaluminate cement clinker,gypsum and lime,and explains the reaction process from the product point of view;secondly,studies the effect of different kinds of admixtures Then,the influence law under the combined action of admixtures was analyzed by orthogonal test,and the optimal mixing ratio was screened out.Finally,the industrial test was carried out and good results were obtained.The main research content of the paper is divided into the following four aspects:(1)The ratio and reaction characteristics of raw materials were explored.The addition of gypsum to sulfoaluminate clinker has the effect of retarding setting.The rate will also continue to increase with the increase of gypsum content.However,the addition of gypsum did not significantly change the p H of the slurry.Gypsum can effectively increase the compressive strength of materials.The addition of lime will increase the p H value of the material slurry,shorten the setting time of the material,and the appropriate dosage can improve the material.In addition,it was also found that lime has a great influence on the expansion of the material.When the amount of lime is large,the phenomenon of expansion cracking will occur after the material is hardened.The analysis of hydration products by XRD shows that there is surplus after the gypsum content exceeds 30%,and the main product is ettringite.The addition of lime will promote the amount of gypsum participating in the reaction,and will not change the type of product.(2)The main effects of 4 retarders,3 water reducers,2 lithium salts and ZQ1 enhancer were experimentally studied.The research results found that sodium gluconate has a good retarding effect and meets the requirements of the material;polycarboxylate superplasticizer has the most obvious effect on the initial fluidity;lithium carbonate and lithium hydroxide have obvious effects on the early strength of the material,considering the economic benefits,lithium carbonate was finally selected as the coagulant;the self-developed ZQ1 early strength agent has a significant effect on the 14-day compressive strength of the material.(3)Through the orthogonal test,the change rule of each index under the combined action of admixtures was analyzed.Finally,the optimal admixture dosages are 0.2% retarder,0.3%water reducing agent,0.15% lithium carbonate,and 2% ZQ1.It takes 20 minutes to reach a fluidity of 300 mm,which fully meets the construction requirements and can withstand compression within 2 hours.The strength can reach 4.68 MPa,and the 28-day strength can reach 19.12 MPa,which meets the general engineering strength design requirements.(4)On-site support test was carried out on a certain working face of a mine passing through a parallel empty roadway,the number of pillar arrangements was determined by calculating the bearing capacity of the pillars,and the construction process was studied in detail.The roof and floor heights and the pressure on the struts were monitored.Finally,the working face passes through the empty road quickly and safely,and the pillar achieves a good supporting effect and saves the cost.