Study On Fine Content Characteristics Of Stone Under Shear-Compression Load

The particle size of manufactured sand is between 0 mm and 4.75 mm,and the stone powder content is the particle content with a particle size less than 75 μm in manufactured sand.Stone powder is an inevitable product of manufactured sand.Studies have shown that manufactured sand containing a certain proportion of stone powder can help improve the strength of concrete,while excessive stone powder content is not conducive to the improvement of concrete strength,so the control of stone powder content is very necessary and urgent.At present,the stone powder content is mainly controlled by detection,cleaning and other links,which have high control costs and low efficiency.This paper studies the characteristics of stone powder production in the process of load loading,and provides data basis and theoretical reference for the process control of stone powder content in the production process.This paper takes sand making and powder production as the main evaluation indicators,and uses Tavares Breakage Model different from traditional Bonded particle model(BPM)to simulate and analyze the powder production characteristics of limestone particles,and discusses the influence of shear extrusion load on the powder production characteristics of sandstone particles.The paper takes the jaw crusher with shear extrusion load as a common loading mode,uses response surface method to construct the mathematical model of powder production and sand making characteristics,and verifies it by experiment,and obtains the following main conclusions:(1)To improve the accuracy of computer simulation,calibration experiments were conducted.An electronic universal testing machine was used to perform limestone compression tests,and the relationship between different particle crushing modes and powdering characteristics was analyzed.The crushing strength and ultimate strength of limestone particles with different sizes were statistically evaluated,and the Weibull distribution function was applied to describe their distribution patterns.The calibration experiment of particle crushing and powdering was completed,which provided experimental reference for calibrating the parameters of the Tavares Breakage Model for limestone particles.(2)The Tavares breakage model was used to build and validate a simulation model of particle breakage and powdering,as the conventional models could not effectively simulate this process.Based on the discrete element method,the selection of limestone particle crushing model was discussed,and the data fitting of simulation parameters for limestone single particle crushing was completed.With the goal of force displacement curve and particle size distribution curve after crushing,the simulation and experimental results were compared,verifying the correctness of the parameters.(3)A mathematical model of particle shear extrusion load and crushing sand powdering was established and tested with a jaw crusher.Using Box-Behnken experimental design method and the calibrated Tavares Breakage Model parameters,a jaw crusher simulation model with different feed size,loading frequency,discharge port and feed port was built and validated by regression analysis.The response surface of limestone particle crushing sand powdering parameters in discrete element method was obtained.The parameters were optimized based on powder output and sand production as objectives,and the effects of various factors on these outputs were studied.This provided scientific guidance for future particle group simulation and equipment powder control for related crushers.