Experimental Study On Roughing Resistance Of Crushed Stones In River Model

The river model is an important means to study hydraulic engineering and solve practical engineering problems,and the roughening of the model is the main method to satisfy the similar resistance of the model.At present,the river model is close-packed and most use pebble particles.Now it is found that there are various sizes of crushed stone on the market,which is more convenient to obtain.At the same time,the crushed stone’s edges and corners are distinct,which is more conducive to the roughening of the distorted model requiring greater resistance.The river model can be widely applied.Crushed stone’s roughness and its roughening method have not been studied in detail yet.In this paper,the combination of theoretical analysis,numerical calculation and flume experiment is used to study the uniform-like close-packed crushed stone,the roughness of the slurry and gravel mixture and its resistance coefficient,which can provide reference for the river model experiment.The main contents and research results of the thesis are as follows:(1)It is pointed out that the statistical sample weight of the average nominal diameter of common gravel in the market is 1~10kg.Collecting four kinds of crushed stones,such as“stone powder”,“01”,“12”and“13”,which are commonly found in the market.According to the statistical analysis of the variation of average nominal diameter with sample weight,indicating that the sample weight is 1~10kg.(2)Through the two-dimensional flow numerical simulation,the flume experiment design is guided according to the uniform flow range of the flume.Based on the roughness of the pure slurry known by the specification,the two-dimensional flow mathematical model was verified and the basic parameters suitable for studying the roughness of the flume were given.Through the numerical simulation,the uniform flow range of the flume is obtained,so as to guide the flume experiment.The experiment range is 3m~13m from the inlet of the flume,and the total length of the flume is 20m,which satisfies the requirement of uniform flow.(3)It is pointed out that the section comprehensive resistance hydraulic radius division method is more suitable for estimating bed roughness.According to the four resistance division formulas,the roughness coefficient of the uniform-like close-packed crushed stone are calculated,and the calculation accuracy and applicability of each division formula are compared.It is considered that the section comprehensive resistance hydraulic radius division method is more suitable for estimating bed roughness.(4)A formula for calculating the roughness of the uniform-like close-packed gravel is established.Through the close-packing roughening experiment of uniform-like close-packed crushed stone on the bed roughness,the bed roughness was calculated by four resistance division formulas,and the experimental data were fitted by numerical fitting method to establish a formula for calculating the roughness of the uniform-like close-packed gravel.(5)The effect of slurry ratio on the roughness of the slurry and gravel mixture was studied.Through the roughness experiment of the slurry and gravel mixture on the bottom of the flume,the roughness coefficient of the slurry and gravel mixture was calculated by the hydraulic radius division formula.The relationship between the roughness coefficient of the mixture and the ratio of the slurry,the particle size of crushed stone was analyzed.(6)The variation characteristics of resistance parameters such as crushed stone resistance coefficient f and roughness Ks are explored.In this paper,the Darcy resistance coefficient f and roughness Ks of uniform-like close-packed crushed stone are calculated,and the relationship between Darcy resistance coefficient f and roughness Ks with flow rate Q,gravel particle size d,and bed roughness n_b is investigated.And the corresponding law is drawn.