Study On The Propagation Characteristics Of Ultrasonic Wave In Farmland Soil

With the increase of population in China,the loss of cultivated land is serious.To ensuring the bottom line of not less than 1 billion 800 million mu of cultivated land,it is an important to China’s grain security.In order to ensure the cultivated land area,we need to develop new cultivated land or waste land in time.Undeveloped and abandoned farmland would have hard foreign bodies such as stone,metal,glass slag and wood piles.This hard foreign matter will damage the agricultural machinery not only in the course of operation,but also endanger the safety of human and animal.The study of hard foreign object detection technology in farmland to realize active detection and collection of hard foreign objects can avoid hard foreign objects to damage agricultural operation machinery and prolong the service life of agricultural machinery.Although there are many studies on the propagation of ultrasound in soil media,but there are few studies on the application of ultrasound to the detection of hard foreign bodies in farmland soil.We are not sure how hard foreign bodies in agricultural soil affect ultrasonic transmission and how to detect hard foreign bodies in soil by ultrasonic waves.In order to apply ultrasonic wave to the detection of hard foreign bodies in farmland,the propagation characteristic of ultrasonic wave in soil rock mixture will be explored in this paper.The ultrasonic speed,attenuation coefficient and accuracy of ultrasonic echo in detecting hard foreign matter are summarized.In order to sum up the propagation rule of ultrasound in soil and the influence of block stone on ultrasonic propagation in soil.The main innovations of this paper lie in the following two points: first,the application of ultrasound in farmland soil.This is mainly about the influence of the stone in the soil on ultrasonic propagation when the ultrasonic wave propagates in the soil.The influence of the ratio of earth rock on ultrasonic propagation is quantitatively analyzed by comparing the soil and rock mixtures with different soil and rock ratios.Two.The purpose of this study is to detect hard foreign bodies in farmland soil.Although the hard foreignobjects in farmland soil will have a certain impact on agricultural machinery operation,but because of the low degree of Agricultural Mechanization in our country,the hard foreign body of farmland has not caused serious harm to agricultural machinery,so there is no study on the detection of hard foreign body in soil before.With the gradual upgrading of human cost and the gradual promotion of agricultural machinery,the impact of hard foreign soil on agricultural machinery will gradually become more prominent.This paper is the first to systematically explore this issue.This study is prospective.First of all,this paper introduces the research progress of ultrasonic in geotechnical media,and summarizes its existing problems.In order to detect damaging foreign bodies in farmland environment,ultrasonic nondestructive testing technology will be applied to soil environment.And the ultrasonic testing of the damaged foreign bodies in the farmland environment is carried out.Two ultrasonic tests were designed to meet the needs of this study.In the first experiment,the soil was divided into sand,loam and clay according to particle size,and sand and loam were taken as test soil.The damaged foreign objects in the actual farmland include hard and sharp objects such as block stone,metal,glass,tree pile and so on.These objects are the most common block stone,so the block stone is also the main object of this article.The influence of the content of soil in the soil on ultrasonic velocity and attenuation coefficient is obtained through experimental analysis.Different soil and rock composition and earth rock ratio are used as variables to explore the ultrasonic speed and attenuation coefficient of ultrasonic wave in rock and soil mixture.In the experiment,sand and loam were used as test soil,and white jade and corundum spheres were used as test blocks.The experimental results show that the ultrasonic velocity and attenuation coefficient have a good correlation with the ratio of rock to soil.With the increase of the proportion of rock and soil mixture,the amplitude of acoustic wave decreases and the sound velocity decreases.In order to achieve fast nondestructive testing,a nondestructive testing experiment based on reflected wave is also carried out.In order to avoid the attenuation of ultrasonic wave in soil transmission,the reflection wave test uses water as the medium of propagation.The following three factors are taken: the velocity of the wave source,the depth of the hardforeign body in the water,and the volume of the hard foreign body.Among them,the moving velocity of ultrasonic wave source is four levels of 1cm/s,3cm/s,5cm/s and 7cm/s;the hard foreign body is assumed to be a sphere,and the radius of the sphere is taken at the three levels of 1cm,3cm,and 5cm to carry out all factor experiments.This paper summarizes the propagation law of transmitted wave in soil environment and verifies the detection scheme of reflected waves in liquid media.The ultrasonic speed and attenuation coefficient of ultrasonic wave in soil environment were mainly tested.The test results show that ultrasonic testing is a reliable nondestructive testing method,and it can be used to detect the density of rock in rock and soil.When the density of block stone is higher(0.63),the sound speed and attenuation coefficient of different soil and block type samples will also be different.The relationship between the density of block stone and the sound speed and attenuation coefficient is also verified by experiments.Finally,the experimental results are analyzed theoretically.According to the test data,the mass ratio of rock mass in rock samples is negatively correlated with the sound speed,and the attenuation coefficient is positively correlated.According to the test results,the relevant acoustic and electrical parameters of ultrasonic soil hard foreign body detector were determined.The reflection test of water body verified the interaction between hard foreign matter and ultrasonic echo signal.