Experimental Study On The Characteristic And Technology Of Air-pressure Subsoiling

China is a country with a serious shortage of water resources.Researching the reasonable farmland cultivation technology,increasing the soil moisture storage capacity,reducing water and soil loss,avoiding the continued reduction of arable land are of great practical significance to realize the sustainable development of agriculture.In order to solve the soil and water loss caused by unreasonable tillage,our country has carried out the "conservation tillage" cultivation mode.Subsoiling is an important part of conservation tillage,by means of loosing soil,breaking the bottom of the plough and deepening the cultivation layercan,subsoiling could improve water permeability,breathability and aggregate structure of soil,making rain water penetrate into the soil more easily,thus contributing to crop root development,improving the water conservation capacity.However,the traditional subsoiling way of subsoiling shovel is to break the plow layer directly,and there are lots of problems such as small subsoiling influence area,shallow subsoiling depth,uneven subsoiling level.So researching and exploreing new ways is one of the important ways to overcome the weakness of the traditional way of subsoiling and to improve the effect of subsoiling.This paper presents a new method of subsoiling,air-pressure subsoiling,which injecting high pressure gas into the soil of the cultivated land to make the soil under the action of high pressure gas produce cracks,so that achieve the subsoiling of the cultivated land.In order to figure out the effect and the features of the air pressure subsoiling,and clarify the influence of subsoiling parameters on the evaluation index of subsoiling pressure,this paper studies from the following seven aspects:The main research content are as following:Analyzed the principle of crack formation and crack growth mechanism of the air-pressure subsoiling.Established the crack propagation model of air-pressure subsoiling.Analyzed the crack starting pressure condition by air-pressure subsoiling.Selected the evaluation index of the effect of air pressure subsoiling.Soil porosity and soil surface uplift were selected as the evaluation index of the effect.Given the test method for each evaluation index.And analyzed the test principle and described the test method.Designed the test device for air pressure subsoiling.Carried out the effect experiment of air-pressure subsoiling to verify the effect of the air pressure subsoiling.The results showed that:the high pressure gas mainly produces horizontal cracks in the soil,the porosity of the plough layer increases obviously with the development of the horizontal cracks,which can break the plough layer effectively,and increase the air content in the soil after subsoiling,make the soil volume expansion and uplift the soil surface,obtaine good subsoiling effect without disturbance or less disturbance of the tillage layer;air-pressure subsoiling for the bulk density of 1.6,1.8g/cm3 plough layer also has a good effect of subsoiling,the tillage layer and the bottom of the plow porosity are greatly improved after the subsoiling.It can overcome the problem that traditional subsoiling shovel is difficult to implement the subsoiling on the bottom of bulk density.The influence radius of air pressure subsoiling is 0.7m,which is 2 to 2.5 times of the influence radius of the traditional subsoiling shovel subsoiling,and the influence radius of subsoiling plough layer is at least 3 times more than traditional subsoiler.And the porosity increase rate is higher as the change range is smaller in the influence scope,which proved that the air-pressure subsoiling has lots of great characteristics,such as a wide range of subsoiling,subsoiling uniformity,high degree of subsoiling and so on.In order to get the significant influence of the air pressure subsoiling parameters on the evaluation index,analyzed the parameters of air pressure as subsoiling pressure,jet point depth,significant air jet hole angle and plow density rate and soil surface uplift on soil porositysubsoiling by orthogonal test.The results showed that subsoiling pressure,jet point depth,gas spraying hole of gun effect of increasing soil porosity and soil surface uplift rate significantly.In order to analyze the influence of air pressure on evaluation index.The effects of subsoiling pressure on soil porosity and soil surface uplift were analyzed by means of the whole factor experiment.The results show that the horizontal distance of soil porosity increase rate and soil surface uplift rate of porosity increased significantly;the maximum value appears in the same depth and jet hole of the plough layer,indicating the depth of gun jet holes of the same plow can get the best subsoiling quality,actual production should set a reasonable air jet holes depth according to different plough bottom depth;In lower bulk density,subsoiling pressure in the soil lateral diffusion and vertical diffusion coexist,porosity increased with pressure increasing rate had no significant change,with the horizontal distance increasing volatility and volatility;And in higher bulk density of the plow bottom,lateral diffusion tendency and pressure enhanced vertical diffusion is decreased,the porosity increased the rate increases as the pressure increases,with increasing distance from the level of volatility decreases and the amplitude is smaller;The increase of porosity and soil surface uplift rate caused by the increase of the pressure of the deep loosening soil is not obvious,but the increase rate of porosity and the uplift rate of soil surface caused by the lower bulk density are significant;For the plow bottom with bulk density of 1.4,1.6 and 1.8g/cm3,the porosity increases and soil air increase is maximum when the air pressure is1.4,1.8 and 2.2MPa respectively,illustrated that for the bulk density of 1.4,1.6 and 1.8g/cm3 of the plow bottom,useing the the subsoiling pressure of 1.4,1.8 and 2.2MPa respectively can get a better subsoiling effect.In order to explore the high pressure gas diffusion law through air pressure subsoiling,completed the simulation and analysis of the high pressure gas diffusion in the bottom of different bulk density by CFD software;The results showed that the high pressure gas was not easy to diffuse to the horizontal direction in the lower bulk density plow bottom,and the high pressure gas diffusion to the horizontal direction gradually increases with the increase of bulk density.Designed the general structure,key parts of the air-pressure subsoiling machine.This machine was towed by tractor,can realize the air-pressure subsoiling operation by continuous injection of high pressure gas inside the cultivated under the condition of no parking.The research results of this paper can provide reference for the research and development of air-pressure subsoiling technology and machine.