Effects Of Fracture On Hydraulic Properties Of Stalk Composite Pipe

As a new type of subsurface irrigation method,Stalk Composite Pipe(SCP)irrigation is different from subsurface irrigation in the traditional sense,which has the conditions of subsurface irrigation and the function of straw returning to the field,and has the advantages of green environmental protection and easy recycling,which is of great significance for the recycling and utilization of agricultural resources and the development of green irrigation agriculture.In this paper,the effects of fracture mode and fracture spacing on the hydraulic performance of SCP were experimentally studied with the fracture method and fracture spacing as the entry point.The test is divided into free outflow test and buried test,through the free flow test,preliminary analysis of SCP in different fracture methods and fracture spacing under the water flow can pass through the fracture;on the basis of this test,buried test,buried test is divided into different fracture methods and different size of the fracture spacing two groups of tests,both selected orthogonal test,analysis of different fracture conditions on the SCP pressure head,water seepage rate,irrigation uniformity and soil moisture content.Understanding the hydraulic performance of SCP in the fracture state is of great significance for promoting the mechanized application of SCP irrigation.The main conclusions are as follows:(1)Under the condition of free outflow,the pressure in the broken SCP is continuous,and the water flow can pass through the fracture.At the working pressure,with the increase of irrigation time,the pressure of each measurement point and before and after the fracture is continuously increasing and then tending to be stable,reaching a stable time of 30 minutes after the start of the test.The spacing of the fracture has the greatest impact on the pressure distribution and water infiltration rate of the SCP,the larger the spacing between the fractures,the more unfavorable it is to the water flow through the fracture;the fracture mode has the second impact on the pressure distribution and water infiltration rate in the pipe,and the straight cut is more oblique,which is more unfavorable to the water flow through the fracture,and the straight cut of 6 cm in this study is most unfavorable to the water flow through the fracture.Under the same fracture spacing,the water leakage rate of straw composite pipe treated by D1 is greater than that of D3 treatment,and under the same fracture method,the water leakage rate of straw composite pipe increases with the increase of fracture spacing.(2)Under buried conditions,the fracture mode is different,the stable pressure head in the complete SCP tube is higher than that of the broken SCP;the relationship between the pressure distribution in the SCP under different fracture methods is: straight cutting < oblique cutting(45°)< free(broken);under different fracture modes,the relationship between the water leakage rate of the SCP is: oblique cutting(45°)> straight cutting > free(broken);straight cutting and miter cut are not conducive to water flow through the fracture,and free fracture has less impact when the water flow passes through the fracture.In this study,the maximum working pressure of fractured SCP was recommended to be 50 cm.In the application process of SCP,there may be a variety of fracture methods,as long as the spacing does not exceed the 1 cm range in the test,it will not have much impact on its irrigation effect.(3)Under the conditions of burial,the spacing is different,and the stable pressure head in the SCP in the complete state is greater than that of the SCP in the fractured state,and the working pressure is the same as the water head,and the stable water head of the SCP under the spacing of the three fractures is not much different.When the working pressure exceeds50 cm in the test,the pressure head in the tube in the stable state of infiltration does not rise much,therefore,it is recommended that the working pressure of the SCP should not exceed50 cm during the application process,and the gap between the breaks can be controlled within the range of 6 cm,and the impact on it is not too big.The preliminary exploration of the hydraulic performance of SCP under fracture conditions shows that SCP can still meet the requirements of underground irrigation under fracture conditions.Comprehensive analysis,in the actual production application process,attention should be paid to the spacing of the fracture is controlled within 6 cm,and the working pressure is not more than 50 cm,so that the irrigation effect of the SCP has less impact and its irrigation performance can be realized.