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Journal of Drainage and Irrigation Machinery Engin
 
2021 Vol.39 Issue.6
Published 2021-06-25
1
2021 Vol. 39 (6): 1- [Abstract] ( 11 ) [HTML 1KB] [ PDF 11058KB] ( 227 )
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2021 Vol. 39 (6): 2- [Abstract] ( 14 ) [HTML 1KB] [ PDF 1107KB] ( 283 )
541 Static analysis on rotor of the vertical turbine used for offshore platforms
ZHANG Jinfeng*,SONG Haiqin,ZHANG Fan,YANG Zhijun,LAI Liangqing
In order to investigate the static characteristics of the vertical turbine rotor, the type XBC18-178-240LC3 vertical turbine was chosen as the study object. First of all, a three-dimensional mathematical model of fluid flow in the vertical turbine and a physical model for the rotor system of the vertical turbine were generated by Creo according to design parameters and the flows of the vertical turbine with three-stages were simulated numerically by CFX under six conditions of 0.20Qd, 0.65Qd, 1.00Qd, 1.20Qd, 1.40Qd and 1.50Qd. Then, the physical model was imported into ANSYS Workbench and constraints were ad-ded to it according to the actual running environment. Finally, the numerical simulation results of flow field were imported into the physical model of the structure to realize the unidirectional fluid-structure interaction and then the static characteristics on the rotor system of the vertical turbine with the prestress were analyzed. It is demonstrated that the fluid pressure inside the impeller increases as the stage of the impeller increases and decreases as the flow increases; the maximum of the total deformation is located at the edge of the rear cover of the third-stage impeller and the maximums of the equivalent stress and equivalent strain are located at the intersection of the edge of the rear cover and the blade outlet in the third-stage impeller, which decrease with the increase of the flow; the maximum of equi-valent stress of the rotor is 118.23 MPa under four conditions of 0.20Qd, 0.65Qd, 1.00Qd and 1.50Qd, which is smaller than its allowable stress(250 MPa)and meets strength requirement;the pump′s working speed of 1 485 r/min is less than its first-order critical speed of 0.85 times, which meets the dynamic design requirement. Therefore, the vertical turbine of XBC18-178-240LC3 model meets the design and use requirements under safe operating conditions.
2021 Vol. 39 (6): 541-547 [Abstract] ( 37 ) [HTML 1KB] [ PDF 3299KB] ( 388 )
548 Influence of annular groove position on cavitation performance of high-speed inducer
CHENG Xiaorui*,YANG Dengfeng,LIU Mingjian
In order to suppress the cavitation instability caused by tip clearance leakage vortex of the high-speed inducer, a structure(that is, an annular groove)that can absorb the leakage vortex on the upstream and downstream of the high-speed inducer was set up, and 5 kinds of annular groove schemes were designed, the inhibition mechanism of cavitation by different annular groove schemes was studied by means of experiment and numerical calculation. The study finds that the cavitation first appears at the position where the leading edge of the suction surface of the inducer intersects the shroud, as the pressure at the inlet of the pipeline continues to decrease, the cavitation will continue to develop into the inducer passage and then spreads to the back of the centrifugal impeller blade, the annular groove can effectively inhibit the occurrence of clearance leakage vortex cavitation, asymmetric vortex cavita-tion and rotating vortex cavitation. The inlet pressure and the head of the centrifugal impeller are improved almost without affecting the efficiency and the head, the cavitation performance of the centrifu-gal pump is improved effectively. But at the same time, it is found that when the axial distance between the annular groove and the inducer is L3=-10.0 mm and L4=-12.5 mm, it will interfere with the flow state of the fluid in the inducer, affecting the work and energy exchange of the inducer, that is, when the annular groove is matched with the inducer, there is the best axial position between the two. At this time, the axial distance between the annular groove and the inducer is L1=2.5 mm.

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2021 Vol. 39 (6): 548-554 [Abstract] ( 27 ) [HTML 1KB] [ PDF 15845KB] ( 265 )
555 Effect of solid concentration on circulation flow and hydralic characteristics in vortex pump
QUAN Hui*,KANG Lei,GUO Ying,CHENG Jing,YU Xinyang,QUAN Sizhe
In order to study the effect of solid concentration on the structure of the circulation flow in the vortex pump, the 150WX-200-20 vortex pump was taken as the research object. The theory of fluid dynamics and the Eulerian two-fluid model was used. Six mixed fluid of solid and water were used as the flowing medium. The solid concentration was changed from 10% to 35%. Numerical simulation analysis was performed on the vortex pump. The variation rules of the streamline of the flow field in the vortex pump were compared and analyzed. The vortex core positions and shapes of the vortex structure on four 1/4 cross-section arrays with the axis as the center in the pump were studied at different concentrations. The results show that in solid-liquid two-phase flow, a set of main circulation flow I and a set of secondary circulation flow Ⅱ are formed in the vortex pump under the action of the impeller. The main circulation flow transfers the fluid acting at the inlet to form another set of secondary circulation flow Ⅲ. The intervention of solids will weaken the strength of the vortex and inhibit the expansion of the vortex structure area of the cross-section Ⅱ. A flow model of the vortex pump is proposed. With the increase of solid concentration, the variation range of the main circulation flow with the increase of flow in the non-leaf cavity is reduced. Under the operating conditions of the vortex core in the non-leaf cavity, the efficiency increases with the increase of the flow. After the flow increases into the impeller domain, the pump efficiency decreases. At the high efficiency point 1.2Qd, the larger the solid concentration, the smaller the distance between the vortex core and the axis. Under the operating conditions of the vortex core in the non-leaf cavity, the value of the shape coefficient of the vortex structure on the cross section is larger at the high-efficiency point 1.2Qd, and the shape of the vortex structure is relatively flat.
2021 Vol. 39 (6): 555-561 [Abstract] ( 25 ) [HTML 1KB] [ PDF 12690KB] ( 269 )
562 Performance prediction of centrifugal pump as turbines—a review and prospect
LIN Tong,*,ZHU Zuchao,LI Xiaojun,XIE Jing
In high energy-consuming industries such as chemical, petroleum and mining, there is a large amount of high-pressure fluid discharged directly through pressure reducing valves, resulting in a large amount of energy waste. The use of centrifugal pumps as turbine(PAT)to recycle this energy is an economic and practical method, but the performance prediction of centrifugal PAT is one of the key technologies and difficulties in its application. So the research progress of centrifugal PAT in perfor-mance prediction at home and abroad in recent years are systematically summarized, and an outlook on the future research is provided. Firstly, the research and progress of centrifugal pumps for the prediction of high efficiency point and full working condition characteristics of PAT are summarized and reviewed: In the prediction of high efficiency point of PAT, the flow and head conversion factors of pump and turbine operating conditions are calculated by empirical prediction, theoretical analysis and intelligent algorithm prediction. In the prediction of the full working conditions of the PAT, experimental fitting, theoretical analysis, numerical calculation and other methods are used to reveal the conversion relationship between the turbine under the partial working conditions and the optimal working conditions. Finally, some problems in the current research are discussed and the future research directions are prospected.
2021 Vol. 39 (6): 562-568 [Abstract] ( 35 ) [HTML 1KB] [ PDF 1376KB] ( 474 )
569 Effect of differential rotating shell on roto-jet pump performance
HUANG Qi*,LIU Zailun,WANG Xiaobing,LI Qifei,QUAN Hui,WANG Dongwei
Taking the roto-jet pump as test object, the performance test of rotating shell and impeller with synchronous variable speed and numerical study of non-synchronous differential speed between rotating shell and impeller were completed. To avoid the assumption of isotropic eddy viscosity,RSM linear pressure-strain model of Reynolds gravity was selected for numerical calculation and the numerical results were compared with the experimental results to verify its reliability.The results show that in the variable speed experiment, the flow rate and head of the test pump conform to the similar law, and the optimal efficiency remains basically unchanged. The maximum deviation of the optimal efficiency at each speed is 3.1% and tends to be constant.In the differential speed experiment, the rotating shell speed increased causes the radial liquid pressure gradient to increase, resulting in the increase of the liquid pressure in the area of r>r2 and the decrease of the liquid pressure in the area of r<r2. Affected by the differential disturbance between impeller and rotating shell,the turbulent kinetic energy values in the inlet and wake region of the collecting pipe are generally high and the energy loss is large. The size, shape and position of vortex center change with the rotating speed of rotating shell and are mainly distributed in the impeller outlet and flow center area. Compared with rated working condition, increa-sing the rotating speed of shell will improve roto-jet pump head, but increasing liquid energy depends on rotating shell wall friction and reduces the efficiency of the pump. The lower rotating speed of the rotating shell within a certain range is beneficial to improve the pump efficiency. Optimal rotating speed ratio between rotating shell and impeller is 0.75.The results are helpful for differential operation of roto-jet pump in the future.
2021 Vol. 39 (6): 569-575 [Abstract] ( 32 ) [HTML 1KB] [ PDF 14861KB] ( 276 )
576 Review of wave compensation control algorithms
TANG Gang,HU Chao,YAO Xiaoqiang,LI Jianxia,HAN Chongyang,SHAO Chentong,HU Xiong
In order to compensate the ship's motion response in waves and improve the efficiency of marine operation, more advanced motion control technologies were needed for wave compensation equipment. And for better understanding the wave compensation control technology development, the classification methods of feedforward control and feedback control were adopted to introduce the wave compensation control algorithm research status. Among them, the main algorithms of feedforward control are Kalman filtering method, neural network, and time series analysis method; the main algorithms of feedback control are PID control algorithm and model predictive control algorithm. The theory and research states of these algorithms in wave compensation control were analyzed and the key characteristics of Kalman filtering method, neural network, time series analysis method, PID control algorithm, and model predictive control algorithm through the comparative analysis of the related academic literaturef were pointed out. In the conclusion, according to the principles and characteristics of diffe-rent control algorithms, the algorithm of the next possible research direction in the wave compensation control is given which provides guidance to the research and development of wave compensation control system.

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2021 Vol. 39 (6): 576-582 [Abstract] ( 41 ) [HTML 1KB] [ PDF 1667KB] ( 435 )
583 Optimization of PID parameters of hydraulic turbine governing system based on SOA
GU Zhi,ZENG Yun*,LI Min,WU Yifan,HOU Rui,Qian Jing
In view of the existing optimization methods that were complex and easy to fall into local optimum, a method optimizing proportional-integral-differential control parameter based on seeker optimization algorithm was proposed for hydraulic turbine governing system. In order to verify the feasibility of the algorithm, a nonlinear model of hydraulic turbine governing system was established, and the integrated time absolute error of the rotational speed error in the hydraulic turbine generating set was used as the objective function of the optimization algorithm. In order to verify the effectiveness of the optimization results, the control effect of seeker optimization algorithm was compared with that of particle swarm optimization in the references. The simulation results show that under 5% frequency disturbance, seeker optimization algorithm has converged since the 29th iteration, and the system optimized by seeker optimization algorithm can be stable within 8 seconds, and the system overshoot is 1.6% at this time; under 10% load disturbance, seeker optimization algorithm has converged since the 25th iteration. The optimization effect of seeker optimization algorithm is basically the same as that of particle swarm optimization. Both stabilize the system within 10 seconds, but that by the seeker optimization algorithm is smaller than by the particle swarm optimization, which indicates that seeker optimization algorithm has a better search function and can partly improve the dynamic performance of the unit under isolated operating conditions.
2021 Vol. 39 (6): 583-588 [Abstract] ( 28 ) [HTML 1KB] [ PDF 1786KB] ( 269 )
589 Characteristic analysis and structural parameter optimization of solid-phase concentration capacitive sensor
HU Guoqiang,ZHANG Xiliang，XU Yunfeng,
Aiming at the problem that the solid phase material concentration detection in the spiral feeding pipeline is greatly affected by the solid phase distribution,based on the capacitance detection principle, a spiral surface plate capacitance sensor was designed. The finite element simulation method was used to establish a three-dimensional finite element model of the capacitance sensor,and the sensitivity distribution characteristic of the capacitance sensor was simulated and analyzed.The influence of structural parameters such as source/detection plate angle, plate axial length, shield radius and protection plate angle on the indexes of the field of the capacitance sensor was analyzed. Using the single factor rotation method, the ideal level range of each factor was obtained. In order to reduce the uniformity error, the orthogonal experiment and variance analysis method were selected to obtain the priority of each factor and the optimal combination of factors, and the sensitivity field uniformity error parameter is 5.06%. The uniformity verification test of detection field was designed, and the sensor was built. The measured sensitivity field uniformity error parameter is 5.43%, which significantly improves the soft field effect of the sensor detection field, reduces the influence of the solid phase distribution on the detection of the solid phase concentration, and meets the needs of practical applications.

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2021 Vol. 39 (6): 589-595 [Abstract] ( 19 ) [HTML 1KB] [ PDF 17018KB] ( 250 )
596 Experimental research on aerodynamic performance and generation performance for small horizontal axis wind turbine
ZAN Binghe,HE Miao,ZHU Jianyong*,LI Guowen
In order to reveal the difference between aerodynamic performance and generation perfor-mance for a small wind turbine, the aerodynamic performance of a novel wind rotor and the generation performance of the alternator driven by the same rotor are tested in a low-speed wind tunnel, the aerodynamic characteristics and electromagnetic property are analyzed in depth. Based on aerodynamic power data and generation power data, the optimal operating curve and the actual operating curve are plotted under different wind speeds, showing that the generation power and the corresponding rotation speed are both less than the aerodynamic power and the corresponding rotation speed. The aerodynamic torque first increases, then decreases with rotation speed, while the electromagnetic torque increases continuously with rotation speed. When the increased electromagnetic torque approaches the decreased aerodynamic torque, the alternator rotation speed cannot reach that of aerodynamic power peak, the mismatch between aerodynamic torque and electromagnetic torque is the main reason for the perfor-mance difference. Besides, the experimental data benefit the research on the maximum power tracking control strategy of the wind turbine.
2021 Vol. 39 (6): 596-601 [Abstract] ( 22 ) [HTML 1KB] [ PDF 3851KB] ( 397 )
602 Identification method of cotton seedlings and weeds in Xinjiang based on Faster R-CNN
XU Yan,WEN Desheng,ZHOU Jianping*,FAN Xiangpeng,LIU Yang
Aiming at the problems of over-fitting and low accuracy caused by the accompanying cha-racteristics of weeds in cotton fields in Xinjiang, taking cotton seedlings and weeds in Xinjiang as research objects, the factors affecting the low recognition rate of weeds were analyzed, and a network recognition model based on Faster R-CNN was established. A total of 5 370 cotton seedlings and weeds were collected from different angles and different natural environments and different intensive levels. In order to ensure sample quality and diversity, color migration and data enhancement were used to improve the color characteristics of the image and to expand the sample size, and the network model training was performed in the PASCAL VOC format data set. By comprehensively comparing the recognition time and accuracy of the four networks VGG16, VGG19, ResNet50 and ResNet101, the VGG16 network training Faster R-CNN model was selected. On this basis, the optimal anchor scale with aspect ratio of 1∶1 was designed. Under this model, Xinjiang cotton seedlings and weeds were identified, and the average recognition accuracy of 91.49% was achieved. The average recognition time was 262 ms. It provides a reference for the development of agricultural intelligent precision weeding equipment.
2021 Vol. 39 (6): 602-607 [Abstract] ( 40 ) [HTML 1KB] [ PDF 17871KB] ( 353 )
608 Scenarios analysis of field waterlogging in Lixiahe Plain, Jiangsu Province —case study of a typical polder in Gaoyou Irrigation District
MI Boyu,CHEN Haorui*,JIN Yinlong,WANG Shaoli,LI Jiang′an,SUN Yong
In order to analyze the changing characteristics offield waterlogging in the Lixiahe Plain in Jiangsu Province after environmental changes, taking a typical polder in Gaoyou Irrigation District as an example, the waterlogging distribution and production reduction were simulated with a distributed model of field waterlogging under varying conditions of environmental factors such as rainstorm intensity, bucket scale, efflux conditions, pumping capacity, and pumping station scheduling rules, etc. The results show that under current conditions, the area affected by waterlogging in the study area will be 10.47% when 5% rainstorm is encountered, with 4.07% maximum yield reduction rate. However, when 2% and 1% rainstorms are encountered, the ratio of waterlogged area increases to 56.54% and 86.87%, and the maximum yield reduction rate increases to 10.32% and 13.37%. If the depth of the bucket ditch is dug from the current 1.3 m to 2.0 m, the area affected by 5%, 2%, and 1% rainstorm conditions can be reduced by 14.73%, 16.11%, and 3.91%, and the maximum yield reduction rate can be reduced by 5.16%, 4.75%, and 3.81%. If the water level of the outer river is pre-dropped by 0.5 m, the area affected by 5%, 2%, and 1% rainstorm conditions can be reduced by 86.87%, 13.62%, and 8.52%, and the maximum yield reduction rate can be reduced by 66.59%, 40.60%, and 28.12%. If the efflux capacity of the pumping station in the study area is increased from the current 9 m3/s to 14 m3/s, the situation remains unchanged when 5% rainstorm is encountered, while under 2% and 1% rainstorm conditions, the affected area can be reduced by 31.68% and 11.52%, and the maximum yield reduction rate can be reduced by 31.10% and 11.44%. Decreasing the drainage level valve of the pumping station without lowering the warning water level of the outer river has almost no impact on the flood mitigation effect.

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2021 Vol. 39 (6): 608-614 [Abstract] ( 22 ) [HTML 1KB] [ PDF 5216KB] ( 392 )
615 Optimizating of depth of drippers for layered subsurface drip irrigation of grapes
DU Yichao,CAI Yaohui*,ZHANG Lin,ZHU Delan,ZHANG Guangdi,LI Yuding,JIA Yinan,WU Yong
It is difficult for the subsurface drip irrigation wetting body to better match the root system water absorption at different growth stages. In order to solve the problem, some researchers have proposed a new type of subsurface drip irrigation, layered subsurface drip irrigation system. A combination of laboratory experiments and HYDRUS-2D numerical simulation was used, the two major grape-producing areas in Ningxia and Guanzhong were taken as examples to study the soil water movement law of layered subsurface drip irrigation, and the layered subsurface drip irrigation optimal placement depth was proposed. The research results show that the simulated value of HYDRUS-2D has a good agreement with the measured value. The depth of the drippers directly affects the distribution of soil moisture, and the soil volume within the optimal water content range under two types of soil increases with the increase of the distance between drippers. Appropriately increasing the depth of the shallow dripper and reducing the depth of the deep dripper can reduce the inefficient loss of water. In order to avoid inefficient consumption of water and improve the matching effect of wetting body and root system, it is recommended that the appropriate depth placement with a single dripper of grapes in Guanzhong area is 20 cm. The depth of dripper placement in Ningxia are preferably 15 cm and 45 cm.

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2021 Vol. 39 (6): 615-621 [Abstract] ( 27 ) [HTML 1KB] [ PDF 6332KB] ( 305 )
622 Estimation of chlorophyll content of summer maize canopy based on UAV multispectral remote sensing
CHEN Hao,FENG Hao*,YANG Zhenting,WANG Naijiang,LI Yue,WANG Qingsong,
The remote sensing of unmanned aerial vehicle(UAV)has the advantages of monitoring crop nutritional status accurately and flexibly. Modeling crop canopy chlorophyll content is of great significance for efficient agricultural management. In the present study, the multispectral remote sensing data of UAV at different levels of nitrogen fertilizer rate were used to estimate the chlorophyll content of summer maize canopy in 2019. Firstly, 10 spectral vegetation indexes were selected to determine the vegetation indices that were significantly related to the chlorophyll content of summer maize canopy. Secondly, the estimation models of chlorophyll content were established by linear regression and stepwise regression analyses. The results showed that the chlorophyll content of summer maize canopy increased first and then decreased with the nitrogen fertilizer rate increasing. There is no significant difference in chlorophyll content between different topdressing treatments at the same level of nitrogen fertilizer rate. 9 out of 10 spectral vegetation indexes were significantly correlated with chlorophyll content, especially GNDVI whose correlation coefficient with chlorophyll content was the highest and reached 0.892. In comparison with linear regression models, the stepwise regression model showed the best performance in modeling chlorophyll content with coefficient of determination of 0.87, root mean square error of 0.15, and relative error of 2.68%. Therefore, the real-time monitoring of chlorophyll content for summer maize canopy can be achieved by UAV multispectral remote sensing combined with stepwise regression model at the field scale.

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2021 Vol. 39 (6): 622-629 [Abstract] ( 38 ) [HTML 1KB] [ PDF 10329KB] ( 216 )
630 Application of UAV radar to survey of ice thickness and ice structure
LIU Hui,JI Honglan,LUO Hongchun,GAO Guoming,ZHANG Baosen,MOU Xianyou*
In order to improve the measurement efficiency of ice thickness in the Yellow River, the UAV radar was used to detect the ice thickness in the Shisifenzi bend of the Yellow River in Inner Mongolia, the results were compared with the measured ice thickness, and the characteristics of the typical radar images of the ice layer were analyzed as well. The results showed that the ice thickness of the Shensifenzi bend was uneven, the ice thickness was between 40 and 80 cm, overall, longitudinally, the ice thickness decreased, the minimum thickness was located at the apex of the bend, the ice thickness on the concave bank was larger than that on the convex bank, the ice thickness of open water area presented a small-large-small trend, and the ice thickness near the water surface was smallest. For the measurement effect, the vertical frozen area was general, the result of radar measurement was greater than that of manual measurement, the error was about 10%, the flat frozen ice sheet was fine, and the error was less than 5%. The radar measurement results and the manual measurement results had a strong consistency on the trend of the ice thickness, and the propagation velocity of radar wave in the ice layer was between 15—17 cm /ns. Radar images could reflect the structure, position and direction of the ice cracks in ice layer, and the radar images of flat frozen ice sheet and vertical frozen ice sheet were quite different. The UAV radar can measure the ice thickness quickly, which greatly improves the test efficiency of ice thickness in small areas.It provides a technical reference for the analysis of the freezing-thawing process of the ice and the structure under the ice in the Yellow River, which is an ideal method for ice detection.
2021 Vol. 39 (6): 630-636 [Abstract] ( 22 ) [HTML 1KB] [ PDF 18171KB] ( 249 )
637 Relationship between solar energy and sprinkler hydraulic performance of solar sprinkler irrigation system
LIU Junping*,XU Jien,LI Tao,ZAMAN Muhammad
Facing the shortage of energy and the limitation of water resources, the development of agricultural irrigation has been constrained, especially in some remote areas where the maximum electricity cannot be fully guaranteed. The solar sprinkler irrigation system can save energy and water. It can greatly improve the efficiency of farmland irrigation, reduce labor costs, and solve the problem of irrigation power in the areas where electricity power is in shortage. However, the hydraulic performance of solar sprinkler irrigation system, which are put into use currently, is poor, limiting the development of solar sprinkler irrigation system. In order to solve the problem that the hydraulic performance can not be effectively predicted in the application of solar sprinkler irrigation system, summer experiments on the hydraulic performance of the solar sprinkler irrigation system under typical weather were carried out, taking the solar energy intensity as the influencing factor, and taking the pump outlet flow rate, pump outlet pressure, sprinkler wet radius, water distribution and irrigation uniformity coefficient of the system as the evaluation index, to find which is the better data of the solar energy intensity. The change rule of spraying hydraulic performance under solar energy intensity was obtained, and the solar energy intensity data needed under the optimum working condition of the system was obtained. The experimental results show that system flow rate and pump outlet pressure increase with the increase of solar energy intensity, and the variation of pump flow rate and pressure with solar energy intensity basically conforms to the exponential distribution law. When the solar energy intensity is more than 800.0 W/m2, the system flow rate is about 1.82 m3/h, and remain unchanged, pump outlet pressure at the same time is stable at 0.43-0.44 MPa. The sprinkler wet radius generally showed a slight upward trend which between is 8.9 m and 9.7 m with the increase of solar energy intensity. When the solar energy intensity is more than 900.0 W/m2, the sprinkler wet radius fluctuates to a certain extent and keeps at about 9.2 m. When the solar energy intensity is more than 200.0 W/m2, the wet radius tends to be stable. The curve shape of water distribution tends to flatten gradually from triangle with the increase of solar energy intensity. When the average solar energy intensity is about 225.7 W/m2, the curve shape of water distribution tends to be trapezoidal. When the solar energy intensity is more than 900.0 W/m2, the curve shape of water distribution remained basically unchanged. The function relationship between average solar energy intensity and uniformity coefficient was obtained. When the solar energy intensity is more than 900.0 W/m2, the uniformity coefficient CU of sprinkler irrigation system is more than 88%. When the solar energy intensity is between 200.0 W/m2 and 600.0 W/m2, the uniformity coefficient of sprinkler irrigation is between 76% and 82%. The solar sprinkler irrigation system can work normally when the solar energy intensity is above 200.0 W/m2. This study can provide references for realizing the combination of solar energy and agricultural machinery, improving hydraulic perfor-mance of solar sprinkler irrigation system, promoting the popularization and application of solar sprinkler irrigation system in practical projects and solving the problem of irrigation power shortage in the areas with less electricity energy.
2021 Vol. 39 (6): 637-642 [Abstract] ( 32 ) [HTML 1KB] [ PDF 3596KB] ( 362 )
643 Experimental study on mechanical properties of red Pisha-sandstone cement soil under freeze-thaw cycles
GENG Kaiqiang,LI Xiaoli*
In order to realize the potential utilization value of Pisha-sandstone as a natural resource, the effective utilization of Pisha-sandstone is improved. The red Pisha-sandstone in Zhungeer banner of Ordos City is added with different cement contents to produce the Pisha-sandstone cement soil,and the unconsolidated undrained triaxial tests under different cement mixing ratios, confining pressures and freeze-thaw cycles were carried out. The variation regularities of mechanical parameters of Pisha-sandstone cement soil were obtained, and the meso-structure of Pisha-sandstone cement soil was observed through ultra-depth three-dimensional microscope. The results show that the stress-strain curve of Pisha-sandstone cement soil presents a strain softening trend. The cohesive force and internal friction angle increase linearly with the increase of cement content. The internal friction angle of Pisha-sandstone cement soil is less affected by freeze-thaw cycles, while the cohesion is more affected by freeze-thaw cycles. The more cement content, the better the frost resistance, but the more obvious its brittleness. The meso-structure observation further verifies that the freeze-thaw cycle cause a large change in the meso-structure of cement soil with a small amount of addition, and the increased internal voids can be observed. With the increase of cement content, the compactness of cement soil structure is increased, and the frost resistance of cement soil is effectively improved.
2021 Vol. 39 (6): 643-648 [Abstract] ( 22 ) [HTML 1KB] [ PDF 8299KB] ( 302 )
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