Repeated wet swelling and dry shrinkage of soil leads to the gradual occurrence of cracks and the formation of a complex fracture network.In order to study the development characteristics and quantitative analysis of ...Repeated wet swelling and dry shrinkage of soil leads to the gradual occurrence of cracks and the formation of a complex fracture network.In order to study the development characteristics and quantitative analysis of cracks in root-soil complex in different growth periods under dry-wet cycles,the alfalfa root-loess complex was in-vestigated during different growth periods under different dry-wet cycles,and a dry-wet cycle experiment was conducted.The crack rate,relative area,average width,total length,and the cracks fractal dimension in the root-soil complex were extracted;the crack development characteristics of plain soil were analyzed under the PG-DwC(dry-wet cycle caused by plant water management during plant growth period),as well as the crack development characteristics of root-soil complex under PG-DWC and EC-DWC(the dry-wet cycles caused by extreme natural conditions such as continuous rain);the effects of plant roots and dry-wet cycles on soil cracks were discussed.The results showed that the average crack width,crack rate,relative crack area,and total crack length of the alfalfa root-loess complex were higher than those of the plain soil during PG-DWC.The result indicated that compared with plain soil during PG-DWC,the presence of plant roots in alfalfa root-soil complex in the same growth period promoted the cracks development to some extent.The alfalfa root-soil complex crack parameters during different growth periods were relatively stable during PG-DWC(O dry-wet cycle).During EC-DWC(1,3,and 5 dry-wet cycles),the alfalfa root-loess complex crack parameters increased with the number of dry-wet cycles during different growth periods.Unlike PG-DWC,the EC-DWC accelerated crack development,and the degree of crack development increased with the number of dry-wet cycles.The existence of plant roots promoted crack development and expansion in the root-soil complex to a certain extent,and the dry-wet cycle certainly promoted crack development and expansion in the root-soil complex.This result contradicts the im-provement in the root-soil complex's macro-mechanical properties during plant growth,due to differences in the mechanical properties of roots and soil.The research results will provide reference for the root soil complex crack development law and the design of slope protection by vegetation.展开更多
Triaxial compression tests were conducted on the alfalfa root-loess complex at different growthperiods obtained through artificial planting.The research focused on analyzing the time variation law of the shear strengt...Triaxial compression tests were conducted on the alfalfa root-loess complex at different growthperiods obtained through artificial planting.The research focused on analyzing the time variation law of the shear strength index and deformation index of the alfalfa root-loess complex under dry-wet cycles.Additionally,the time effect of the shear strength index of the alfalfa root-loess complex under dry-wet cycles was analyzed and its prediction model was proposed.The results show that the PG-DWC(dry-wet cycle caused by plant water management during plant growth period)causes the peak strength of plain soil to change in a"V"shape with the increase of growth period,and the peak strength of alfalfa root-loess complex is higher than that of plain soil at the same growth period.The deterioration of the peak strength of alfalfa root-loess complex in the same growth period is aggravated with the increase of drying and wetting cycles.Compared with the 0 days growth period,the effective cohesion of alfalfa root-loess complex under different dry-wet cycles maximum increase rate is at the 180 days,which are 33.88%,46.05%,30.12%and 216.02%,respectively.When the number of dry-wet cycles is constant,the effective cohesion of the alfalfa root-loess complex overall increases with the growth period.However,it gradually decreases comparedwith the previous growth period,and the minimum increase rate are all at the 180 days.For the same growth period,the effective cohesion of the alfalfa root-loess complex decreases with the increase of the number of dry-wet cycles.This indicates that EC-DWC(the dry-wet cycles caused by extreme natural conditions such as continuous rain)have a detrimental effect on the time effect of the shear strength of the alfalfa root-loess complex.Finally,based on the formula of total deterioration,a prediction model for the shear strength of the alfalfa root-loess complex under dry-wet cycles was proposed,which exhibits high prediction accuracy.The research results provide useful guidance for the understanding of mechanical behavior and structural damage evolution of root-soil composite.展开更多
The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,E...The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,Eleusine indica,Potentilla anserine,and Artemisia argyi,according to the classification in Botany,and the thrust-displacement curves and failure patterns of different samples were analysed by comparison to fill the aforementioned gap.Results reveal that the roots can reduce the characteristics of soil brittleness and enhance its capability to resist large deformation,and different root types contribute different effects to the strain-hardening behavior of the root-soil mass.The contribution of the fibrous root system to strength is limited,whilst the tap root system substantially enhances strength and stiffness.Results of failure patterns show that fibrous and tap root systems affect soil solidification and surface cracking reduction.However,the effect of the tap root system depends on the composition of lateral and tap roots:long and rich lateral roots are effective for resisting the creation of cracks,but thick tap roots with few and thin lateral roots may lead to several surface cracks.展开更多
To solve the problem of soil loosening caused by whole plant vibration during the operation of a vibrating blueberry harvester,the force model of the blueberry tree containing root soil was established and analyzed.Th...To solve the problem of soil loosening caused by whole plant vibration during the operation of a vibrating blueberry harvester,the force model of the blueberry tree containing root soil was established and analyzed.The main factors affecting the impact force of the shaker were the curvature of the shaker,the branch curvature,and the equivalent elastic modulus at the impact point.Through the analysis of the transfer law of vibration between the exciting force and the root-soil complex,it is concluded that the shear strength decreases with the decrease of the internal friction angle,resulting in loose soil and easy toppling of the fruit trees.Discrete element simulation was used to analyze the force of the blueberry model.The results showed that the lower the excitation height,the more drastic the fluctuation of the root-soil complex.In the range of excitation height from 200 mm to 500 mm,soil acceleration increased by 45.5%on average for every 150 mm decrease.From 200 mm to 50 mm,the average soil acceleration increased by 69.1%.Finally,through the field excitation sensor test,the sensor was buried in 200 mm,100 mm,and 0 mm(that is,placed on the surface)of soil,and the exciting force was applied to blueberry branches at heights of 50 mm,200 mm,350 mm,and 500 mm,respectively,for four times,and then the soil acceleration was output.A total of 48 sets of experimental data were obtained.By combining the scattering data obtained from the experiment with the simulated curve,it can be analyzed that when the excitation heights were 50 mm and 500 mm,the soil fluctuation at the depth of 100 mm was close to the simulated average value.When the excitation heights were 200 mm and 350 mm,the fluctuation of surface soil with a depth of 0 mm was close to the simulated average value.When the excitation height was 500 mm,the root-soil complex fluctuated twice due to the obvious reciprocating swing of the fruit tree.Since very little vibration energy was consumed during transmission,the vibration was strongest in the surface soil.Soil with a depth of 200 mm was almost unaffected by the excitation force and excitation height because too much vibration energy was consumed during transmission.The results show that the established model and simulation scheme are reliable and can provide a theoretical basis for the optimization of the incentive parameters of blueberry fruit trees.展开更多
The calcareous fluvo-aquic soil was collected and a microcosm study was carried out with root-mat and frozenslicing method in laboratory. The pH in the root-soil interface with the control treatment was just slightly ...The calcareous fluvo-aquic soil was collected and a microcosm study was carried out with root-mat and frozenslicing method in laboratory. The pH in the root-soil interface with the control treatment was just slightly lower than in the bulk soil.However,the addition of NH<sub>4</sub><sup>-</sup> -N significantly decreased the pH value in the root-soil interface and the addition of No<sub>3</sub> -N slightly increased the pH value in the root-soil interface.The magnitude of pH changes in the root-soil interface depended upon the concentrations of the nitrogen sources added.The contents of Ca<sub>2</sub>-P,Fe-P and Al-P in the root-soil interface were much lower after treated with NH<sub>4</sub> -N and slightly higher after treated with No<sub>3</sub> -N compared with control treatment.After treated with 100,200 and 400 mg·kg<sup>-1</sup>NH<sub>4</sub><sup>+</sup> -N,the deficiency rates of Ca<sub>2</sub>-P in the area 0-1 mm from the root plane were 37.1%,45.9%and 57.7%,respectively,the deficiency rates of Fe-P were 23.4%,29.1%and 38.2%,respectively,and the deficiency rates of Al-P were 25.1%,28.0%and 33.2%,respectively. Compared with the control the deficiency rates of Ca<sub>8</sub>-P in NH<sub>4</sub><sup>+</sup> -N and No<sub>3</sub>-N treatments decreased and increased,respectively,but the differences were not obvious.The contents of Ca<sub>10</sub> -P and O-P in the root-soil interface did not significantly change after treated with NH<sub>4</sub><sup>+</sup> -N or No<sub>3</sub> -N,suggesting that Ca<sub>10</sub>- P and O-P were remarkably difficult to be mobilized even at the presence of high concentration of NH<sub>4</sub><sup>+</sup> -N.The lowered pH in the root-soil interface induced by the addition of the NH<sub>4</sub> -N promoted the transformation of phosphates in the root-soil interface,enhanced the mobilization and bioavailability of phosphates,and thereby remarkably increased the absorption of phosphorus by roots.展开更多
基金the Key Research and Development Project of Ningxia Hui Autonomous Region(No.2023BEG02072)for their financial support.
文摘Repeated wet swelling and dry shrinkage of soil leads to the gradual occurrence of cracks and the formation of a complex fracture network.In order to study the development characteristics and quantitative analysis of cracks in root-soil complex in different growth periods under dry-wet cycles,the alfalfa root-loess complex was in-vestigated during different growth periods under different dry-wet cycles,and a dry-wet cycle experiment was conducted.The crack rate,relative area,average width,total length,and the cracks fractal dimension in the root-soil complex were extracted;the crack development characteristics of plain soil were analyzed under the PG-DwC(dry-wet cycle caused by plant water management during plant growth period),as well as the crack development characteristics of root-soil complex under PG-DWC and EC-DWC(the dry-wet cycles caused by extreme natural conditions such as continuous rain);the effects of plant roots and dry-wet cycles on soil cracks were discussed.The results showed that the average crack width,crack rate,relative crack area,and total crack length of the alfalfa root-loess complex were higher than those of the plain soil during PG-DWC.The result indicated that compared with plain soil during PG-DWC,the presence of plant roots in alfalfa root-soil complex in the same growth period promoted the cracks development to some extent.The alfalfa root-soil complex crack parameters during different growth periods were relatively stable during PG-DWC(O dry-wet cycle).During EC-DWC(1,3,and 5 dry-wet cycles),the alfalfa root-loess complex crack parameters increased with the number of dry-wet cycles during different growth periods.Unlike PG-DWC,the EC-DWC accelerated crack development,and the degree of crack development increased with the number of dry-wet cycles.The existence of plant roots promoted crack development and expansion in the root-soil complex to a certain extent,and the dry-wet cycle certainly promoted crack development and expansion in the root-soil complex.This result contradicts the im-provement in the root-soil complex's macro-mechanical properties during plant growth,due to differences in the mechanical properties of roots and soil.The research results will provide reference for the root soil complex crack development law and the design of slope protection by vegetation.
基金received the Key Research and Development Project of Ningxia Hui Autonomous Region(2022BEG03052,2023BEG02072).
文摘Triaxial compression tests were conducted on the alfalfa root-loess complex at different growthperiods obtained through artificial planting.The research focused on analyzing the time variation law of the shear strength index and deformation index of the alfalfa root-loess complex under dry-wet cycles.Additionally,the time effect of the shear strength index of the alfalfa root-loess complex under dry-wet cycles was analyzed and its prediction model was proposed.The results show that the PG-DWC(dry-wet cycle caused by plant water management during plant growth period)causes the peak strength of plain soil to change in a"V"shape with the increase of growth period,and the peak strength of alfalfa root-loess complex is higher than that of plain soil at the same growth period.The deterioration of the peak strength of alfalfa root-loess complex in the same growth period is aggravated with the increase of drying and wetting cycles.Compared with the 0 days growth period,the effective cohesion of alfalfa root-loess complex under different dry-wet cycles maximum increase rate is at the 180 days,which are 33.88%,46.05%,30.12%and 216.02%,respectively.When the number of dry-wet cycles is constant,the effective cohesion of the alfalfa root-loess complex overall increases with the growth period.However,it gradually decreases comparedwith the previous growth period,and the minimum increase rate are all at the 180 days.For the same growth period,the effective cohesion of the alfalfa root-loess complex decreases with the increase of the number of dry-wet cycles.This indicates that EC-DWC(the dry-wet cycles caused by extreme natural conditions such as continuous rain)have a detrimental effect on the time effect of the shear strength of the alfalfa root-loess complex.Finally,based on the formula of total deterioration,a prediction model for the shear strength of the alfalfa root-loess complex under dry-wet cycles was proposed,which exhibits high prediction accuracy.The research results provide useful guidance for the understanding of mechanical behavior and structural damage evolution of root-soil composite.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23090402)the National Natural Science Foundation of China(Nos.41790442,41825018)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0904)。
文摘The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,Eleusine indica,Potentilla anserine,and Artemisia argyi,according to the classification in Botany,and the thrust-displacement curves and failure patterns of different samples were analysed by comparison to fill the aforementioned gap.Results reveal that the roots can reduce the characteristics of soil brittleness and enhance its capability to resist large deformation,and different root types contribute different effects to the strain-hardening behavior of the root-soil mass.The contribution of the fibrous root system to strength is limited,whilst the tap root system substantially enhances strength and stiffness.Results of failure patterns show that fibrous and tap root systems affect soil solidification and surface cracking reduction.However,the effect of the tap root system depends on the composition of lateral and tap roots:long and rich lateral roots are effective for resisting the creation of cracks,but thick tap roots with few and thin lateral roots may lead to several surface cracks.
基金supported by Heilongjiang Provincial Discipline Collaborative Innovation Achievement Project(Grant No.LJGXCG2022-075)Postdoctoral Scientific Research Developmental Fund of Heilongjiang Province(LBH-Q21020).
文摘To solve the problem of soil loosening caused by whole plant vibration during the operation of a vibrating blueberry harvester,the force model of the blueberry tree containing root soil was established and analyzed.The main factors affecting the impact force of the shaker were the curvature of the shaker,the branch curvature,and the equivalent elastic modulus at the impact point.Through the analysis of the transfer law of vibration between the exciting force and the root-soil complex,it is concluded that the shear strength decreases with the decrease of the internal friction angle,resulting in loose soil and easy toppling of the fruit trees.Discrete element simulation was used to analyze the force of the blueberry model.The results showed that the lower the excitation height,the more drastic the fluctuation of the root-soil complex.In the range of excitation height from 200 mm to 500 mm,soil acceleration increased by 45.5%on average for every 150 mm decrease.From 200 mm to 50 mm,the average soil acceleration increased by 69.1%.Finally,through the field excitation sensor test,the sensor was buried in 200 mm,100 mm,and 0 mm(that is,placed on the surface)of soil,and the exciting force was applied to blueberry branches at heights of 50 mm,200 mm,350 mm,and 500 mm,respectively,for four times,and then the soil acceleration was output.A total of 48 sets of experimental data were obtained.By combining the scattering data obtained from the experiment with the simulated curve,it can be analyzed that when the excitation heights were 50 mm and 500 mm,the soil fluctuation at the depth of 100 mm was close to the simulated average value.When the excitation heights were 200 mm and 350 mm,the fluctuation of surface soil with a depth of 0 mm was close to the simulated average value.When the excitation height was 500 mm,the root-soil complex fluctuated twice due to the obvious reciprocating swing of the fruit tree.Since very little vibration energy was consumed during transmission,the vibration was strongest in the surface soil.Soil with a depth of 200 mm was almost unaffected by the excitation force and excitation height because too much vibration energy was consumed during transmission.The results show that the established model and simulation scheme are reliable and can provide a theoretical basis for the optimization of the incentive parameters of blueberry fruit trees.
文摘The calcareous fluvo-aquic soil was collected and a microcosm study was carried out with root-mat and frozenslicing method in laboratory. The pH in the root-soil interface with the control treatment was just slightly lower than in the bulk soil.However,the addition of NH<sub>4</sub><sup>-</sup> -N significantly decreased the pH value in the root-soil interface and the addition of No<sub>3</sub> -N slightly increased the pH value in the root-soil interface.The magnitude of pH changes in the root-soil interface depended upon the concentrations of the nitrogen sources added.The contents of Ca<sub>2</sub>-P,Fe-P and Al-P in the root-soil interface were much lower after treated with NH<sub>4</sub> -N and slightly higher after treated with No<sub>3</sub> -N compared with control treatment.After treated with 100,200 and 400 mg·kg<sup>-1</sup>NH<sub>4</sub><sup>+</sup> -N,the deficiency rates of Ca<sub>2</sub>-P in the area 0-1 mm from the root plane were 37.1%,45.9%and 57.7%,respectively,the deficiency rates of Fe-P were 23.4%,29.1%and 38.2%,respectively,and the deficiency rates of Al-P were 25.1%,28.0%and 33.2%,respectively. Compared with the control the deficiency rates of Ca<sub>8</sub>-P in NH<sub>4</sub><sup>+</sup> -N and No<sub>3</sub>-N treatments decreased and increased,respectively,but the differences were not obvious.The contents of Ca<sub>10</sub> -P and O-P in the root-soil interface did not significantly change after treated with NH<sub>4</sub><sup>+</sup> -N or No<sub>3</sub> -N,suggesting that Ca<sub>10</sub>- P and O-P were remarkably difficult to be mobilized even at the presence of high concentration of NH<sub>4</sub><sup>+</sup> -N.The lowered pH in the root-soil interface induced by the addition of the NH<sub>4</sub> -N promoted the transformation of phosphates in the root-soil interface,enhanced the mobilization and bioavailability of phosphates,and thereby remarkably increased the absorption of phosphorus by roots.
