Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under...Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under the dynamic train load of a high-speed railway is not yet understood.In light of this,a heavily instrumented piled embankment model was set up,and a model test was carried out,in which a servo-hydraulic actuator outputting M-shaped waves was adopted to simulate the process of a running train.Earth pressure,settlement,strain in the geogrid and pile and excess pore water pressure were measured.The results show that the soil arching height under the dynamic train load of a high-speed railway is shorter than under static loading.The growth trend for accumulated settlement slowed down after long-term vibration although there was still a tendency for it to increase.Accumulated geogrid strain has an increasing tendency after long-term vibration.The closer the embankment edge,the greater the geogrid strain over the subsoil.Strains in the pile were smaller under dynamic train loads,and their distribution was different from that under static loading.At the same elevation,excess pore water pressure under the track slab was greater than that under the embankment shoulder.展开更多
A series of small-scale 1g X-section cast-in-place concrete(XCC)pile-penetration model tests were conducted to study the effects of soil density and pile geometry on the lateral responses of an existing pile and the v...A series of small-scale 1g X-section cast-in-place concrete(XCC)pile-penetration model tests were conducted to study the effects of soil density and pile geometry on the lateral responses of an existing pile and the variations in surrounding soil stress.The results showed that the bending patterns of existing XCC piles varied with penetration depth.The lateral response of the existing pile was sensitive to the change in relative density and pile geometry.For example,the bending moment of the existing pile increased along with these parameters.The development of the radial stressσ′r/σ′v0 of the soil around an existing pile showed different trends at various depths during the penetration of the adjacent pile.Moreover,the change in radial stress during the penetration of the XCC pile did not exhibit the“h/R effect”that was observed in the free-field soil,due to the shielding effect of the existing piles.The peak value of radial stressσ′r_max/σ′v0 decreased exponentially as the radial distance r/R increased.The attenuation ofσ′r_max/σ′v0 with r/R in the loose sand was faster than in the medium-dense or dense sands.Theσ′r_max/σ′v0 at the same soil location increased with the cross-section geometry parameter.展开更多
The p H plays a key role in the growth and colonization of plant pathogens as well as the onset and progression of the symptoms they cause within the host.Plants may quickly alter their apoplastic p H(pH_(apo))to prot...The p H plays a key role in the growth and colonization of plant pathogens as well as the onset and progression of the symptoms they cause within the host.Plants may quickly alter their apoplastic p H(pH_(apo))to protect themselves against infection.However,pathogens can also alter the p H of their ambient environment to promote their own growth.Citrus canker is a serious plant disease caused by Xanthomonas citri subsp.citri(Xcc).This Gram-negative aerobic rod is usually cultured in Luria-Bertani(LB)medium at p H 7.However,little is known about the changes in p H both in this medium as Xcc grows and in the leaf apoplast in response to Xcc infection and colonization.Moreover,the differences in leaf apoplast p H between Xcc-resistant and Xcc-susceptible citrus genotypes are also unknown.Here,Xcc grew well in liquid LB medium at initial p H6-8 and the pathogen altered the medium p H to 6.8±0.4.Xcc growth declined at p H 5 and was zero at p H 3,4,9,and 10.In susceptible sweet orange infected with Xcc inoculum,canker symptoms were inhibited at p H 3,4,and 10 but did not differ in the range of p H 5-9.As expected,canker symptoms were absent at all inoculum p H in the resistant Citron C-05.For both genotypes,Xcc only grew well in the leaves exposed to p H 5-8 inoculums.At four days post-inoculation(4 dpi),the foliar pH_(apo)of resistant Citron C-05 had rapidly declined from 5.6 to 4.4.At 2 dpi,the p Hapoof susceptible sweet orange had rapidly increased from 5.6 to 6.7,Xcc grew quickly,and canker symptoms appeared.Plasma membrane(PM)H^(+)-ATPase activation with fusicoccin(FC)acidified the apoplast and upregulated the pathogenesis-related genes(PRs)in the sweet orange leaves.Hence,Xcc colonization and canker development were inhibited.The results of this study revealed that apoplastic acidification is implicated in the resistance of Citron C-05 to Xcc infection and provided insight into the association between pH_(apo)regulation and resistance to bacterial pathogen invasion in plants.展开更多
基金National Natural Science Foundation of China under Grant Nos.51622803,51378177 and 51420105013the 111 Project under Grant No.B13024
文摘Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under the dynamic train load of a high-speed railway is not yet understood.In light of this,a heavily instrumented piled embankment model was set up,and a model test was carried out,in which a servo-hydraulic actuator outputting M-shaped waves was adopted to simulate the process of a running train.Earth pressure,settlement,strain in the geogrid and pile and excess pore water pressure were measured.The results show that the soil arching height under the dynamic train load of a high-speed railway is shorter than under static loading.The growth trend for accumulated settlement slowed down after long-term vibration although there was still a tendency for it to increase.Accumulated geogrid strain has an increasing tendency after long-term vibration.The closer the embankment edge,the greater the geogrid strain over the subsoil.Strains in the pile were smaller under dynamic train loads,and their distribution was different from that under static loading.At the same elevation,excess pore water pressure under the track slab was greater than that under the embankment shoulder.
基金supported by the National Natural Science Foundation of China(Nos.52308352,52238009,and 52108321)the Jiangxi Provincial Natural Science Foundation of China(No.20232BAB214082)+1 种基金the Open Research Fund Program of Guangdong Key Laboratory of Earthquake Engineering and Application Technology(No.2020B1212060071)the Science&Technology Project of the Education Department of Jiangxi Province(No.GJJ2200681),China.
文摘A series of small-scale 1g X-section cast-in-place concrete(XCC)pile-penetration model tests were conducted to study the effects of soil density and pile geometry on the lateral responses of an existing pile and the variations in surrounding soil stress.The results showed that the bending patterns of existing XCC piles varied with penetration depth.The lateral response of the existing pile was sensitive to the change in relative density and pile geometry.For example,the bending moment of the existing pile increased along with these parameters.The development of the radial stressσ′r/σ′v0 of the soil around an existing pile showed different trends at various depths during the penetration of the adjacent pile.Moreover,the change in radial stress during the penetration of the XCC pile did not exhibit the“h/R effect”that was observed in the free-field soil,due to the shielding effect of the existing piles.The peak value of radial stressσ′r_max/σ′v0 decreased exponentially as the radial distance r/R increased.The attenuation ofσ′r_max/σ′v0 with r/R in the loose sand was faster than in the medium-dense or dense sands.Theσ′r_max/σ′v0 at the same soil location increased with the cross-section geometry parameter.
基金supported by grants from the Provincial Special Project of the Research and Demonstration of High-Efficiency Breeding Technology for Citrus,China(Grant No.2024sfq02)Postgraduate Scientific Research Innovation Project of Hunan Province,China(Grant No.CX20210671).
文摘The p H plays a key role in the growth and colonization of plant pathogens as well as the onset and progression of the symptoms they cause within the host.Plants may quickly alter their apoplastic p H(pH_(apo))to protect themselves against infection.However,pathogens can also alter the p H of their ambient environment to promote their own growth.Citrus canker is a serious plant disease caused by Xanthomonas citri subsp.citri(Xcc).This Gram-negative aerobic rod is usually cultured in Luria-Bertani(LB)medium at p H 7.However,little is known about the changes in p H both in this medium as Xcc grows and in the leaf apoplast in response to Xcc infection and colonization.Moreover,the differences in leaf apoplast p H between Xcc-resistant and Xcc-susceptible citrus genotypes are also unknown.Here,Xcc grew well in liquid LB medium at initial p H6-8 and the pathogen altered the medium p H to 6.8±0.4.Xcc growth declined at p H 5 and was zero at p H 3,4,9,and 10.In susceptible sweet orange infected with Xcc inoculum,canker symptoms were inhibited at p H 3,4,and 10 but did not differ in the range of p H 5-9.As expected,canker symptoms were absent at all inoculum p H in the resistant Citron C-05.For both genotypes,Xcc only grew well in the leaves exposed to p H 5-8 inoculums.At four days post-inoculation(4 dpi),the foliar pH_(apo)of resistant Citron C-05 had rapidly declined from 5.6 to 4.4.At 2 dpi,the p Hapoof susceptible sweet orange had rapidly increased from 5.6 to 6.7,Xcc grew quickly,and canker symptoms appeared.Plasma membrane(PM)H^(+)-ATPase activation with fusicoccin(FC)acidified the apoplast and upregulated the pathogenesis-related genes(PRs)in the sweet orange leaves.Hence,Xcc colonization and canker development were inhibited.The results of this study revealed that apoplastic acidification is implicated in the resistance of Citron C-05 to Xcc infection and provided insight into the association between pH_(apo)regulation and resistance to bacterial pathogen invasion in plants.
