It had been suggested to use the West African Compaction Test Procedure since the early 1950’s so as to determine the CBR of gravel lateritic soils in West African countries [1]. This test procedure called West Afric...It had been suggested to use the West African Compaction Test Procedure since the early 1950’s so as to determine the CBR of gravel lateritic soils in West African countries [1]. This test procedure called West African Compaction (WAC) [2] is largely used in road construction in West African countries and had the particularity to be long and use a large amount of material. This note is the result of several comparisons between test procedures taken to determine the CBR from the WAC method to the standardized laboratory test commonly used to determine the CBR.展开更多
The ultrasonic pulse velocity(UPV)correlates significantly with the density and pore size of subgrade filling materials.This research conducts numerous Proctor and UPV tests to examine how moisture and rock content af...The ultrasonic pulse velocity(UPV)correlates significantly with the density and pore size of subgrade filling materials.This research conducts numerous Proctor and UPV tests to examine how moisture and rock content affect compaction quality.The study measures the changes in UPV across dry density and compaction characteristics.The compacted specimens exhibit distinct microstructures and mechanical properties along the dry and wet sides of the compaction curve,primarily influenced by internal water molecules.The maximum dry density exhibits a positive correlation with the rock content,while the optimal moisture content demonstrates an inverse relationship.As the rock content increases,the relative error of UPV measurement rises.The UPV follows a hump-shaped pattern with the initial moisture content.Three intelligent models are established to forecast dry density.The measure of UPV and PSO-BP-NN model quickly assesses compaction quality.展开更多
While straw mulching has been recognized for mitigating compaction,the multifactorial effects of straw parameters(content,length,laying modes)under static versus dynamic loads remain poorly quantified.Straw mulching m...While straw mulching has been recognized for mitigating compaction,the multifactorial effects of straw parameters(content,length,laying modes)under static versus dynamic loads remain poorly quantified.Straw mulching may alter the stress transfer in the soil when applying static or dynamic loads.This study systematically evaluated stress and energy dissipation mechanisms using laboratory simulations:a plate sinkage test and an adapted Proctor test.The results demonstrated that the straw content(0-20 Mg/hm^(2))dominantly governs dissipation efficiency,with maximum stress dissipation ratios of 45.6%(static load>200 kPa)and energy dissipation ratios of 38.64%(dynamic high-energy).Longer straw(0.20 m)and ordered laying modes enhanced stress dispersion only under low static loads,while dynamic loads exhibited weaker dissipation.The study reveals that the damping effect of straw is strongest under low stress static load,so it is necessary to reduce the compaction of agricultural machinery and optimize the allocation of straw,such as 15-20 Mg/hm^(2),to alleviate compaction in clay loam soils.These findings can provide actionable insights for designing straw-based soil conservation strategies and improving compaction prediction models in mechanized agriculture.展开更多
文摘It had been suggested to use the West African Compaction Test Procedure since the early 1950’s so as to determine the CBR of gravel lateritic soils in West African countries [1]. This test procedure called West African Compaction (WAC) [2] is largely used in road construction in West African countries and had the particularity to be long and use a large amount of material. This note is the result of several comparisons between test procedures taken to determine the CBR from the WAC method to the standardized laboratory test commonly used to determine the CBR.
基金supported by the National Natural Science Foundation of China (Grant Nos.52038005 and 52278342)Natural Science Foundation of Tianjin,China (Grant No.23JCJQJC00160).
文摘The ultrasonic pulse velocity(UPV)correlates significantly with the density and pore size of subgrade filling materials.This research conducts numerous Proctor and UPV tests to examine how moisture and rock content affect compaction quality.The study measures the changes in UPV across dry density and compaction characteristics.The compacted specimens exhibit distinct microstructures and mechanical properties along the dry and wet sides of the compaction curve,primarily influenced by internal water molecules.The maximum dry density exhibits a positive correlation with the rock content,while the optimal moisture content demonstrates an inverse relationship.As the rock content increases,the relative error of UPV measurement rises.The UPV follows a hump-shaped pattern with the initial moisture content.Three intelligent models are established to forecast dry density.The measure of UPV and PSO-BP-NN model quickly assesses compaction quality.
基金supported financially by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA28010402)the National Natural Science Foundation of China(Grant No.32101631)the China Postdoctoral Science Foundation of China(Grant No.2022M721976).
文摘While straw mulching has been recognized for mitigating compaction,the multifactorial effects of straw parameters(content,length,laying modes)under static versus dynamic loads remain poorly quantified.Straw mulching may alter the stress transfer in the soil when applying static or dynamic loads.This study systematically evaluated stress and energy dissipation mechanisms using laboratory simulations:a plate sinkage test and an adapted Proctor test.The results demonstrated that the straw content(0-20 Mg/hm^(2))dominantly governs dissipation efficiency,with maximum stress dissipation ratios of 45.6%(static load>200 kPa)and energy dissipation ratios of 38.64%(dynamic high-energy).Longer straw(0.20 m)and ordered laying modes enhanced stress dispersion only under low static loads,while dynamic loads exhibited weaker dissipation.The study reveals that the damping effect of straw is strongest under low stress static load,so it is necessary to reduce the compaction of agricultural machinery and optimize the allocation of straw,such as 15-20 Mg/hm^(2),to alleviate compaction in clay loam soils.These findings can provide actionable insights for designing straw-based soil conservation strategies and improving compaction prediction models in mechanized agriculture.
