Silty sand can be prone to erosion because it is short of stability cementation materials. In recent years, various emerging soil stabilizers, especially natural organic substance and polymer, have been used to improv...Silty sand can be prone to erosion because it is short of stability cementation materials. In recent years, various emerging soil stabilizers, especially natural organic substance and polymer, have been used to improve soil strength, water stability and ability of erosion resistance. In this study, a new type of soil stabilization additive modified carboxymethyl cellulose(M-CMC), consisting of carboxymethyl cellulose(CMC) and polyacrylamide(PAM), was developed for stabilization treatment of silty sand. A series of laboratory tests were conducted to evaluate the performance of M-CMC application on shear strength, permeability, water susceptibility and microstructure of the silty sand soil treated with additive concentration range of 0%-1.3%. Moreover, rainfall simulation experiments were conducted to evaluate the effect of M-CMC on the erosion control of silty sand which compacted soil in a large-sized runoff(1 m^2) plots. Test plot which treated with 1.1% concentration of soil stabilizer and control plot which treated with same amount of water were cured outdoor for 50 days before rainfall simulation test. Rainfall intensity was applied at 120 mm·h-1 for 60 min. Finally, a field test is performed in order to assess the practical application effect of silty sand with 1.1% M-CMC. In general, the results showed that an increase of the concentration of M-CMC resulted in an improvement in water susceptibility and shear strength but a decrease in the infiltration rate. Internal friction angle of the treated soil remarkably increased under a low M-CMC concentration(less than 0.7%), while cohesion of them sharply increased under a relatively high M-CMC concentration(larger than 0.7%). Water susceptibility of the treated samples was improved remarkably under a relatively high M-CMC concentration(larger than 0.7%). Permeability coefficient of them decreased significantly when the M-CMC concentration was increased from 0 to 0.5% and, then, from 0.9% to 1.3%. Based on the images obtained from a scanning electron microscopy(SEM), the "coating" and "netting" effects were attributable to the observed improvement of the treated soil. When a plot was protected by a thin layer of soil treated with 1.1% MCMC, its erosion resistance was greatly improved, infiltration rate of water and soil loss yield of plot decreased greatly and even though under a rainfall intensity of 120 mm·h-1. The field test with long-term monitoring(three years) confirmed the M-CMC can effectively control erosion of silty sand slopes for a prolonged period of time.展开更多
Development of macro and micro cracks on plastered walls and floors have been studied at different sites under site investigation whereby building inspections, construction history, engineering properties of soil and ...Development of macro and micro cracks on plastered walls and floors have been studied at different sites under site investigation whereby building inspections, construction history, engineering properties of soil and building surroundings assessment were conducted. We did revision of structural calculations and laboratory experiment to find out the source of cracks. Micro and macro cracks have no structural problems on the structure so long as the developed cracks are within the serviceability limit state [1]. There are two main causes of cracks in the structure that are structural and nonstructural sources [2]. The first task was to identify whether the source of cracks are structural or non structural. During site investigation the modes of crack formation, depth and length of crack, crack patterns and direction were studied at different sites in Ngara. Theoretical calculations of crack width and particles size distribution of sand from three main sources were analyzed after performing both sieve analysis and decantation tests. In depth site investigation, literature review and laboratory tests result showed that the causes of cracks are nonstructural and all three reliable sources of sand in Ngara contain more quantities of fines than that specified in BS 882. This paper is looking for the causes of cracks on structures and recommending further research on new idea of using simple technology and low cost methods that is affordable by both the government of Tanzania and local community of Ngara to overcome the problem of structures that develop micro and macro cracks.展开更多
基金financially supported by the National Key R&D Program(2017YFC1501002)the Major Program of the National Science Foundation of China(No.41790445)
文摘Silty sand can be prone to erosion because it is short of stability cementation materials. In recent years, various emerging soil stabilizers, especially natural organic substance and polymer, have been used to improve soil strength, water stability and ability of erosion resistance. In this study, a new type of soil stabilization additive modified carboxymethyl cellulose(M-CMC), consisting of carboxymethyl cellulose(CMC) and polyacrylamide(PAM), was developed for stabilization treatment of silty sand. A series of laboratory tests were conducted to evaluate the performance of M-CMC application on shear strength, permeability, water susceptibility and microstructure of the silty sand soil treated with additive concentration range of 0%-1.3%. Moreover, rainfall simulation experiments were conducted to evaluate the effect of M-CMC on the erosion control of silty sand which compacted soil in a large-sized runoff(1 m^2) plots. Test plot which treated with 1.1% concentration of soil stabilizer and control plot which treated with same amount of water were cured outdoor for 50 days before rainfall simulation test. Rainfall intensity was applied at 120 mm·h-1 for 60 min. Finally, a field test is performed in order to assess the practical application effect of silty sand with 1.1% M-CMC. In general, the results showed that an increase of the concentration of M-CMC resulted in an improvement in water susceptibility and shear strength but a decrease in the infiltration rate. Internal friction angle of the treated soil remarkably increased under a low M-CMC concentration(less than 0.7%), while cohesion of them sharply increased under a relatively high M-CMC concentration(larger than 0.7%). Water susceptibility of the treated samples was improved remarkably under a relatively high M-CMC concentration(larger than 0.7%). Permeability coefficient of them decreased significantly when the M-CMC concentration was increased from 0 to 0.5% and, then, from 0.9% to 1.3%. Based on the images obtained from a scanning electron microscopy(SEM), the "coating" and "netting" effects were attributable to the observed improvement of the treated soil. When a plot was protected by a thin layer of soil treated with 1.1% MCMC, its erosion resistance was greatly improved, infiltration rate of water and soil loss yield of plot decreased greatly and even though under a rainfall intensity of 120 mm·h-1. The field test with long-term monitoring(three years) confirmed the M-CMC can effectively control erosion of silty sand slopes for a prolonged period of time.
文摘Development of macro and micro cracks on plastered walls and floors have been studied at different sites under site investigation whereby building inspections, construction history, engineering properties of soil and building surroundings assessment were conducted. We did revision of structural calculations and laboratory experiment to find out the source of cracks. Micro and macro cracks have no structural problems on the structure so long as the developed cracks are within the serviceability limit state [1]. There are two main causes of cracks in the structure that are structural and nonstructural sources [2]. The first task was to identify whether the source of cracks are structural or non structural. During site investigation the modes of crack formation, depth and length of crack, crack patterns and direction were studied at different sites in Ngara. Theoretical calculations of crack width and particles size distribution of sand from three main sources were analyzed after performing both sieve analysis and decantation tests. In depth site investigation, literature review and laboratory tests result showed that the causes of cracks are nonstructural and all three reliable sources of sand in Ngara contain more quantities of fines than that specified in BS 882. This paper is looking for the causes of cracks on structures and recommending further research on new idea of using simple technology and low cost methods that is affordable by both the government of Tanzania and local community of Ngara to overcome the problem of structures that develop micro and macro cracks.
