| The area of our precious soil sites which include more than ten places in the world heritage list is huge.Those sites are the main carrier of the history of the development of civilization in China,with a non-renewable and irreplaceable value and status.However,with the passage of time,most of soil sites have been subjected to serious diseases and some sites are precarious,showing defective serious or the tendency to go to the devil.Therefore,these national treasures are in need of emergency rescue.From the present research situation,there is still not a reliable reinforcement material to prevent soil sites from weathering,especially in more humid environment.So it is valuable to systematically and penetratingly study the reinforcement of soil sites in humid environment.Meanwhile this research will be widely applied in the protection projects.The ideal preservation materials of soil sites meet the following requirements:the composition is close to the soil;they can resist the destruction of natural environment;the protective layer formed by reinforcement materials should have the texture of the soil and keep the air permeability and water permeability of original soil.Based on these requirements,reinforcement materials which can prevent weathering and are suitable for soil sites in damp environment have been designed.The influence of solvent,the type of alkali catalyst,precipitation agents and cross-linking agents on the cross-linking structure of soil aggregate has been explored and the role of alkali on soil minerals has been preliminary studied in this thesis.1.Absolute ethanol with smaller dielectric constant was chosen as the dispersant,barium hydroxide and oxalic acid or barium hydroxide and oxalic acid mixed with phosphoric acid as reinforcing agents.Remolded soil samples were reinforced for two cycles in situ,and then they were placed for some time.Color change,weight change,pH change,permeability and pore size change were tested to evaluate consolidation effect.At the same time,under different extreme conditions such as dry heat aging,salt erosion,soaking and freeze-thaw,the samples were treated to evaluate the consolidation effect.Test results show that the optimal concentration of reinforcement materials is 10 g/L Ba(OH)2 solution and 2.0%C2H2O4 solution.The alkaline environment and the color of soil don't change after reinforced.The weight increases to varying degrees,but the increased ratio is less than 5%,which is in line with the requirements of the protection of cultural relics.The air permeability has increased and the increasing in the ratio of macro pore can explain why the air permeability of soil changes.The soil samples are more resist to aging after treated,especially when reinforcing agents contain phosphoric acid.Thus it can be seen that whether oxalic acid contains phosphoric acid exerts a tremendous influence.The content of smectite in soil samples decreases after treated,while the content of SiO2 increases.2.Absolute ethanol was chosen as the dispersant,respectively ? tetraethoxysilane(TEOS);? Ba(OH)2 and TEOS;? Ba(OH)2,TEOS and C2H204 as reinforcement materials.Remolded soil samples were reinforced for two cycles in situ,and then they were placed for some time.Finally various performance tests were carried out to evaluate the consolidation effect synthetically.Test results show that the optimal concentration of reinforcement materials is 10 g/L Ba(OH)2 solution,2.0%C2H2O4 solution and 25%TEOS solution.Three samples show good consolidation effect.The alkaline environment and the color of soil don't change after reinforced.The weight increases to varying degrees,but the increased ratio is less than 5%,which is in line with the requirements of the protection of cultural relics.The air permeability has increased and the third sample has the best air permeability.They are all resist to aging after treated and in the test period,performance is not very different.Three kinds of reinforcement agents are low-cost,easy operation,environment-friendly and suitable for the protection of soil sites in humid environment.3.Absolute ethanol was chosen as the dispersant,respectively ?tetramethoxysilane(TMOS);? Ba(OH)2 and TMOS;? Ba(OH)2,TMOS and C2H2O4 as reinforcement materials.Remolded soil samples were reinforced for two cycles in situ,and then they were placed for some time.Finally various performance tests were carried out to evaluate the consolidation effect synthetically.Test results show that the optimal concentration of reinforcement materials is 10 g/L Ba(OH)2 solution,2.0%C2H2O4 solution and 25%TMOS solution.The alkaline environment and the color of soil don't change after reinforced.The weight increases to varying degrees,but the increased ratio is less than 5%,which is in line with the requirements of the protection of cultural relics.The air permeability has increased and the third sample has the best air permeability,followed by the second sample and the first sample.The mean pore size increases but the proportion of micro pore changes little.The increasing in the ratio of macro pore can explain why the air permeability of soil changes.They are all resist to aging after treated and in the test period,performance is not very different.Three kinds of reinforcement agents are low-cost,easy operation,environment-friendly and suitable for the protection of soil sites in humid environment.However,the price of TMOS is much higher than that of TEOS,so it is reasonable to choose TEOS as cross-linking agent from the economic point of view.4.Absolute ethanol was chosen as the dispersant,respectively ? NaOH and TEOS;? KOH and TEOS;? Ba(OH)2 and TEOS as reinforcement materials.Remolded soil samples were reinforced for two cycles in situ,and then they were placed for some time.Finally various performance tests were carried out to evaluate the consolidation effect synthetically.Test results show that the optimal concentration of reinforcement materials is 0.05 mol/L NaOH solution,0.05 mol/L KOH solution,10 g/L Ba(OH)2 solution and 25%TEOS solution.The alkaline environment and the color of soil don't change after reinforced.The weight increases to varying degrees,but the increased ratio is less than 5%,which is in line with the requirements of the protection of cultural relics.The air permeability has increased and the third sample has the best air permeability,followed by the second sample and the first sample.They are all resist to aging after treated.As a kind of base reinforcement agent,Ba(OH)2 has another protective result because it can't bring soluble salts to the soil.In the test period,performance is not very different.5.Two commonly used inorganic alkali such as NaOH,KOH and Ca(OH)2 aqueous solution reacted with soil samples A for two month at 60 ? under the nitrogen atmosphere.Then the soil samples before and after treated were tested by XRD,XPS,TEM and SEM.Test results show that after the alkali treatment,the electron binding energy of silicon atom becomes smaller which suggests that the condensation reaction occurs in the soil minerals under the alkaline condition,Si-OH decreasing and Si-O-Si increasing.And the surface topography of soil samples has undergone great change.The role of Ca(OH)2 is the weakest and it only has effect on smectite,while NaOH and KOH can also destroy other minerals and generate various inorganic minerals.Soil samples treated with NaOH generate blique calcium zeolite.Soil samples treated with KOH generate chabazite,multi-crystalline illite-smectite mixed-layer structure and amorphous silicon-rich mineral.6.Sample B was obtained through getting rid of organic matter and carbonate from sample A.Three commonly used inorganic alkali such as NaOH,KOH and Ca(OH)2 aqueous solution reacted with soil sample B for two month at 60 ? under the nitrogen atmosphere.Then the soil samples before and after treated were tested by XRD,XPS,TEM and SEM.Test results show that after the alkali treatment,the electron binding energy of silicon atom becomes smaller.And the surface topography of soil samples has undergone great change.The role of Ca(OH)2 is the weakest and it only has effect on smectite,while NaOH and KOH can also destroy other minerals and generate various inorganic minerals.Soil samples treated with NaOH generate blique calcium zeolite.Soil samples treated with KOH generate chabazite,multi-crystalline illite-smectite mixed-layer structure and amorphous silicon-rich mineral.The results of alkali treatment of sample A and sample B suggest that whether soil samples contain organic matter and carbonate has little effect on the condensation reaction.Test results show that after the alkali treatment,the electron binding energy of silicon atom becomes smaller.And the surface topography of soil samples has undergone great change.The role of Ca(OH)2 is the weakest and it only has effect on smectite,while NaOH and KOH can also destroy other minerals and generate various inorganic minerals.Soil samples treated with NaOH generate natrolite.Soil samples treated with KOH generate chabazite,and multi-crystalline illite-smectite mixed-layer structure.The composition of soil sample A and B is slightly different.The new generation minerals belong to zeolite minerals which are hard and can prevent weathering.The different roles of alkali on soil inorganic minerals can provide a new thinking or method,which can guide the protection of soil sites in situ and make the protection have more scientific predictability. |
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