| As a treasure of the Chinese nation,the earth ruins contain many historical,scientific,cultural,and social values,leaving many valuable information for future generations.The widely distributed soil sites in China are the most difficult to protect in the protection of cultural relics.Due to its long history,the basic physical properties of the soil itself are poor,the environmental impact is serious,and the awareness of human cultural relics protection is weak.Many cultural relics have been affected to varying degrees.The damage is urgently needed for reinforcement protection.The protection of cultural relics in the Kaifeng semi-arid area has not yet formed a mature theoretical system,and the research methods and techniques for the protection of cultural relics are not mature enough.Therefore,it has great value and significance for the study of site protection in Kaifeng area.At present,the reinforcement materials for soil sites are mainly divided into three categories,namely organic materials,inorganic materials and organic-inorganic composite materials.As a kind of organic material,silicone water repellent SHP-60 is widely used in building wall,gypsum,mortar and other surface protection agents,showing good water resistance,but has not seen relevant research in the application of site soil.In this paper,taking the foundation soil of Kaifeng old city wall as an example,taking the compressive strength of the site soil as a reference,using lime to imitate the site soil,the improvement effect of the silicone water repellent SHP-60 on the imitation site soil was explored.Through pre-test trial matching,this paper identifies four types of 16 samples of imitation site soil,containing 0%,1%,3%,5% by mass of silicone water repellent.Through the capillary water absorption,water immersion disintegration,mechanical properties,freeze-thaw cycle and acid and alkali resistance test,the effect of SHP-60 modified imitation site soil was explored,and the internal morphology changes were analyzed by scanning electron microscopy to reveal the effect of SHP-60 strengthening imitation land.mechanism.The main research contents are as follows:(1)The capillary water absorption test in laboratory showed that SHP-60 could change the capillary water absorption law of soil obviously.The 24-hour capillary water absorption quality of soil sample decreased gradually with the increase of SHP-60 content.1% organ silicon hydrophobic agent content improves the effect poorly,the water absorption quality is still high and the capillary water rises greatly;5% organ silicon hydrophobic agent content reduces the water absorption quality of imitation site soil by about 90% compared with that before improvement,the appearance of soil sample is complete,effectively changing the capillary effect of soil sample,thus improving the water resistance of soil.(2)Through the immersion disintegration test of imitated site soil,it is found that SHP-60 can resist the erosion of immersed water very well.The water-immersion and disintegration resistance of the improved soil samples were improved obviously,and the number of bubbles and the degree of reaction intensity decreased with the increase of SHP-60 content.Soil samples with 1% organ silicon hydrophobic agent content still disintegrate or produce a large number of bubbles;soil samples with 5% organ silicon hydrophobic agent content have the best water stability,almost no bubbles in the water,and are still dry within 7 days of immersion,basically achieving the function of water isolation.At the same time,it is conjectured that there are differences in waterproofing performance of soil samples with different densities.(3)Through mechanical properties test,it is found that SHP-60 can improve the compressive strength,cohesion and friction angle of soil.The unconfined compressive strength of soil sample is proportional to the content of SHP-60 and curing age.The unconfined compressive strength of soil sample can be increased by 2.94 times in 28 days,the cohesion of soil sample can be increased by 97.47%,and the friction angle can be increased by 48.9%.(4)In order to explore the durability of imitated improved soil,freeze-thaw cycling test and acid-alkali erosion resistance test were carried out to obtain the compressive strength of soil samples after erosion.The compressive strength and mass loss rate of the soil samples after freezing and thawing cycles were lower than those of the soil without SHP-60 water-repellent powder,showing good resistance to the freezing and thawing cycles.After 5 cycles of acid-based solution erosion,the soil sample remained intact and the strength decreased by only 14.25%,still maintaining a high strength.(5)After the improvement of SHP-60,the microstructure of soil samples changed,the internal pores decreased,and the surface of SHP-60 adsorbed soil agglomerated and connected to form a waterproof membrane,which increased the water resistance and mechanical properties of the soil samples.The stability of the soil sample has been greatly improved.The silicone water repellent SHP-60 can change the microstructure of the imitation site soil,reduce the internal pores,increase the compactness of the soil sample,and form a waterproof membrane to improve the hydrophobic properties of the surface tension,thereby effectively improving the water resistance and mechanics of the imitation site soil.And durability.3%~5% of silicone hydrophobic agent can effectively block the erosion of underground capillary water and water immersion,improve mechanical properties and durability.The research results provide a new idea for the restoration of soil sites in Kaifeng. |
