| Puyang is one of the birthplaces of human civilization,located in the middle and lower reaches of the Yellow River,known as the "dragon town of China";Qicheng site is located in the urban area of Puyang City,a famous city in the Spring and Autumn Period in history,which is deeply affected by the flood of the Yellow River in history.So it is of great significance to study and protect it;The soil in this area is mostly silty soil formed by the flood and impact of the Yellow River.The water stability is poor,and the capillary water plays a large role,the strength is high when it is dry,but decreases significantly when it is wet.After thousands of years of wind and sun and the influence of human activities,Qicheng site has become scarred It is urgent to improve the mechanical properties of the earthen site,taking Qicheng site as an example,a systematic scheme of protection and reinforcement of the earthen site is established,which has a good reference for the protection of the earthen site in the Yellow River BasinThis paper takes Qicheng site soil of Puyang as the research object to prepare imitated site soil,through a series of experimental studies,MICP technology and improved MICP technology are used to strengthen the mechanical properties of imitated site soil,the test contents and results are as follows(1)Based on XRF analysis,the content of oxides in site soil and site soil is obtained,seven oxides with a content of more than 1%are selected for data analysis and research,and a seven element first-order equation set is established and solved.The imitated site soil was prepared by adding 8.52g SiO2,0.45g Al2O3 and 0.15g CaF2 per 100g of site soil;Through a series of geotechnical tests,it is found that the proportion of soil particles,coefficient of non-uniformity,coefficient of curvature,liquid limit,plastic limit,optimum moisture content and maximum dry density of the imitated site soil and the site soil are slightly different,but the difference is not significant,mainly due to the addition of three substances with smaller particle size;Under the premise that the soil sampling location is near the earthen site and the basic physical properties of the two soil particles are similar,the prepared site like soil is used for subsequent mechanical test research,which points out a new direction for the protection and restoration of the earthen site(2)In this paper,the glutinous rice slurry was introduced into the MICP technology as an improved material to study the mechanical properties of 0%,1%,3%,5%,7%,9%glutinous rice slurry and 7-day-old imitated site soil samples,with the increase of the glutinous rice slurry concentration,the cohesion of the samples increased linearly,the internal friction angle and the unconfined compressive strength increased first and then decreased,among them,the unconfined compressive strength and internal friction angle of the sample reached the maximum at 3%glutinous rice pulp concentration;According to the theoretical formula,the characteristic value of bearing capacity of soil foundation with 3%glutinous rice slurry concentration is the largest,which verifies the reliability of unconfined compressive strength test The improved MICP technology was improved by introducing the concentration of 3%glutinous rice slurry as the improved material into the medium,and the activity of the improved microorganism was higher than that of the ordinary microorganism(3)The core of MICP technology is to induce Ca2+ in cementitious liquid to form CaCO3 precipitate,and to study the production of CaCO3 precipitate under different concentration of cementitious liquid,the same mass ratio(2:1),the same concentration of cementitious liquid(0.5m)and different mass ratio of cementitious bacteria,It is concluded that when the concentration of cementation fluid is 0.5m and the ratio of cementation fluid and bacteria is 2:1,the production of CaCO3 is the most,and the conversion rate of Ca2+ is more than 80%;Using 3%glutinous rice slurry as the modified MICP technology,we found that the conversion of Ca2+ was more than 90%,which was 10%higher than that of MICP technology.The microstructure of the reaction product of MICP technology and modified MICP technology was observed by SEM scanning.Because of the addition of glutinous rice slurry in the modified MICP technology,we found that there was a layer of film on the surface of the reaction product,which appeared to be structure more dense(4)Through the direct shear test and unconfined compressive strength test,the mechanical properties of the three samples were determined,The main mechanical indexes were cohesion,internal friction angle and unconfined compressive strength.Under the same maintenance days,the mechanical index of modified MICP imitated site soil sample was the highest,followed by MICP imitated site soil sample,and the imitated site soil sample was the lowest;The mechanical index of modified MICP imitated site soil samples increased significantly from 7 to 14 days;The cohesion of MICP imitated site soil samples increased significantly from 7 to 14 days,and the other mechanical indexes increased slowly;The mechanical indexes of the imitated site soil samples increased little from 7 to 14 days;and the mechanical indexes of the three samples increased slowly from 14 to 28 days.After curing for 28 days,the mechanical indexes of the three samples reached the maximum,the cohesion,internal friction angle and unconfined compressive strength increased about 77%,27%and 120%respectively;The research shows that the MICP technology can improve the cohesion of soil,but the strengthening effect of the internal friction angle is not obvious;the improved MICP technology can not only improve the cohesion of soil,but also improve the internal friction angle,so that the mechanical properties of soil can be strengthened(5)The samples of site soil,soil,imitated site soil,MICP imitated site soil and improved MICP imitated site soil were analyzed by color difference analyzer,The color difference between site soil and soil,imitated site soil,MICP imitated site soil is less than 1,which indicates that the three groups of samples can replace site soil in visual research,The color difference between the site soil and the modified MICP imitated site soil is greater than 1,so the protection and restoration of the site soil can be carried out by combining the modified MICP imitated site soil with the MICP imitated site soil. |
