| Rare earth is an important strategic mineral resources.Ion-type rare earth deposits in Ganzhou are rich in reserves.Long-term mining of ion-type rare earth deposits has led to the destruction of the ecological environment around the in-situ leaching field.Landslides,collapses,debris flows and other geological disasters occur frequently.The slope protection technology of herbaceous plants and ecological soil stabilizer has been widely used in slope protection projects of common soil slopes such as highway slopes and river slopes.In view of the soil characteristics and climatic conditions of the in-situ leaching site of ionic rare earth mines,the slope protection technologies of herbaceous plants and ecological soil stabilizers were studied in depth to provide more effective engineering methods for ecological slope protection of in-situ leaching site of ionic rare earth mines.In this paper,the slope of an ion-type rare earth ore in-situ leaching site in Lingbei Town,Dingnan County is taken as the research object.The field investigation is carried out on the current situation of the local in-situ leaching site.The soil samples of the slope are collected in the in-situ leaching site,and the physical and mechanical properties of the slope soil are tested by experiments.The collected in-situ leaching slope soil was used to plant 12 kinds of grasses such as ryegrass,green grass,and Bermudagrass for comparative test.The 15 index data were compared and the herbaceous plants with the best environmental adaptability were screened by analytic hierarchy process(AHP)to analyze and study the soil fixation effect of herbaceous plant roots.According to the characteristics of root soil fixation,the soil fixation effect of polyurethane curing agent was studied.The two kinds of slope protection technology were combined.The effect of comprehensive slope protection technology combined with herbaceous plants and ecological curing agent was verified by indoor simulation of slope erosion test.The results showed that the comprehensive slope protection technology improved the soil erosion of slope and played a good slope protection effect.The main conclusions are as follows :(1)Physical and mechanical parameters such as average bulk density,average natural moisture content,liquid-plastic limit,particle size distribution,and shear strength under different moisture contents were obtained through laboratory tests.The results show that due to the long-term erosion of the leaching agent,the local sandy clay has poor structure and poor gradation.When the soil moisture content was between10% and 25%,the cohesion and internal friction angle showed a linear downward trend,and the change was small.After the moisture content increased from 25%,it was close to the plastic limit moisture content,and the cohesion and internal friction angle were greatly reduced,so the soil water sensitivity was strong.(2)15 indexes of 12 kinds of herbaceous plants were observed,and the multi-index evaluation model was established by analytic hierarchy process.Finally,through the weight ranking,it can be seen that the comprehensive evaluation of Lolium Perenne,Green Bristlegrass and Cynodon Dactylon is the best,and the weight is more than 0.1.It is suitable to be used as herbaceous plants for slope protection of ionic rare earth mines in southern Jiangxi.The poor comprehensive evaluation is Trifolium Repens and Trifolium Pratense,and the weight is less than 0.05.It is not suitable to be used as herbaceous plants on the slope of ion-type rare earth mines in Ganzhou.(3)The cohesion of root-soil composite increases,and the internal friction angle changes little.With the increase of water content,the increase of shear strength of rootsoil composite decreases gradually;when the root content reached 6%-8%,the cohesion of root-soil composite gradually no longer increased.The curve of water content of 15%and the curve reached the peak value of cohesion when the root content reached 8 %.When the root content was more than 8%,the cohesion of root-soil composite had a downward trend.With the increase of root content,the permeability coefficient of rootsoil composite decreased and the permeability resistance increased.(4)The polyurethane curing agent with the concentration less than 20% after dilution is a kind of soil curing agent with good ecological property.Spraying in the soil will form a curing layer,and the curing thickness will increase with the increase of curing time and dilution concentration.When the curing time reaches 720 min,the thickness of the curing layer will not increase.The soil solidified by curing agent showed good performance in the disintegration test.With the increase of concentration and curing time,the stability time in water increased,and the disintegration speed slowed down.With the increase of curing agent concentration,the cohesion c and internal friction angle φ of the solidified soil are greatly improved,but the cohesion c is greatly increased with the increase of curing time.When the curing time reaches 12 h,the cohesion c does not increase,and the internal friction angle φ changes slightly with the curing time.(5)With the increase of rainfall,the soil loss of soil slope increases.The comprehensive slope protection combined with curing agent slope protection and herbaceous plant slope protection has the best effect on resisting rainwater erosion,followed by curing agent slope protection and herbaceous plant slope protection.It was verified that the comprehensive slope protection technology combining herbaceous plant slope protection and ecological soil stabilizer had the best slope protection effect combining the advantages of the two slope protection technologies.The comprehensive slope protection enhanced the ability of soil to resist rainwater erosion,slowed down the speed of soil erosion,enhanced the effect of herbaceous plant slope protection,greatly improved the living environment of vegetation,and had good popularization and application value. |
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