Study On Mechanical Properties Of MICP Solidified Vegetation Root-soil Composites

Vegetation slope protection has the advantages of green environmental protection,inexpensive and convenient construction.It is a common treatment scheme for slope ecological restoration at present.However,in practical engineering,there are some problems in vegetation slope protection,such as slow root growth in the early stage,loose root-soil combination and limited slope protection depth,resulting in insufficient vegetation slope protection capacity.At present,based on the interdisciplinary integration,it has significant advantages in dealing with traditional geotechnical problems.Microbial induced calcium carbonate precipitation(MICP)is a new biological reinforcement technology,which can solidify soil and promote vegetation growth.Therefore,microbial mineralization is proposed to cooperate with vegetation slope protection.The mechanical parameters and strength of microbial solidified vegetation root-soil composites are the core issues of this technology.In this paper,taking the roots of three herbaceous plants as the research object,microorganisms are used to strengthen the vegetation root-soil composites.On the basis of considering the variables such as root content and root diameter,a series of root-soil composite plus solid unconfined compression tests and triaxial tests are carried out.To explore the change law of root content on root-soil composite plus solid mechanics,analyze the curing effect of microorganisms,establish the curing mathematical model,and reveal the strength change mechanism of microbial mineralization strengthening root-soil composite.The main results and conclusions of this paper are as follows:1.In this paper,the selection and cultivation of the selected microbial immobilized strains are firstly studied,including experimental studies on microbial activation,microbial expansion culture,microbial preservation,etc.,and the changes in microbial enzyme activity during the cultivation process are analyzed.culture conditions.At the same time,the mechanical properties of different vegetation root systems(Bermuda grass,Festuca arundinaria,and Dwarf lilyturf)were also studied.The tensile test of the vegetation root system and the unconfined compression test of the root-soil composites were mainly used.The results showed that the resistance of the three root systems was The tensile force was positively correlated with the diameter,and the tensile strength was negatively correlated with the diameter.Comparing the tensile strength curves of the three root systems,it was found that the tensile strength of the root system of Bermuda grass was relatively large.The unconfined compressive strength of the root-soil composites of the three root systems is between 60 and 95 k Pa.Compared with the strength of the plain soil,the maximum increase in the shear strength of the Bermuda grass root system to the soil is 72.67 k Pa.In the follow-up microbial solidification root-soil composites test.2.The root system of Bermuda grass was selected as the research object,and a triaxial test of the change of root content and microbial solidification on the strength of the root-soil composites was carried out,and the reinforcement was carried out by the syringe grouting method.The strength of the composite increases first and then decreases.When the optimal root content is 1.0%,the cohesion of the root-soil composite is 45.20 k Pa and the internal friction angle is 17.57°,which is 10.1 higher than that of the plain soil.k Pa,while the internal friction angle only increases by 3.35°.When the Bermuda grass root-soil composites was cured by microorganisms,the effect on the cohesion was obvious.The "contribution degree" was introduced to analyze the microbial reinforcement effect.The results showed that the microbial solidification could increase the strength of the root-soil composites by 62.79%-139.01%,which was a significant improvement.The calcium carbonate formed by microbial reinforcement is adsorbed on the surface of the root system,increasing its roughness and improving the strength of the root-soil composites.3.PLAXIS 3D numerical simulation software is used to analyze the displacement and stability of slope soil mass by combining microbial solidification cooperative vegetation slope protection with practical engineering.The results show that the displacement of slope with vegetation slope protection is 29.94 mm and the strain value is 1.517%,while the displacement of slope with MICP solidification cooperative vegetation slope protection is 12.40 mm and the strain value is 5.981×10-3%.Compared with vegetation slope protection alone,microbial cooperative vegetation slope protection can reduce the slope displacement by 17.54 mm and the strain by two orders of magnitude.The research results of this project can provide an experimental basis for the engineering application of microbial reinforcement and vegetation slope protection in the joint treatment and restoration of slope ecology,and also help to realize the coordinated development of engineering construction and ecological protection.