Research And Development Of TBM Bean Gravel Backfill Grouting Material And Its Hydration Mechanism

In order to overcome the problem of insufficient material properties facing the improvement of bean gravel backfill grouting quality,ensure the high efficiency of TBM project construction,save capital investment and protect the ecological environment,this paper starts from the basic theory of cement material compound,takes ordinary Portland cement,high belite sulfoaluminate cement and gypsum dihydrate as raw materials,and adopts the method of "uniform design" to design the test scheme.A new type of high performance cement-based backfill grouting material was developed through a series of physical and mechanical properties tests,and its hydration mechanism was revealed by means of EIS,XRD and SEM.The main research achievements are as follows:(1)Developed a series of high performance cement-based grouting materials to meet the requirements of TBM backfill grouting engineering,among which P5 ratio has the best comprehensive performance(ordinary Portland cement: High Belite sulfoaluminate cement:gypsum dihydrate = 76.88%22.59% : 0.53%),the water extraction rate,stone rate and fluidity of the grouting material with this proportion are 1.6%,98.28%,335 mm,and the bending strength and compressive strength of 5.23 MPa and 17.36 MPa after curing for 28 d,which can meet the requirements of grouting engineering and have the value of application and popularization.(2)The long-term soaking system was used to study the deterioration law of grouting materials under sulfate solution attack from four aspects: morphology,mass change,mechanical properties and corrosion resistance coefficient.The results showed that the quality of grouting materials under different concentrations of soaking increased with the extension of erosion age,and the increase rate was higher than that of clear water group.The flexural strength,flexural corrosion resistance coefficient,compressive strength and compressive corrosion resistance coefficient of the specimens firstly increased and then decreased with the immersion age increasing.The flexural strength and compressive strength of specimens increased first and then decreased with the concentration of sulfate solution.The compressive strength and compressive strength of specimens reached the maximum when the immersion concentration of sulfate solution was 55g/L.(3)The freeze-thaw resistance characteristics of grout materials were studied from two aspects: elastic modulus and compressive strength.The results showed that the compressive strength and elastic modulus of grout materials decreased with the increase of the number of freeze-thaw cycles,and the change rate was slow in the early stage of the test,but accelerated in the late stage of the test.(4)The hydration process,hydration products and microstructure of grout materials were characterized by EIS,XRD and SEM,and the hydration mechanism was revealed.The results are as follows: There was no electrochemical reaction in the early stage of hydration,and the high frequency band was an oblique line.The high frequency band was a curve in the middle stage,and the Nyquist curve was complete in the late stage.The types of hydration products of grouting materials are similar to those of ordinary Portland cement,mainly CH,C-S-H and AFt,etc.The relative content and formation time of each product vary with the hydration environment.The needle-rod calcium-vanadite is interleaved and bonded to form a skeleton,in which CH and C-S-H gel phases fill,forming a relatively dense structure.