Experimental Study On The Effect Of Temperature Rise On The Adhesion Between Soil And Metal Interface

When the EPB crosses in the area of rich viscosity and high moisture content,the cut slag will gradually form mud cake on the surface of the cutterhead,and for the accumulation of mud cake,it will block the cutterhead opening,and cause problems such as increased cutterhead torque and tool wear.At the same time,due to the extrusion of the cutterhead and the friction of the partition in the soil compartment,the temperature of the mud cake on the surface of the cutterhead rises rapidly,which may aggravate the production of mud cake.However,some studies also show that temperature can reduce the viscosity between the interfaces.Therefore,this paper mainly carries out the interface adhesion test from the tangential and normal directions,analyzes the influence of different factors on the interface adhesion,and focuses on the influence of temperature on the interface adhesion,the main research content and conclusions are as follows:(1)In the experimental study of normal interface adhesion,the normal adhesion force between metal plate and soil is measured by loading and pulling the soil sample with a pull-out instrument with uniform motion.The normal drawing force under different preloads,different loading rates,different drawing rates,different moisture content and different loading time were studied.At the same time,the comparative experiment of heating was carried out to explore the effect of temperature on the normal adhesion force.The test shows that the normal adhesion force will increase with the increase of preload,and the change of preload is one of the main factors causing the change of normal adhesion force.The effect of loading rate and drawing rate on the normal adhesion force is different.The change of loading rate has little effect on the normal adhesion force,and the normal adhesion force will increase with the increase of drawing rate.By changing the moisture content of soil samples in the experiment,it is found that the normal adhesion will increase with the increase of moisture content,and the increase rate of normal adhesion is faster at lower moisture content(30% ～ 35%);When the moisture content is high(35% ～ 40%),the normal adhesion is close,and the moisture content has a great influence on the adhesion of unsaturated soil.(2)On the basis of loading,the metal plate surface is heated at the same time.Comparing the normal adhesion force under heating and no heating conditions,it is found that heating has a great influence on the normal adhesion force.With the increase of heating time,the phenomenon of viscosity reduction will appear.When the heating time is short,the effect of reducing viscosity can not be played.With the heating time,the effect of reducing viscosity continues to increase,but with the further increase of heating time,the normal adhesion will gradually increase and the effect of reducing viscosity will gradually decrease.At the same time,observing the interface adhesion,it is found that a large amount of water film remains at the interface without heating,which decreases sharply after heating.With the increase of heating time,the residual water film decreases more.It can be found that the normal adhesion mainly depends on the interface water film,and the temperature also has a great influence on the thickness of water film.(3)In the study of tangential adhesion test,the shear box in the direct shear instrument is mainly improved,and the metal plate is installed on the lower shear box as the shear surface,so as to measure the interfacial shear force.By changing the soil moisture content in the test,it is found that the interfacial shear strength decreases gradually with the increase of soil moisture content,and even tends to zero.When the moisture content is lower than the plastic limit,the interfacial shear force is much greater than the soil sample with the moisture content between the liquid plastic limit.Under the condition of no heating,when the shear value tends to be stable,turn on the power supply to heat the metal interface.By changing the heating time,it is found that heating has a significant effect on reducing the viscosity of the interface.With the increase of heating time,especially when the heating time reaches 30 s,the shear strength decreases obviously.However,with the increase of moisture content,under higher vertical load,with the further increase of heating time,the shear strength increases.By changing the power supply voltage,so as to change the heating rate,it is found that with the increase of voltage,the viscosity reduction effect caused by heating is also enhanced,and the greater the vertical load is,the smaller the influence of the change of heating rate on the tangential adhesion force is.