Experimental Study On The Mechanism Of Interaction Between Sensor-enabled Geogrids And Soils

With the development of public infrastructure such as roads and railways in China,many engineering disasters have occurred,such as collapse of highway subgrade and railway subgrade,cracking of highway pavement,slope sliding,etc.In order to prevent these engineering disasters,geogrids are widely used in various fields,including soft soil foundation reinforcement,underground tunnel reinforcement and so on.These geogrids greatly improve the mechanical properties of composite structures by the interaction between grids and soil,so that they can protect these structures during their service life.At present,the interaction between reinforcement and soil is based on the traditional geogrid,but there are no researches on the sensor-enabled geogrids(SEGG).In addition,the previous researches are mostly conducted under the limit equilibrium condition.The lacking of researches on the evolution of the interaction may lead to the failure of the grid reinforced structure under the non-limit condition.In order to further study the evolution of the interaction and improve their practical application,the SEGG made of high density polyethylene(HOPE)and carbon black(CB)materials are used in this paper,and different geometric sizes of smart geogrids are designed by laser cutting technology.Laboratory tests and theoretical analysis are carried out.The pull-out performance of SEGG with different geometric sizes in different soils was studied.Uniaxial tension test and direct shear test were also carried out.The interaction between SEGG and soil was analyzed.The following conclusions were drawn:(1)The results of uniaxial tensile tests show that the stress-strain curve of SEGG is approximately hyperbolic,while the results of uniaxial slow tensile tests show that the normalized resistance-strain curve is a parabolic shape.(2)The results of direct shear test show that the greater vertical pressure leads to larger shear strength in both sandy soil and gravels;the shear stress is not a constant,but varies with the displacement of SEGG.(3)The results of pullout tests show that the maximum pullout force increases with the number of transverse ribs,while the difference between the maximum pullout force of SEGG with two transverse ribs and three transverse ribs is less,as larger vertical pressure leads to the short effective reinforcement length of geosynthetics in soil.(4)The results of pullout tests show that the greater vertical load results in the larger pullout force.In addition,compared with the SEGG specimens with transverse ribs,the interaction between the SEGG specimens without transverse ribs and soils is more affected by the vertical load.(5)The results of pullout tests show that the pull-out behavior of SEGG is related to the soil(i.e.sandy soil and gravel)used in the test.When the vertical load is 20kPa,the maximum pullout force of SEGG in gravel is obviously larger than that of SEGG in sand,while the difference between the maximum pullout force of SEGG in gravel and sand is smaller under 30kPa vertical pressure.However,when the vertical load is 50kPa,the maximum pullout force of SEGG with three transverse ribs in gravel is larger than that in sand,while the maximum pullout force of SEGG with other geometric size in sand is higher than that in gravel.(6)It can be observed from the results of pullout tests that the transverse ribs are responsible for a significant fraction of the ultimate pullout load,while friction along SEGG length is small.With the increase of vertical load,the fraction of the maximum pullout force due to skin friction slightly increases,while that due to bearing resistance slightly decreases.However,the difference between the frictional resistance of the longitudinal rib and the transverse rib of SEGG with two transverse ribs decreases,as the area of the transverse rib increases.(7)Compared with the results of pullout test in sand,under normal pressure of 20 kPa and 30 kPa,the bearing resistance of transverse ribs accounts for a larger proportion of pullout force in gravel,while the bearing resistance of transverse ribs holds a smaller proportion of pullout force in gravel under normal pressure of 50 kPa.