| Geotextile is a kind of industrial textile which is made from fiber or fiber-forming polymer by means of needle punching,spunbonding and weaving.Because of its high strength,aging resistance,good filtering,protection,drainage and other properties,it has been widely used in various civil engineering,such as landfill,mines,tunnels and other fields.Geotextile is one of the most important parts of anti-seepage system in landfill.Its function is to isolate the geomembrane from the garbage soil to prevent the geomembrane from being punctured or dissevered by sharp objects in the garbage soil.However,the decomposition of organic matter in garbage soil,natural rainfall,earthquake and other reasons may lead to the garbage soil on the side slope of landfill tend to fall or settlement,lead to the geotextile to be fractured due to huge tension,causing local or even overall instability of the landfill,toxic and harmful waste liquid leakage,resulting in serious environmental pollution.Therefore,it is of great scientific significance and practical value to prepare the a kind of polytetrafluoroethylene(PTFE)self-lubricating composite geotextile to reduce the tension in geotextile on the landfill side slope and improve its anti-break reliability.In this paper,the force role and interface shear mechanism of geotextile on landfill side slope was analyzed firstly.Then,the PTFE micropowder was modified by trimethyl borate and the modification mechanism and technology were studied,to improve the lubricating property of PTFE solid lubricating layer.Finally,a self-lubricating PTFE composite geotextile was prepared and the surface/cross section morphology,mechanical properties,interface shear mechanism,durability and anti-break reliability were analyzed.The research work and results have been summarized in the following respects:(1)The force role and equation of geotextile varies with the side slope angle was analyzed,then the force role and interface shear mechanism of anti-aging polypropylene(PP)staple needle-punched geotextile on landfill side slope was analyzed with engineering example,and the idea of preparing a kind of PTFE self-lubricating composite geotextile to reduce the tension in geotextile on the landfill side slope was proposed.The results showed that: the frictional angle of garbage soil/geotextile interface was greater than the frictional angle of geotextile/geomembrane interface and the difference of them was great,it was one of the main reasons for the geotextile was broken on the side slope of landfills caused by great tension.The interface shear force of garbage soil/anti-aging PP staple needle-punched geotextile was caused by relative motion and weak intermolecular attraction of the two contact surfaces.(2)The PTFE micropowder with good hydrophilicity and adhesion can be evenly dispersed in the water-borne resin emulsion and form strong bonding strength with the resin,to improve the lubricating property of the PTFE solid lubricating layer.Hence,based on the analysis of bonding property of PTFE surface,the trimethyl borate was used as surface modifier to improve the hydrophilic and cohesiveness of PTFE micropowder and its action mechanism was analyzed.Meanwhile,the effect of trimethyl borate modification on the lubricating property of PTFE solid lubricating layer was investigated.The results showed that:trimethyl borate and PTFE micropowder were bonded with coordination bond,and hydrolysis of trimethyl borate result in a large number of hydroxyl groups on the surface of PTFE micropowder,it could improve the hydrophilicity and cohesiveness of PTFE micropowder and the lubricating property of PTFE solid lubricating layer effectively.(3)The effects of concentration of trimethyl borate,solution temperature and treatment time on the hydrophilicity and surface element composition of modified PTFE micropowder was investigated,and the technological parameters of trimethyl borate-treated PTFE micropowder was optimized by orthogonal experimental method.The results showed that: the above three factors had great influence on the hydrophilicity and surface element composition of the modified PTFE micropowder,the hydrophilicity of modified PTFE micropowder was better according to the optimized technological parameters.(4)A PTFE self-lubricating composite geotextile was prepared with modified PTFE micropowder,water-based fluorocarbon resin emulsion and anti-aging PP staple needle-punched geotextile,and its surface/cross section morphology,mechanical properties and interface shear mechanism were analyzed.The results showed that: the effects of mass fraction of PTFE micropowder in lubricating layer and emulsion viscosity on frictional angle of the garbage soil/PTFE self-lubricating composite geotextile interface and surface morphology of PTFE self-lubricating composite geotextile were greater.Surface morphology of PTFE solid lubricating layer was good and its lubrication is obvious.The cross-section of it was composed of PTFE solid lubricating layer,transition layer and geotextile layer,and its tensile property met the application requirements.The interface shear force of garbage soil/PTFE self-lubricating composite geotextile was caused relative motion of the two surfaces rough peak,and the intermolecular attraction of the interface is almost zero.(5)Durability and anti-break reliability of PTFE self-lubricating composite geotextile,light resistance,acid and alkali resistance,oxidation resistance and metal ion resistance of garbage soil/PTFE self-lubricating composite geotextile interface frictional angle and its surface morphology was investigated.The effects of side slope angle and horizontal lateral pressure coefficient on the force of PTFE self-lubricating composite geotextile were investigated.The results showed that: its durability and anti-break reliability were better. |
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