Effect Of Bentonite On Dynamic And Static Mechanical Properties Of Cemented Backfill

It has always been a uneasy problem to be resolved in the mine for filling technology.Which is the unconnected filling rate of mine filling.The addition of expansion agent in the filling slurry can increase the filling rate to reach to top to a certain extent,but the filling body in the mine will be impacted by high-speed loads.And the filling body impacted at high speed is prone to instability and damage.In this paper,the dynamic load and uniaxial compression tests of the bentonite-filled body were carried out using the split Hopkinson pressure bar test system and the RMT-150 c rock mechanics test system.Which aims to study the effects of bentonite under dynamic loading and static loading on the mechanical properties of the filling body.The resoults can provide theoretical guidance for the using of bentonite for mine filling and capping.The specific research contents are as follows:(1)Uniaxial compression experiments of various bentonite(0,5%,10%,15%)fillings at different curing days(3,7,14,28 days)were done applying the RMT-150 c rock mechanics test system.The experimental results indicate that the velocity of longitudinal wave,compressive strength and elastic modulus of the filling body are allmostly the same law as the curing day,which increases with the rise of the curing age.And these are fourteen days before the curing age.The parameters grow faster with the days of curing,and the growth rate slows down after fourteen days of age.The variation of longitudinal wave velocity,compressive strength and elastic modulus of the filling body with the amount of bentonite is basically the same.When the content of bentonite is 0~10%,these mechanical parameters of the filling body decrease with the rise of the amount of bentonite,but when the content of bentonite is 10%~15%,these parameters of the filling body increased.(2)The SHPB test system was applied to conduct a single impact test both on the equal incident energy at different fillings with various bentonites dosage.The experimental results demonstrate that whether the bentonite is in or not the filling,all the dynamic compressive strength of the filling body increases while the growth of the curing days,and the growth curve can be perfectly fitted by the exponential function.The dynamic elastic modulus of the filling body rises with the growth of the curing day,but the growth rate is more slowly before the curing age of fourteen days.After the dynamic load,the absorption energy of the filling body gradually increases with the growth of the curing days,and which is maintained in all the filling.Before the curing age of fourteen days,the growth rate of absorption energy is faster,and then the growth rate slowed down a lot.The dynamic compressive strength of filling,dynamic elastic modulus of filling and absorption energy of the filling body are consistent with the various of bentonite content of filling.These are the kinetic parameters of the filling body with the increase of bentonite.When the content of bentonite in filling is 0~10% gradually decrease,but while the amount of bentonite increased from 10% to 15%,these kinetic parameters of the filling body will have a certain increase.(3)The cyclic impact test of fillings with different bentonite contents in thirty days of curing period was carried out to study dynamic properties of the filling.The final experimental results show that under the cyclic impact of the same incident energy,the filling body with amount of bentonite is damaged more quickly.Under repeated impact,the macrofailure mode of cemented filling with bentonite is first peripheral damage,then crack,and finally crack propagation until failure.