Kontroliuojamu slėgiu apkraunamo smėlinio grunto spūdumo tyrimas

Abstract

Nagrinėjamos Baltijos jūros pakrantės smėlio ties Klaipėdos pakrante spūdumo savybės, esant kontroliuojamam vertikalaus įtempio pokyčiui grunto bandiniuose. Spūdumo bandymai atlikti esant šiems apkrovimo greičiams: 25,0; 50,0; 100,0; 200,0; 400,0 ir 800,0 kPa/min. Spūdumo tyrimai atliekami su didžiausio poringumo bandiniais ir apspaudžiant iki 400,0 kPa apkrovos, kad nereikėtų vertinti struktūros ir atskirų dalelių irimo. Atliekant spūdumo bandymus su orasausiu natūralios sudėties gruntu, pastebėtas pridedamos apkrovos kitimas, kuris atsiranda dėl bandinį sudarančių dalelių tarpusavio persiskirstymo. Lyginant grunto spūdumo bandymų rezultatus su tokia pačia metodika apkraunamo gumos bandinio rezultatais, gumos bandinyje ženklių apkrovos kitimo šuolių nepastebėta.

This work presents experimental tests on typical Baltic sea-shore sand along Klaipėda. Natural sand was analyzed under laboratory conditions. The analysis is concentrated to an influence of load application velocities to vertical stress ramp. The analyzed values were: 25,0; 50,0; 100,0; 200,0; 400,0 and 800,0 kPa/min, respectively. The natural soil maximum void ratio was e = 0,798. The employed maximum vertical stress was 800,0 kPa at this investigation. At all test samples rating was 0,5 s. Obtained huge vertical stress ramp jump in all investigated loading speeds, when load was from 50,0 kPa to 120,0 kPa. For investigating the eventual reason of vertical stress jump was made analogous investigation with rubber sample. The rubber sample was loaded with ramp under 100,0 kPa/min. Then comparing the obtained results it was found that within bounds 50,0 to 120,0 kPa no any vertical stress ramp jump like in sand samples has been recognized. This finding can explain the sand compaction nature under loading. The sand compaction velocity is higher comparing with an applied vertical stress ramp. This subsequently causes the identified vertical stress jump. An equipment and infrastructure of Civil Engineering Scientific Research Center of Vilnius Gediminas Technical University was employed for investigation.