Grunto, veikiamo periodinėmis apkrovomis, elgsenos tyrimai

Abstract

Straipsnyje yra apžvelgtos grunto liekamosios deformacijos ir įvertintas liekamasis grunto deformacijų modulis esant skirtingam grunto apkrovimų ciklų kiekiui. Šie tyrimai leidžia prognozuoti inžinerinio geologinio pagrindo, kuris perima apkrovas, elgseną esant skirtingam apkrovimo ciklų kiekiui (intensyvumui). Bandymai atlikti su triašio slėgio aparatu, imituojant automobilių kelių sukeliamas ir perduodamas apkrovas pagrindams. Gruntas ištirtas esant skirtingiems apkrovų intensyvumams ir grunto gyliams. Gauti rezultatai parodė, kad liekamasis grunto deformacijų modulis labai priklauso nuo grunto bandinio apkrovimo ciklų kiekio ir apkrovų intensyvumo. Nustatyta, kad bendrosios tirto grunto deformacijos nebuvo didesnės nei 2,0 %. Matuojant bandinio vertikalias defor-macijas ties bandinio viduriu, liekamosios deformacijos nebuvo didesnės nei 0,5 %. Gauti rezultatai yra labai vertingi prognozuojant / modeliuojant inžinerinio geologinio pagrindo elgseną esant skirtingam apkrovų ciklų kiekiui ir intensyvumui. Rezultatus galima lengvai pritaikyti tokio paties grunto sluoksnio skirtingiems gy-liams (įvertinti liekamąjį grunto sustiprėjimą).

This paper presents the results of a cyclic triaxial test on soil, namely gravely sand. These tests are very im-portant for the evaluation of engineering geological and geotechnical conditions when the strata is loaded with cyclic loads. The provided research work shows the resilient Young’s modulus change according to cy-cles quantity, stress deviator change and applied cell pressure. During the investigations, the constant cycles frequency (1 Hz) was applied. This frequency imitates moving road loads (moving car’s first and second axis load on road construction). Cycles quantity could be used for ranking materials on the basis of their plas-tic deformability. During this research it was obtained that investigated soil behaviour acts as stable deforma-tion behaviour (plastic shakedown). The conditioning phase was realised using stress deviator values from 10 to 200 kPa with total cycles quantity 20 000. Ana-lysing soil behaviour at the conditioning phase it was obtained that total sample deformation is less than 2.0% and resilient strain in the middle of the sample is less than 0.5%. According to characteristic permanent axial strain, investigated soil is classified as C3 class. The repeated loading phase was realised using stress deviators from 10 to 200 kPa with cell pressure from 20 to 70 kPa. Repeated loading for resilient testing showed that the resilient Young’s modulus depends on applied cell pressure and stress deviator minimum and maximum values. The investigated soil sample shape after tests was almost the same as before the tests. Obtained results are very valuable when it is neces-sary to evaluate soil behaviour under different cyclic loading and load stresses. Also, when repeated load-ing tests are provided with different cell pressures it is possible to imitate soil layer behaviour in different depths.