Available online at ScienceDirect. Procedia Engineering 172 (2017 )

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1 Aville online t ScienceDirect Procedi Engineering 172 (2017 ) Modern Building Mterils, Structures nd Techniques, MBMST 2016 Experimentl nd Numericl Anlysis of Direct Sher Test Nering Dirgėlienė *, Šrūns Skuodis, Andrius Grigusevičius Deprtment of Geotechnicl Engineering, Deprtment of Structurl Mechnic, Vilnius Gedimins Technicl University, Sulėtekio l. 11, Vilnius LT-10223, Lithuni Astrct An experimentl nd numericl investigtions of the direct sher test hve een performed under constnt verticl stress (q = const) nd constnt smple volume (h = const). During the determintion of soil sher strength in lortory y different test methods soil is loded in different wy. This fct hs n influence on stress-strin distriution in the smple. The finite-element method nlysis lso shows tht during direct sher tests distriution of stress nd strin in the smple is non-uniform. If we know rel distriution of stress nd strin in the smple, it is possile to determine the soil sher strength nd deformtion prmeters in more precise wy or to rte the influence of different fctors on soil properties The Authors. Pulished y Elsevier Ltd. This is n open ccess rticle under the CC BY-NC-ND license 2016 The Authors. Pulished y Elsevier Ltd. ( Peer-review under responsiility of the orgnizing committee of MBMST Peer-review under responsiility of the orgnizing committee of MBMST 2016 Keywords: direct sher test; finite-element method, constnt verticl stress; soil constnt volume; stress-strin distriution. 1. Introduction Sher strength is the principl engineering property of soil, which controls the stility of soil mss under structurl lods. Accurte determintion of the soil sher strength prmeters (ngle of internl friction nd cohesion) is mjor interest in the design of different geotechnicl structures. These prmeters cn e determined either in the lortory or in the site. The trixil compression nd direct sher tests re the most common tests for determining the ngle of internl friction nd cohesion vlues in the lortory. Specil cre must e tken to estlish loding condition ctully existing in the ground nd to duplicte this condition in the lortory. * Corresponding uthor. Tel.: ; fx: E-mil ddress: Nering.Dirgeliene@vgtu.lt The Authors. Pulished y Elsevier Ltd. This is n open ccess rticle under the CC BY-NC-ND license ( Peer-review under responsiility of the orgnizing committee of MBMST 2016 doi: /j.proeng

2 Nering Dirgėlienė et l. / Procedi Engineering 172 ( 2017 ) Boundry conditions re not distinct when nlysing soil smples y direct sher test [1]. Not ll verticl stress pllied on top of sher ox specimen is trnsmitted on soil. It is not ovious the regulrity of chnge of norml stresses on sher plne [2 6]. If direct sher test is nlysed, the stress distriution depends on the following: mnner of verticl lod trnsmission, position of the moile prt of sher ring, horizontl displcement of the moile prt of the ring. Some fctors re not evluted during the results interprettion, for exmple, friction etween soil nd device metl prts [3,7 10]. The numericl methods enle the determintion of mteril prmeters tht would hve een difficult to mesure in the experimentl study [4,5,11]. The im of the current investigtion is to nlyse stress-strin distriution in the smple during direct sher testing depending on the mnner of the verticl lod trnsmission. The experimentl direct sher test on snd hve een performed under constnt verticl stress (q = const) nd constnt smple volume (h = const). Experiments were simulted performing the numericl nlysis y finite element method progrm COSMOS/M. 2. Lortory experiments The ir-dry snd of the Bltic Se costl re ws used to perform the experiments for determining the sher strength prmeters. The verge density of prticles (ρ s) vlue of mrine snds is 2.66 Mg/m³ nd rnges from 2.65 to 2.67 Mg/m³ [9]. The verticl stress mgnitudes of 100, 200, 300 kp hve een pplied. The soil is shered under the constnt horizontl displcement velocity of 0,5 mm/min until the horizontl deformtion reches the limit of 9 mm. The sher test is performed under two different cses (methods), nmely: when constnt verticl stress (q = const.) is pplied; when constnt smple volume (h = const.) is pplied. The sher tests hve een performed for loose snd (density ρ = 1,491 g/cm 3 ). The pek soil shering strength hs een determined ccording to the mximum rtio of tngentil nd norml stresses, id est. ccording τ/σ = mx [9]. 3. Anlysis of otined results The chrcteristic investigted snd sher grphs for loose soil (Figs. 1 2) hve een processed for different testing methods, id est. for q = const nd h = const [9]. In the cse of initilly loose snd when q = const there is no significnt prticle interlocking to e overcome nd the tngentil stress increses grdully to n ultimte vlue without prior pek, ccompnied y decrese in volume (Fig. 1 ). In the cse h = const sher stress increses nd decreses immeditely nd fter remins lmost stedy (Fig. 1 ). Fig. 1. Tngentil stress t the pplied norml stress when: ) q = const; ) h = const. From Fig. 2 one cn find tht the pplied verticl stress of mgnitudes of 100, 200, 300 kp remined constnt during ll the test time. Aiming to keep the constnt smple volume t the eginning of testing, the verticl loding

3 220 Nering Dirgėlienė et l. / Procedi Engineering 172 ( 2017 ) primrily hs een reduced wheres tngentil stress hs een incresed. Lter during shering the verticl stress ws decresed iming to constrin the smple contrction in verticl direction. Simultneously tngentil stress ws decresed (Fig. 2 ). Fig. 2. Stress pths under constnt verticl stress condition: ) q = const ) h = const. 4. Numericl nlysis of soil smple during direct sher test A numericl modelling ws crried out y finite element method progrm COSMOS/M. Liner nlysis ws ssumed to simulte the elstic ehviour of snd. The ccepted prmeters of smple: elsticity modulus 20 MP, Poisson s rtio 0,3, mss density 1,491 Mg/m 3. The smple, 7,14 cm in dimeter nd 3,39 cm in height, ws discretised into tetrhedrl elements. Two principl digrms were designed: 1) in the first cse verticl pressure 400 kp (s in experiment q=const) cts on the top of the model (the displcement of the smple top surfce nodes re free in verticl direction), the nodes of upper lterl wlls of smple re free in verticl direction, the nodes of lower lterl wll of smple re free in verticl nd horizontl directions nd plne of ottom re free in horizontl direction; 2) in the second cse displcement uniformly cts verticlly u y=const (2 mm) on the top surfce of the smple (the displcement of the smple top surfce nodes re free in verticl direction), the nodes of upper lterl wll re free in verticl nd lower lterl wlls of smple re free in verticl nd horizontl directions, the nodes of ottom plne re free in horizontl direction. The results of numericl modeling re shown in Figs Appliction of verticl lod (Fig. 3 ) shows, tht verticl stress distriution on the smple top is uniform when q = const (Fig. 4 ), nd in the shering plne otined smller verticl stress (Fig. 5 ). The sher plne is loded y ~95 % of the totl verticl lod. In the second cse when u y=const t the eginning of the test verticl stress is not uniform on the smple top (Figs. 3, 4 ). In the smple sides the verticl stress is higher ~9 % thn in the smple center on the soil top, the verticl stress t the sher plne is distriuted non-uniform similrly in cse q = const (Fig. 5 ). The verticl displcements when cts only verticl stress re showed in Figs. 6,. The verticl displcements distriution on the smple top (Fig. 7, ) nd t the rings prts interfce (Fig. 8, ) re lmost smooth in oth loding cse. In the cse when constnt verticl loding (q = const) nd horizontl displcement (5 mm) re pplied, otined verticl stress on the smple top is higher out 8 % in the left side thn in the right side of the soil smple (Figs. 9, 10 ). Anlyzing u y=const cse we see contrry results, the verticl stress on the smple top is higher out 54 % in the right side thn in the left side of the soil smple (Figs. 9, 10 ). When q=const t the rings prts interfce we cn see the soil in the right side of the smple is lifted, nd in the contrry side the soil moves down (Fig. 11 ). In cse u y = const stress distriute lmost uniform (Fig. 11 ). Verticl displcements on smple top when verticl lod nd horizontl displcement re pplied in cse q = const hs smll difference (Figs. 12, 13 ), in cse u y = const re uniform (Figs. 12, 13 ). The verticl displcements distriutes lmost eqully on the smple top in oth cses. In oth loding cses the verticl displcements on the interfce of rings prts re similr (Figs. 14, 14 ).

4 Nering Dirgėlienė et l. / Procedi Engineering 172 ( 2017 ) Fig. 3. Verticl stress when cts only verticl lod: ) q = const; ) u y=const. Fig. 4. Verticl stress distriution on the smple top when cts only verticl stress: ) q = const, ) u y=const. ) Fig. 5. Verticl stress distriution on the interfce of smple prts when cts only verticl lod: ) q = const, ) u y=const.

5 222 Nering Dirgėlienė et l. / Procedi Engineering 172 ( 2017 ) Fig. 6. Verticl displcements when cts only verticl stress: ) q = const, ) u y=const. Fig. 7. Verticl displcements distriution on the smple top when cts only verticl stress: ) q = const, ) u y=const. Fig. 8. Verticl displcements distriution on the interfce etween ring prts when cts only verticl lod: ) q = const, ) u y=const.

6 Nering Dirgėlienė et l. / Procedi Engineering 172 ( 2017 ) Fig. 9. Verticl stress when verticl stress nd horizontl displcement re pplied: ) q = const, ) u y=const. Fig. 10. Verticl stress on the smple top when verticl stress nd horizontl displcement re pplied: ) q = const, ) u y= const. Fig. 11. Verticl stress on the interfce etween rings prts when verticl stress nd horizontl displcement re pplied: ) q = const, ) u y=const.

7 224 Nering Dirgėlienė et l. / Procedi Engineering 172 ( 2017 ) Fig. 12. Verticl displcements when verticl stress nd horizontl displcement re pplied: ) q = const, ) u y=const. Fig. 13. Verticl displcements on smple top when verticl stress nd horizontl displcement re pplied: ) q = const, ) u y=const. Fig. 14. Verticl displcements on the interfce of smple prts when verticl stress nd horizontl displcement re pplied: ) q = const, ) u y=const.

8 Nering Dirgėlienė et l. / Procedi Engineering 172 ( 2017 ) Conclusions During the direct sher tests the soil is loded in different wy, it hs n influence on stress-strin distriution in the smple. Not ll pplied verticl stress on the top of smple is trnsmitted to the sher plne. In the cse when constnt verticl loding (q = const) nd horizontl displcement (5 mm) re pplied otined verticl stress on the smple top is higher out 8 % in the left side thn in the right side of the soil smple. Anlyzing u y=const cse we see contrry results, the verticl stress on the smple top is higher out 54 % n the right side thn in the left side of the soil smple. Acknowledgement An equipment nd infrstructure of Civil Engineering Scientific Reserch Center of Vilnius Gedimins Technicl University ws employed for investigtions. References [1] S. Heng, H. Oht, T. Piptpongs, M. Tkemoto, S. Yokot, Constnt-volume direct ox-sher test on cly-sem mterils, in: Proc of the 17th Southest Asin Geotechnicl Conference, My 10 13, Tipei, Tiwn, 2010, pp [2] C. Thornton, L. Zhng, Numericl Simultions of the Direct Sher Test, Chemicl Engineering &Technology 26(2) (2003) [3] V. Kostknov, I. Herle, Mesurement of Wll Friction in Direct Sher Tests, Act Geotechnic (2012) [4] R. Ziie Moyed, S. Tmssoki, E. Izdi, Numericl Modeling of Direct Sher tests on Sndy Cly, Interntionl Journl of Civil, Environmentl, Construction nd Architecturl Engineering 6(1) (2012) [5] D.H. Kng, J. Choo, T. S. Yun, Evolution of pore chrcteristics in the 3D numericl direct sher test, Computers nd Geotechnics 49 (2013) [6] A. Amšiejus, N. Dirgėlienė, A. Norkus, Š. Skuodis, Comprison of sndy soil sher strength prmeters otined y vrious construction direct sher pprtuses, Archives of Civil nd Mechnicl Engineering 14(2) (2014) [7] C. O Sullivn, L. Cui, J.D. Bry, Three-Dimensionl Discrete Element Simultions of Direct Sher Tests. In: 2 nd Interntionl PFC Symposium, , Kyoto, Jpn. [8] S.H. Liu, D.A. Sun, H. Mtsuok, On the interfce friction in direct sher test, Computers nd Geotechnics 32(5) (2005) [9] Š. Skuodis, A. Norkus, N. Dirgėlienė, A. Kvrus, Snd shering peculirities using direct sher device, Procedi Engineering 11th interntionl conference on modern uilding mterils, structures nd techniques, My 16-17, 2013, Vilnius, Lithuni. Amsterdm: Elsevier Science Ltd, ISSN , pp [10] K. Thermnn, C. Gu, J. Tiedemnn, Sher strength prmeters from direct sher tests influencing fctors nd their significnce, in: Interntionl Assocition For Engineering Geology nd the Environment: Engineering Geology for Tomorrow's Cities, 10th, 2006, Nottinghm: The Geologicl Society of London. [11] J.M. Royo, S. Melentijevic, Comprison of lortory direct sher test results with the numericl nlysis, Numericl Methods in Geotechnicl Engineering Hicks, Brinkgreve&Rohe (Eds), London: CRC Press, 2014, pp