Laboratory testing of waste after biomechanical treatment

Prikazani su rezultati vlastitih laboratorijskih ispitivanja osnovnih geotehničkih karakteristika MBO otpada, koji su prethodili ispitivanju njegove stišljivosti u novom edometru, karakteristike ovog uređaja te priprema uzoraka i njihova ugradnja u edometarsku ćeliju. Prikazana je izrada novoga velikog edometra promjera 500 mm, visine 200 mm koji je neuobičajen za geotehnička ispitivanja u svijetu. Pored rezultata vlastitih istraživanja prikazani su i rezultati drugih autora.The authors present results obtained during laboratory testing of basic geotechnical properties of waste subjected to biomechanical treatment, as well as subsequent compressibility testing of this waste in a new oedometer. Properties of this oedometer, preparation of specimens, and their placement into the oedometer cell, are also presented. Fabrication of this new large-size oedometer, 500 mm in diameter, and 200 mm in height, seldom used in the world for the conduct of geotechnical tests, is described. In addition to their own test results, the authors also provide results obtained by other authors

Deformability of municipal waste after biomechanical treatment

Prikazana su ispitivanja mehaničkih svojstava mehaničko-biološki obrađenog (MBO) komunalnog otpada koja se bitno razlikuju od tih svojstava neobrađenog komunalnog otpada. Dani su rezultati ispitivanja stišljivosti, konsolidacije i propusnosti MBO otpada provedena u novom velikom edometru domaće proizvodnje. Uz podatke o vlastitim rezultatima istraživanja autori su dali i pregled objavljenih rezultata istraživanja drugih autora. Usporedba je pokazala dobro slaganje rezultata.The testing of mechanical properties of municipal waste subjected to biomechanical treatment is presented. These properties differ significantly from properties of municipal waste prior to such treatment. Results obtained by subjecting the biomechanically treated waste to the compressibility, consolidation and permeability testing, as conducted in the new big domestically-produced oedometer, are given. In addition to information about their own test results, the authors also present test results published by other authors. The comparison has revealed a good correspondence of results

Direct method for determination of shallow foundation settlements

Prikazan je direktan postupak za određivanje slijeganja plitkih temelja, koji kombinira modificiranu hiperbolnu funkciju za nelinearan odnos naprezanja i deformacija te korelacije iz rezultata penetracijskih pokusa. U korelacijama se koristi opterećenje za 10%, odnosno 1% omjera slijeganja i ekvivalentnog promjera temelja. Za ovaj novi postupak nisu potrebni laboratorijski pokusi, što je velika prednost za krupnozrna tla. Pokazuje se za ovako izračunane krivulje slijeganja u ovisnosti o opterećenju da je vrlo dobro poklapanje, s izmjerenim slijeganjima tijekom probnih opterećenja pet kvadratnih temelja različitih dimenzija na pijesku.A direct procedure for determining settlement of shallow foundations, combining the modified hyperbolic function for nonlinear stress and strain ratio with correlations from penetration test results, is presented in the paper. The 10% load, i.e. 1% of settlement to equivalent foundations diameter ratio, is used in correlations. Laboratory tests are not needed in this novel procedure, which is a considerable advantage for coarse-grained soils. A very good correspondence was established between the load-based settlement curve calculated in this way, and the settlements measured in sand during load testing of five square foundations of variable size

Quality control for rock anchors

U radu se opisuju laboratorijski pokusi čupanja štapnih sidara sa 48 raznih injekcijskih smjesa, uz mjerenje akustične emisije. Pokazuje se da se novim mjerenjem i predloženim analitičkim postupkom može odrediti sila koja je blizu sile sloma, tako da štapno sidro i dalje ostaje upotrebljivo za ojačanje stijenske mase. Mjerenje akustične emisije može se preporučiti za in situ kontrolu kvalitete štapnih sidara, uz novi doprinos kvaliteti aktivnoga geotehničkog projektiranja.Laboratory rock-anchor pullout test with 48 different grouts, and with the acoustic emission measurement, is described in the paper. It is demonstrated that the force close to the failure point can be determined by the new measurement and the proposed analytical procedure, so that the rock anchor will remain usable for rock mass strengthening purposes. Acoustic emission measurements can be recommended for the in situ rock anchor quality control, as a novel qualitative improvement of active geotechnical design practices

NUMERICAL MODELING OF SETTLEMENTS FOR SHALLOW FOUNDATIONS ON LAYERED SOILS

Numerička i empirijska metoda za proračun nelinearnih krivulja opterećenje-slijeganje za plitke temelje na pijesku ispitane su i primijenjene u novoj metodologiji. Obje metode imaju prednosti i nedostatke. Nedostaci su prevladani metodologijom predloženom i provjerenom u ovom radu. Ovom metodologijom kombiniraju se prednosti svake metode. U tu svrhu predlaže se promjena empirijske metode kojom se uzima u obzir konačna početna krutost tla pri vrlo malim deformacijama. Računalni programi sa složenim nelinearnim odnosima naprezanje-deformacija, kao što je Hardening Soil Small u Plaxisu 2D, koji su svestrani u rješavanju složenih problema s temeljima, mogu obuhvatiti deformacije od vrlo malih do velikih. Kad je temeljno tlo slojevito, predlaže se takvu numeričku krivulju opterećenje-slijeganje podesiti prema prilagođenom empirijskom odnosu za svaki sloj pijeska zasebno. To zahtijeva statičke penetracijske pokuse, mjerenja brzine posmičnih valova i osnovne laboratorijske pokuse. Metodologija je opisana i primijenjena na dvije lokacije na kojima su provedena probna opterećenja na temeljima. Na jednoj lokaciji nalazio se gornji sloj gline, što je također uzeto u obzir. Rezultati primjene predložene metodologije su vrlo dobri.A numerical and an empirical method for calculating nonlinear load-settlement curves for shallow foundations on sand are examined and used in a new methodology. Both methods have merits and drawbacks. The drawbacks are overcome by the methodology proposed and verified in the paper. This methodology combines the merits of each method. For this purpose, a modification of the empirical method is proposed that accounts for the finite initial soil stiffness at very small strains. Computer programs with sophisticated nonlinear stress-strain relationships, such as Hardening Soil Small in Plaxis 2D, which are versatile in solving complex foundation problems, can cover strains from very small to large. When the foundation soil is layered, it is proposed to fit such a numerical load-settlement curve against the modified empirical relationship for each sand layer separately. This requires cone penetration tests, measurements of the shear wave velocity, and basic laboratory tests. The methodology is described and applied at two locations where load tests on footings were carried out. At one location there was a top layer of clay, which was also taken into account. The results of the application of the proposed methodology are very good

CALIBRATION OF NUMERICAL MODELING AND A NEW DIRECT METHOD FOR CALCULATION OF SHALLOW FOUNDATION SETTLEMENTS IN SAND

U radu se razmatraju nelinearne metode za proračun slijeganja plitkih temelja u pijesku. Jedna od njih se oslanja na konstitutivni odnos Hardening Soil Small uključen u računalni program Plaxis 2D. Ona ima značajan nedostatak u potrebi modeliranja nepoznate povijesti deformacije temeljnog tla prije simuliranja pokusnog opterećenja na plitkom temelju. To se može prevladati predopterećenjem tla tlakom koji daje dobro slaganje između izračunatih i izmjerenih slijeganja. Međutim, na takav način nije moguće napraviti predviđanja slijeganja tla jer povijest deformacije tla nije unaprijed poznata. U radu se pokazuje kako se Plaxisom 2D mogu napraviti predviđanja slijeganja tla kalibracijom proračuna prema jednostavnoj izravnoj metodi. U skladu s ovom jednostavnom metodom razvijena je nova izravna metoda na temelju rezultata 16 pokusnih opterećenja izvedenih na 4 lokacije. Važna prednost ove nove metode je to što na odgovarajući način uzima u obzir ponašanje tla pri vrlo malim deformacijama.Nonlinear methods for calculation of shallow foundation settlements in sand are addressed in the paper. One of them relies on the Hardening Soil Small constitutive relationship incorporated in the computer program Plaxis 2D. It has a significant drawback in the need to model the unknown strain history of the foundation soil prior to simulating the load test on a shallow foundation. This can be overcome by preloading the soil with a pressure which gives good matching between calculated and measured settlements. However, predictions of soil settlements cannot be made in such a way, because the soil strain history is not a priori known. It is shown in the paper how predictions of soil settlements can be made by Plaxis 2D by calibrating calculations against a simple direct method. A new direct method is developed along the lines of this simple method, on the basis of results of 16 load tests performed at 4 locations. The important advantage of the new method is that it properly takes into account the soil behavior at very small strains