ÜBERSICHT DER TESTS ZUR BODEN-BEWEHRUNG-INTERAKTION IN BEWEHRTEN BÖDEN DURCH PULLOUT-VERSUCHE

U radu su opisana dosadašnja dostignuća o modelskim istraživanjima armiranog tla pokusom izvlačenja armature iz tla. Ispitivanje izvlačenjem, vrlo značajno za karakterizaciju interakcije tla i armature, opisano je kroz pregled istraživanja koja su pridonijela spoznajama o interakciji i razvoju tehnike ispitivanja. Opisan je utjecaj rubnih uvjeta i drugih faktora na rezultate ispitivanja u pokusu izvlačenja. Prikazan je veliki uređaj za izvlačenje razvijen na Građevinskom fakultetu u Osijeku.A review of current knowledge on model studies of reinforced soil by pullout test is described in the paper. The pullout test, highly significant in soil-reinforcement characterisation, is described through a review of studies that have contributed to the characterisation of soil-grid interaction and development of testing techniques. The influence of test boundary conditions and other factors on pullout test results is described. The pullout testing apparatus developed at the Faculty of Civil Engineering in Osijek is presented.In dieser Arbeit werden vorhandene Kenntnisse bezüglich verschiedener Modellstudien an armierten Erdböden durch Ziehproben der Bewehrungen aus dem Boden beschrieben. Untersuchungen durch Pullout-Versuche, bedeutend für die Charakterisierung der Wechselwirkungen zwischen Boden und Bewehrung, sind durch eine Übersicht der Forschungen, die zu Einsichten in Bezug auf die Interaktion und die Entwicklung der Prüftechniken beigetragen haben, beschrieben. Der Einfluss von Randbedingungen und anderen Faktoren auf die Testresultate ist ebenfalls dargestellt. Ein Testgerät, das an der Fakultät für Bauwesen in Osijek entwickelt wurde, wird beschrieben

BESTIMMUNG DER BODENKONSISTENZ

Obrađuje se problem određivanja konzistentnog stanja koherentnog tla na temelju laboratorijskih i terenskih pokusa, te se uspoređuju odgovarajući postupci iz geotehničke prakse u Hrvatskoj i u svijetu. Predlaže se kategorije konzistentnog stanja tla vezati uz indeks konzistencije, a da kategorije određene na temelju nedrenirane čvrstoće tla označavaju kategorije krutosti tla. Predložen je mogući sustav kategorizacije konzistentnog stanja i krutosti tla za primjenu u Hrvatskoj.The problem of determining consistency of a coherent soil is analyzed based on laboratory and field testing and comparisons are made between practical geotechnical procedures used in Croatia and worldwide. According to the authors, the categories of soil consistency should be linked to consistency index, while categories determined according to the undrained strength of soil should denote categories of soil stiffness. A system for soil consistency and stiffness classification in Croatia is proposed.L’article étudie le problème de détermination de l’état de consistance d’un sol cohérent à partir des essais en laboratoire et in situ. On compare les procédés correspondants dans la pratique géotechnique en Croatie et dans le monde. Il est proposé que les catégories de l’état de consistance du sol soient liées à l’indice de consistance et que les catégories déterminées en fonction de la résistance non drainée du sol indiquent les catégories de la rigidité du sol. On propose un système de catégorisation de l’état de consistance et de rigidité du sol à mettre en oeuvre en Croatie.Behandelt ist das Problem der Bestimmung der Konsistenz von bindigen Böden auf Grund von Laborund Geländeuntersuchungen, weiter sind entsprechende Verfahren aus der geotechnischen Praxis in Kroatien und in der Welt verglichen. Es wird vorgeschlagen die Konsistenzkategorien mit dem Konzistenzindex zu verbinden, während die auf Grund der undrenierten Bodenfestigkeit bestimmten Kategorien Bodensteifigkeitskategorien bezeichnen. Für die Anwendung in Kroatien ist ein mögliches System derKategorisierung der Konsistenz und der Steifigkeit des Bodens vorgeschlagen

INFLUENCE OF THE RESPONSE OF A SHALLOW FOUNDED REINFORCED CONCRETE FRAME STRUCTURE ON SOIL LIQUEFACTION POTENTIAL

Nakon katastrofalnih posljedica potresa na Aljasci i u Niigati 1964. godine, Seed i Idriss su razvili i objavili metodu za procjenu otpornosti tla na likvefakciju pod nazivom „pojednostavljeni postupak“. Dugo vremena se smatralo kako prisutnost građevine smanjuje opasnost od pojave likvefakcije, no nakon nedavnih potresa (Kobe 1995. i Kocaeli 1999.) uočeno je kako se likvefakcija pojavila ispod temelja građevina, iako nije došlo do njezinog pojavljivanja na slobodnim površinama tla u okolici građevina. U ovome radu analiziran je i uspoređen likvefakcijski potencijal tla neopterećenog objektom i tla ispod građevine, za dva profila relativno mekog tla u Osijeku pri djelovanju dva potresa različitog frekventnog karaktera i magnitude. Linearno-elastične analize vremenskim zapisom provedene su koristeći računalni program SAP2000 za slučaj neopterećen objektom i za slučaj prisutnosti i utjecaja odziva plitko temeljene armiranobetonske okvirne konstrukcije. Dodatno su prikazani i osnovni dinamički odzivi same konstrukcije u interakciji s tlom, te je dana kratka usporedba s općeprihvaćenim modeliranjem apsolutno krutih oslonaca konstrukcije.Following disastrous earthquakes in Alaska and in Niigata in 1964, Seed and Idriss developed and published a method for evaluating liquefaction resistance of soils termed the ‘‘simplified procedure’’. For a long time it has been considered that the presence of the building reduces the risk of liquefaction, but after the recent earthquakes (Kobe 1995. and Kocaeli 1999.) it was observed that the liquefaction occurred under the foundations of buildings, although it has not been observed in the free field around buildings. This paper analyzes and compares soil liquefaction potential in the free field and beneath the building, for two relatively soft soil profiles under the influence of two strong motions with different frequency character and magnitude. A linear-elastic time history analysis was conducted using computer program SAP2000 for the free field case and case with presence and response impact of a shallow founded reinforced concrete frame structure. In addition, basic dynamic response of the structure in interaction with the soil is presented and a short comparison is made opposite to the widely accepted rigid-base structure assumption

NOSIVE PLATFORME ZA PRIJENOS OPTEREĆENJA : USPOREDBA PRORAČUNSKIH METODA

Constructing embankments on compressible foundation soil normally requires soil improvement measures to reduce the amount and duration of settlement. In the most difficult cases, the soil is improved by using pile foundations. When constructing pile foundations, it is necessary to ensure efficient load transfer from the embankment to the piles, which can be achieved using reinforced soil construction with geosynthetics as reinforcement material. In this paper, we compare the calculations of a bearing capacity of such a platform according to the British and the German standards on the example of a level crossing over a railway line. We describe other calculation methods, critically reviewing the fundamental mechanisms of the reinforcement effects in the calculations.Izvedba nasipa na stišljivom temeljnom tlu redovito zahtijeva mjere poboljšanja temeljnog tla kako bi se smanjio iznos i vrijeme slijeganja. Rješenje najtežih slučajeva postiže se upotrebom pilota. U slučaju izvedbe pilota potrebno je osigurati djelotvoran prijenos opterećenja od nasipa na pilote, što se može postići izvedbom platforme od armiranog tla koristeći geosintetike kao armaturu. U radu je prikazan proračun nosivosti ovakvih platformi i usporedba rezultata proračuna po dva standarda: britanskom i njemačkom, na primjeru cestovnog prijelaza preko željezničke pruge. Opisane su i ostale metode proračuna, uz kritički osvrt na način na koji se bitna svojstava korištene armature uvažavaju u proračunu

Selected results of determining the friction interaction coefficient between crushed stone and polyester strip

In the past twenty years in Croatia, a number of reinforced earth constructions have been built, of which two reinforced earth walls stand out due to their dimensions: Strikići and Sveta Trojica. In the building of these walls, polyester strips were used as reinforcement elements, whereas as fill material crushed stone aggregate was used. For designing these constructions, knowledge about the interaction mechanisms between the polyester strip and the soil is required. So far, most of the published studies have been directed to the determination of the friction interaction coefficient of the polyester strip and the fill material which was sand or gravel, whereas tests on the interaction between the geosynthetic strip and the crushed stone aggregate have not been performed. In order to determine the friction interaction coefficient between the crushed stone aggregate which is commonly used as fill material and the geosynthetic strip, pull-out tests of the polyester strip were carried out. Apart from pull-out tests, large direct shear tests were performed to determine shear strength parameters of crushed stone strength. Predictions from the numerical model were compared to a series of pull-out tests, proving that the numerical model provides reasonable predictions of pull-out behavior

Determination of soil consistency

Obrađuje se problem određivanja konzistentnog stanja koherentnog tla na temelju laboratorijskih i terenskih pokusa, te se uspoređuju odgovarajući postupci iz geotehničke prakse u Hrvatskoj i u svijetu. Predlaže se kategorije konzistentnog stanja tla vezati uz indeks konzistencije, a da kategorije određene na temelju nedrenirane čvrstoće tla označavaju kategorije krutosti tla. Predložen je mogući sustav kategorizacije konzistentnog stanja i krutosti tla za primjenu u Hrvatskoj.The problem of determining consistency of a coherent soil is analyzed based on laboratory and field testing and comparisons are made between practical geotechnical procedures used in Croatia and worldwide. According to the authors, the categories of soil consistency should be linked to consistency index, while categories determined according to the undrained strength of soil should denote categories of soil stiffness. A system for soil consistency and stiffness classification in Croatia is proposed

A review of soil and reinforcement interaction testing in reinforced soil by pullout test

U radu su opisana dosadašnja dostignuća o modelskim istraživanjima armiranog tla pokusom izvlačenja armature iz tla. Ispitivanje izvlačenjem, vrlo značajno za karakterizaciju interakcije tla i armature, opisano je kroz pregled istraživanja koja su pridonijela spoznajama o interakciji i razvoju tehnike ispitivanja. Opisan je utjecaj rubnih uvjeta i drugih faktora na rezultate ispitivanja u pokusu izvlačenja. Prikazan je veliki uređaj za izvlačenje razvijen na Građevinskom fakultetu u Osijeku.A review of current knowledge on model studies of reinforced soil by pullout test is described in the paper. The pullout test, highly significant in soil-reinforcement characterisation, is described through a review of studies that have contributed to the characterisation of soil-grid interaction and development of testing techniques. The influence of test boundary conditions and other factors on pullout test results is described. The pullout testing apparatus developed at the Faculty of Civil Engineering in Osijek is presented

PREGLED KRITERIJA ZA IZBOR GEOTEKSTILA ZA FILTAR

U radu se obrađuje primjena geotekstila za filtre i drenaže u geotehničkim i hidrotehničkim zahvatima. Analizirani su mehanizmi važni za dobro funkcioniranje geotekstila kao filtra koji se odnose na začepljenje, blokiranje i smanjenje pornog tlaka u zoni filtra. Na temelju raspoložive literature napravljen je pregled kriterija za izbor geotekstila kao filtra, u što su uvršteni i važeći nacionalni pravilnici. Prikazan je primjer definiranja kriterija za izbor geotekstila za filtar za ceste i za odlagalište otpada

PROCJENA EFIKASNOSTI GEOMREŽE U TLU JEDNOSTAVNIM POSTUPKOM

Modern geotehnical practice often uses technique of reinforced soil – a composite of soil and reinforcement – mostly geotextiles or geogrids. The efficiency of soil reinforcement depends on soil-reinforcement interaction, which can be determined by testing models in complex laboratory procedures. In this article simple and quick experiment designed to give assistance in determination of most effective geogrid for some granular soil, in lack of complex, expensive and time-consuming test procedures is presented. The idea of proposed test is determination of angle of soil repose, which represents soil friction angle at small vertical stresses and should be higher for reinforced soil than for non-reinforced soil. It is expected that for different grids different angle of soil repose is formed, so comparison of grid efficiency could be made. Tests results show soil-grid interaction, but with limited reliability and with limited application for practical purposes.Suvremena geotehnička praksa često koristi tehniku armiranog tla – kompozita tla i armature – najčešće goekstila ili geomreže. Efikasnost ojačanja tla ovisi o interakciji tla i armature, a ona se može utvrditi ispitivanjem modela u skupim laboratorijskim ispitivanjima. U ovom radu predstavljen je brz i jednostavan pokus koji je zamišljen kao pomoć u određivanju najprikladnije geomreže za neko nekoherentno tlo u nemogućnosti korištenja složenijih, skupljih i dugotrajnijih ispitivanja. Ideja predloženog ispitivanja je određivanje kuta rasprostiranja tla, koji predstavlja kut trenja tla pri malim naprezanjima i koji bi trebao biti veći za armirano tlo nego za nearmirano. Za očekivati je da je za različite mreže ovaj kut različit, što omogućuje međusobnu usporedbu efikasnosti geomreža. Provedena ispitivanja oslikavaju interakciju tla i mreže, no s ograničenom pouzdanošću i ograničenom primjenom za praksu

BEITRAG ZUR ANALYSE DER ANWENDUNG DES MARCHETTI-DILATOMETERS

U radu se opisuje princip ispitivanja dilatometrom Marchetti i interpretacije nekih parametara tla na temelju rezultata pokusa. Ispituje se utjecaj pogrešne prognoze pornog tlaka in situ u0 (NPV) na vrijednost interpretiranih parametara tla: tipa tla, nedrenirane čvrstoće i modula stišljivosti. Ustanovljeno je da je pogreška u interpretaciji navedenih parametara zbog krive procjene u0 zanemariva za preliminarne geotehničke analize. Istaknuta je opravdanost uporabe ovoga pokusa.The principle of Marchetti dilatometer testing procedure is presented and some soil parameters are interpreted on the basis of test results. Authors analyze the effect of faulty estimate of the in situ pore pressure u0 (NPV) on interpretation of soil parameters: type of soil, undrained strength and compressibility modulus. It was established that the error in interpretation of the above parameters, as resulting from erroneous u0 estimate, is negligible at the stage of preliminary geotechnical analyses. It is stressed that the use of this test is therefore justified.L’article décrit le principe des essais au dilatomètre Marchetti et les interprétations de certains paramètres du sol sur la base des résultats des essais. On étudie l’effet d’un pronostic erroné de la pression interstitielle in situ uo (NPV) sur la valeur des paramètres interprétés du sol : type de sol, de cohésion remaniée et de module de compressibilité. Il a été établi qu’une interprétation erronée de ces paramètres due à une mauvaise évaluation de uo était négligeable pour les analyses géotechniques préliminaires. On souligne la pertinence de l’utilisation de cet essai.Im Artikel wird das Prinzip der Untersuchung mit dem Marchetti-Dilatometer und die Interpretierung einiger Bodenparameter auf Grund der Experimentergebnisse beschrieben. Untersucht ist der Einfluss falscher Porenwasserdruckprognose in situ u0 (NPV) auf Werte der interpretierten Bodenparameter: Bodentyp, undrenierte Festigkeit und Zusammendrückbarkeitsmodul. Es wurde festgestellt dass der Fehler in der Interpretierung der gennanten Parameter wegen der falschen Abschätzung des u0 für präliminäre bodentechnische Analysen unterlässbar ist. Hervorgehoben ist die Berechtigung der Benützung dieses Experiments