Stože Landslide – A Case History

The paper describes the Stože landslide that occurred in western Slovenia in November, 2000. It presents the landslide particularities and laboratory tests results. A numerical analysis of the slope failure was performed. It indicated the important role of the ground water level, and the dependence of slope stability upon it. Special laboratory equipment, a large-scale shear cell, was constructed in order to test the landslide material and to indicate the roles of the water content and loading velocities on the residual shear strength of material. A testing method is presented. It was assumed that the behaviour of material with a grain size of 4 mm or less could indicate the general behaviour of the landslide. Taking into account the possibility of an earthquake occurring in this region, attention was paid to the behaviour of this material at very small strains, and to the effect of different water contents and densities of the material. The deformation characteristics of reconstituted samples were investigated in a resonant column test at IST, Lisbon. Showing the influence of the water content and confining stress, empirical equations defining the small strain shear modulus have been proposed for different water contents

GEOLAB - Transnational Access project HSRTSUB - Resilient behaviour of stabilized and conventional high-speed's rail track subgrades under different drainage conditions and seat loads

In this study, the shear strength of track ballast material is evaluated by testing different types of track ballast specimens, which was conducted in a Large-scale Triaxial Apparatus at ZAG ) that has a shear area of 40 cm x 40 cm and can accommodate specimens up to 80 cm high. It enable loading of specimens in simple shear mode. The tests, which were conducted within HSRTSUB project, include two different types of ballast, the fouled ballast samples and the clean ballast samples, and two different specimen preparation techniques (with and without compaction). The normal stresses used cover a wide range from 50 to 400 kPa. The European standard EN13450 "Aggregates for railway ballast" was used. This standard specifies the properties of aggregates obtained by processing natural, manufactured or recycled crushed unbound aggregates for use in the construction of the upper layer of railway track. For the purposes of this standard, the aggregate is referred to as track ballast. Tests were conducted under unsaturated conditions with two types of lightweight materials: - fouled ballast aggregates and - clean ballast aggregate

GEOLAB - Transnational Access project LIWEMAT – Deformation characterisation of LIghtWEight foundation MATerials

Proper use of lightweight materials as construction material for various types of infrastructure brings a lot of advantages to European critical infrastructure related to weight reduction and prevention of progressive heating or freezing of its structural elements. Large-scale Triaxial Apparatus was used to perform the loading tests, which enables the characterization of materials at very small strain ranges with a very high accuracy level of load-displacement control. The apparatus has rigid confining aluminum frames with a height of 3 cm and cross-section of 40 x 40 cm, enabling prismatic specimens with a height of up to 80 cm to be tested. This research aims to determine the characteristics of expanded clay and foamed glass aggregates through laboratory testing, performing cyclic loading for the stiffness and damping evaluation, which would be beneficial parameters for numerical simulations. Testing material The foam glass aggregate has a homogeneous microstructure with approximate uniform shape and sizes. Foam glass aggregate is considered one of the best solid isolation materials with several unique properties. It can be widely used in many applications such as basement walls, foundations, floors and roofs, terrace and garden covers, rooftops, and parking areas. The expanded clay aggregate is round shape with different sizes with small, air-filled cavities, with dark brown, reddish, brown-red or gray colors, which depends on the chemical composition of the expanded clay. The lightweight expanded clay aggregate has bulk density from 250 kg/m3 to 710 kg/m3, mostly dependent on the size of the aggregate

Characterisation of ground thermal and thermo-mechanical behaviour for shallow geothermal energy applications

Increasing use of the ground as a thermal reservoir is expected in the near future. Shallow geothermal energy (SGE) systems have proved to be sustainable alternative solutions for buildings and infrastructure conditioning in many areas across the globe in the past decades. Recently novel solutions, including energy geostructures, where SGE systems are coupled with foundation heat exchangers, have also been developed. The performance of these systems is dependent on a series of factors, among which the thermal properties of the soil play one of major roles. The purpose of this paper is to present, in an integrated manner, the main methods and procedures to assess ground thermal properties for SGE systems and to carry out a critical review of the methods. In particular, laboratory testing through either steady-state or transient methods are discussed and a new synthesis comparing results for different techniques is presented. In-situ testing including all variations of the thermal response test is presented in detail, including a first comparison between new and traditional approaches. The issue of different scales between laboratory and in-situ measurements is then analysed in detail. Finally, thermo-hydro-mechanical behaviour of soil is introduced and discussed. These coupled processes are important for confirming the structural integrity of energy geostructures, but routine methods for parameter determination are still lacking

Odziv zasičenih zemljin na dinamično obremenitev

This paper presents the two most significant types of deformation behavior fordynamically loaded, saturated soil. Flow liquefaction and cyclic mobility deserve special attention because of the large deformations that accompany these two phenomena. The submergence of a railway-line embankment due to the newly built Sava-river accumulation reservoir in Boštanj and the large landslide that occurred in the Stože area in the Julian Alps are case histories in Slovenia where flow liquefaction and cyclic mobility were analyzed. The dynamic loading caused by railway traffic and possible seismic activity were taken into account. Material from these two sites, silty sand and lacustrine carbonate silt, were used in extensive laboratory research, with the objective to define a procedure for excess pore-water pressure-generation modeling in dynamically loaded saturated soil. It has been found recently that the change of the pore-water pressure is related to the dissipated energy density calculated from the hysteresis loops caused by dynamic loading. Based on the experimental results an empirical equation defining the generation of pore pressure during dynamic loading has been proposed. The equation is divided into two parts: the first part describing the residual pore-water pressure generation, and the second part describing the increment and decrement of pore-water pressure within the load cycle, the so-called temporary pore-water pressure change. The proper effective stresses and thus the stress path of the dynamically loaded soil can be defined by using the proposed energy-based numerical model. The proposed pore-pressure model can also be used in deformation-behavior modeling. It was observed from the experimental results that after a few cycles of dynamic loading the saturated soil starts to exhibit a very low stiffness at the beginning of a load cycle, after which it begins to strengthen. The strain developed during this softening phase represents the main share of the total strain. The occurrence and duration of this phase are related to the energy dissipated during the cyclic loading as well, and the relation between the dissipated energy, the excess pore pressure and the short-term flow during cyclic mobility, give us an opportunity for a simple response modeling of the dynamically loaded saturated soils.V članku sta predstavljena dva najbolj izrazita načina deformiranja dinamično obremenjenih zasičenih zemljin. Likvifakcija s tečenjem in ciklična mobilnost sta pojava, ki pritegneta posebno pozornost zaradi velikih deformacij, ki ju spremljajo. Potopitev nasipa železniške proge zaradi novozgrajenega akumulacijskega bazena na reki Savi v Boštanju in velik plaz, ki se je sprožilna področju Stože v Julijskih Alpah predstavljata študiji primerov v Sloveniji, kjer sta bili analizirani tudi likvifakcija s tečenjem in ciklična mobilnost. Upoštevana je bila dinamična obremenitev zaradi železniškega prometa in morebitne potresne obtežbe. Materiali iz obeh lokacij: meljni pesek in prodnato-peščeni melj, so bili uporabljeni v obsežnih laboratorijskih preiskavah, katerih namen je bil določiti postopek za modeliranje generiranja dodatnega pornega pritiska v dinamično obremenjenih z vodo zasičenih zemljinah. Novejše ugotovitve kažejo, da je sprememba pornega tlaka povezana s količino disipirane energije, ki jo določajo histerezne zanke dobljene z dinamičnim obremenjevanjem. Na osnovi eksperimentalnih rezultatov je bila predlagana enačba za empirično zvezo, ki definira generiranje pornega tlaka med dinamičnim obremenjevanjem. Enačba je sestavljena iz dveh delov, prvi opisuje generiranje nepovratnih sprememb pornega tlaka, drugi del pa opisuje prirastke in upade tlaka porne vode znotraj enega obremenjevalnega cikla, ti. povratne spremembe pornega tlaka. Z uporabo predlaganega energijskega numeričnega modela je mogoče določiti dejanske efektivne napetosti in s tem napetostno pot dinamično obremenjene zemljine. Predlagani model za porne tlake se lahko uporabi tudi za modeliranje deformacijskega obnašanja. Z eksperimenti je bilo ugotovljeno, da ima dinamično obremenjena zemljina po nekaj ciklih obtežbe na začetku cikla zelo nizko togost, ki pa se kasneje poveča. Deformacija, ki se razvije za časa trajanja te podajne faze zemljine, predstavlja glavnino deleža skupne deformacije. Pojav in trajanje te faze sta prav tako povezana z energijo, ki se disipira med cikličnim obremenjevanjem. Odnos med disipirano energijo in dodatnim pornim tlakom ter kratkotrajnim tečenjem med pojavom ciklične mobilnosti, omogoča preprosto modeliranje odzivadinamično obremenjenih zasičenih zemljin

Potencial ciklične likvefakcije jezerske krede in Julijskih alp

This paper presents the liquefaction studies of lacustrine carbonate silt from the Julian Alp landslide Stože. Geological conditions of the region and geomechanical characteristics of the ground were investigated. The research project was performed with the intention to determine the effects of cyclic loading on lacustrine carbonate silt. Investigation with 77 cyclic triaxial tests was performed on universal triaxial apparatus Wykeham Farrance UP 100 TR, in the Laboratory of soil mechanics, Faculty of Civil Engineering, University of Maribor. The essential equipment comprises cylindrical triaxial apparatus with a cell, a press with appurtenant electro-mechanic equipment, measuring equipment, and computer hardware and software equipment. Specimens with dimensions of height = 140 mm and diameter = 70 mm were saturated, then subjected to the arbitrary initial isotropic stress state and consolidated with vertical and radial draining, and then loaded with distortional loading of chosen dynamical axial force (frequency f = 1 Hz). A set of tests with a spectrum of different stress states and cyclic loading were performed. This research showed that lacustrine carbonate silt is a highly sensitive material.The resistance to liquefaction was somewhat higher than that of typical clean sand, but a perceivable excess pore pressure generation, which causes the decrease of strength parameters, was noticed. Test results of cyclic triaxial tests indicate dynamic characteristics of lacustrine carbonate silt and wide applicability of the test method.Prispevek podaja rezultate ciklične triosne preiskave kompozita prodnato peščenega melja jezerske krede iz območja plazu Stože v Julijskih Alpah. Namen preiskave je bil določitev nekaterih statičnih in dinamičnih lastnosti obravnavanega melja pri različnih (izbranih) pogojih in dinamičnih vplivih. Obravnavan je likvifakcijski potencial, t.j. možnost (verjetnost) utekočinjenja materiala zaradi izničenja njegove strižne trdnosti, pri naraščanju pornega vodnega tlaka v zemljini, zaradi ciklične obtežbe. Na območju plazu so bile pred tem opravljene obsežne geološke in geotehnične raziskave. Za določitev dinamičnih lastnosti so bile izvedene terenske preiskave, ki so vsebovale seizmične refrakcijske meritve in meritve hitrosti seizmičnih valov z “down-hole” metodo ter laboratorijske preiskave, ki so med drugim vsebovale tudi resonančni preizkus in ciklično torzijsko preiskavo. Pri preiskovanem materialu je za geotehnične analize ključnega pomena preučevanje fenomena likvifakcije. Namen pričujoče preiskave je bil pripravljene vzorce prodnato peščenega melja pri različnih pogojih privesti do likvifakcije s cikličnim obremenjevanjem, ter iz odziva na dinamične vplive podati zakonitosti likvifakcije. Podani so odnosi med številom ciklov potrebnih za likvifakcijo, začetnim stanjem materiala in pogoji obremenjevanja. V Laboratoriju za mehaniko tal, na Fakulteti za gradbeništvo, Univerze v Mariboru, je bila izvedena preiskava s 77 cikličnimi triosnimi preizkusi. Za preiskavo je bil uporabljen Univerzalni triosni aparat Wykeham Farrance UP 100 TR. Preizkusi so bili izvedeni na valjastih preizkušancih višine 140 mm in premera 70 mm. Vsak preizkušanec je imel enake začetne fizikalne lastnosti, z minimalnim odstopanjem vrednosti. Izvedena je bila saturacija, do stanja popolnega zasičenja (po kriteriju B>0.96). Sledila je faza konsolidacije pri izbranem napetostnem stanju in omogočenem bočnem dreniranju. Naslednji korak je bila izvedba nedreniranega cikličnega preizkusa z izbrano vertikalno ciklično obtežbo, s frekvenco 1 Hz. Med preizkusom so bile merjene časovne spremembe vertikalne napetosti σd(t), vertikalne deformacije εa(t), in porni vodni tlak uw(t). V preiskavi so bili spreminjani naslednji pogoji: začetne efektivne napetosti σ0’, količnik por ec in faktor obremenitve CSR, v naslednjih mejah: σ0’ = 50, 100, 150 in 200 kPa, ec = 0,320 ÷ 0,490 in CSR = 0,15 ÷ 0,30. Rezultati preiskave nakazujejo občutljivost jezerske krede. Odpor na likvifakcijo je sicer višji kot pri tipičnih čistih peskih, vendar so opazni prirastki pornega tlaka in upad parametrov trdnosti

Dynamic properties of lightweight foamed glass and their effect on railway vibration

Deformation properties of lightweight coarse grained material from recycled foamed glass have been determined from large-scale triaxial tests on prismatic specimens with dimensions 40 cm × 40 cm × 80 cm. Deformations were measured locally using vertical and horizontal local deformation transducers. Monotonic and cyclic loading at small to medium strain range were conducted. Three load sequences representing the expected conditions of use of lightweight material as vibration-reducing material in railway geotechnics have been used. Results indicate strong effect of brittle cellular structure of tested material as well as confining pressure dependency of elastic threshold shear strain and damping ratio. The results were used to assess the applicability of empirical formulas for shear modulus of granular materials to lightweight foamed glass. The parameters determined from the laboratory tests were further used in numerical analysis of railway dynamic response. The results of the numerical simulations show that replacement of fill in track embankment by lightweight material could improve the dynamic response of the track in reducing the vibration.Dynamic properties of lightweight foamed glass and their effect on railway vibratio

Utekočinjenje tal v porečju reke Tone med potresom ob vzhodni obali Japonske 2011

A brief report about the liquefaction damage in the Tone river basin, caused by the 2011 earthquake off the Pacific coast of Tohoku, is presented. It includes sand boiling, damage to river dikes, the settlement and tilt of superstructures, the uplift of light underground structures and lateral spreading. A history of land reclamation along the Tone river is briefly presented to understand why extensive liquefaction took place predominantly inreclaimed land. The recorded ground motions near the river were analyzed andcompared to near-source ground motions. The effects of the site location and the ground conditions during the peak ground acceleration are discussed.Članek na kratko poroča o primerih utekočinjenja tal v porečju reke Tone zaradi potresa ob vzhodni obali Japonske leta 2011. Predstavljeni so primeri pojava kipečih peskov, poškodbe na rečnih nasipih, posedki in nagibanja objektov, dvižki lahkih podzemnih objektov in bočno razrivanje površja. Za lažje razumevanje vzrokov pojava velikega števila primerov utekočinjenja tal na melioriranih področjih, je na kratko predstavljena zgodovina poteka melioracij ob reki Tone. V članku so presojani zapisi premikov tal na območju reke. Izvedena je njihova primerjava s premiki iz območij bližje žarišču potresa. Prispevek razpravlja tudi o vplivih lokacije in sestavi tal na največje pospeške temeljnih tal

Using recycled material from the paper industry as a backfill material for retaining walls near railway lines

The construction industry uses a large amount of natural virgin material for different geotechnical structures. In Europe alone, 11 million tonnes of solid waste is generated per year as a result of the production of almost 100 million tonnes of paper. The objective of this research is to develop a new geotechnical composite from residues of the deinking paper industry and to present its practical application, e.g., as a backfill material behind a retaining structure. After different mixtures were tested in a laboratory, the technology was validated by building a pilot retaining wall structure in a landslide region near a railway line. It was confirmed that a composite with 30% deinking sludge and 70% deinking sludge ash had a high enough strength but experienced some deformations before failure. Special attention was paid to the impact of transport, which, due to the time lag between the mixing and installation of the composite, significantly reduced its strength. The pilot retaining wall structure promotes the use of recycled materials with a sustainable design, while adhering to government-mandated measures

Some experience in numerical modelling of unsaturated slope instabilities

In the past couple years, the region of South-East Europe is subjected to gust rainfall events activating many landslides which cause significant material and human losses. To revaluate the existing risk maps and set new standards some old case histories are revaluated. This paper presents two case histories of landslide instabilities subjected to excess climatic perturbations, gust rainfall, namely the «Stanjevci» cut-slope near the railway line in North-East of Slovenia; and the «Ramina» a natural landslide in urban area near the city of Veles in Central Macedonia. They are briefly described later to be analysed using coupled thermo-mechanical calculations. They are subjected to specific short and gusting rainfall considered as possible trigger. Hence, van Genuchten’s hydraulic model is used in combination with elastoplastic material models. The results are summarized with critical comments regarding the mathematical formulation used to describe atmospheric-soil interaction and the influence of different aspects on the accuracy is discussed briefly