Skenaariolaskelmia työn muutoksen vaikutuksesta eläkejärjestelmään ja julkiseen talouteen

Raportissa käsitellään työn muutoksen vaikutuksia eläkejärjestelmän ja koko julkisen talouden näkymiin skenaariolaskelmien avulla. Kolme skenaariota perustuvat Demos Helsingin raporttiin ”Työ 2040 – Skenaarioita työn tulevaisuudesta”. Nämä skenaariot ovat ”kunnialliset puurtajat”, ”taipuisat tekijätyypit” sekä ”taikurien talous”. Neljäs skenaario on nimeltään ”korkea työllisyys” ja se perustuu julkisuudessa esitettyyn ajatukseen jopa 80 prosentin työllisyysasteen tavoittelemisesta. Skenaarioiden erityispiirteitä ovat talouskasvun pysähtyminen, yrittäjyyden lisääntymistä, tuloerojen kasvu ja korkea työllisyys. Jokaisesta skenaariosta esitetään Eläketurvakeskuksen pitkän aikavälin suunnittelumallin avulla tehtyjä laskelmia. Osasta skenaarioita esitetään Eläketurvakeskuksen ELSI-mikrosimulointimallilla tai valtiovarainministeriön kestävyysvajeen laskentakehikolla tehtyjä laskelmia

Excavation damage zone fracture modelling for seismic tomography : a comparison of explicit fractures and effective medium approaches

We model the full wavefield produced by a seismic velocity survey and optimise the representation of the fracture zone to best match field waveforms. The velocity survey was part of a mapping study on fractures in the Excavation Damage Zone (EDZ) of ONKALO underground research facility at Olkiluoto. The EDZ results from excavation of the rock mass, which modifies stress conditions changing the nature and behaviour of pre-existing fractures and generating new fracturing. These fractures act as the main transport pathways for contaminants both in and out of a geological disposal facility (GDF). Our goal is to test different representations of the fracture zone and to determine which models most successfully improve the interpretation of the fracture zone, producing estimates of a key unknown parameter, fracture stiffness, in addition to fracture sizes, fracture geometry, fracture density and crack density. We use modelling techniques previously tested in theoretical and laboratory studies and assess their performance on a real engineering problem. The paper introduces the field experiment and relevant information from the GDF in Finland. It describes the methodologies used for representing the fracture networks in the models — Explicit Fracture models with two approximations called Pixelised Fracture Model (PFM) and Equivalent Discrete Fracture Medium (EDFM), the Effective Medium (EM) model, and two versions of the Localised Effective Medium (LEM) model (LEM fine, LEM thick). These alternative representations were used within models of the field experiment and the calculated waveforms were used in an iterative inversion for fracture stiffness. Results show that the EM model and the EDFM model were unsuccessful in matching recorded waveforms. The fine LEM model and the explicit PFM model produced the best results especially after iterative optimisation of the fracture stiffness, giving confidence that further optimisation will lead to improved characterisation of the fracturing from the full waveform data

Luiskan stabiliteetin rakomekaaninen mallintaminen

The stability of slopes are commonly assessed in ways, which exclude the fractures of the rock mass, rather than including them as extending elements. The failures of slopes have been noted to advance through internal flaws and failure zones of the rock mass, such as fractures. By connecting these weakness zones with each other, a surface can be formed, which ultimately acts as a path of failure for the slope. The reason for this study was to research an alternative approach, based on fracture mechanics, to model the stability of slopes. The fracture propagation of a slope was approached by the means of numerical modeling, using a fracture mechanics code, Fracod2D. The software was specifically developed to model the path of fracture propagation, under various thermal-, hydrological-, or time related conditions. With the means to implement hydrological, and thermal coupling to the models, the slope stability could be assessed under the effect of temperatures affected by winter season, and ice ring expansion. As a result of this study, a method for reducing the fracture toughness parameters KIC, and KIIC to represent the properties of rock mass was developed. It was found out, that the effects of temperature change from winter season affect only the surface layer of the rock mass until the depth of 4m, depending on the thermal properties of the host rock. Regarding the fracturing, it was found out that the fractures do not coalesce with each other, unless the distance between the fracture tips is of very small distance, compared to the model geometry. In addition, once the process of fracturing itself has begun to occur, the process is very sensitive towards factors having an effect on the prevailing stress-field, such as water pressure and ice expansion.Luiskan stabiliteetti analyysi suoritetaan useimmiten menetelmin, joissa rakojen kasvun vaikutus kalliomassan lujuuteen jätetään huomioimatta. Kalliomassasta koostuvien luiskien sortumapintojen on huomattu muodostuvan heikkouksista kuten raoista tai rakovyöhykkeistä, jotka yhdistyessään mahdollistavat lopullisen luiskan sortuman. Tämän tutkimuksen tarkoituksena on lähestyä luiskan stabiliteetin mallintamista rakomekaaniselta pohjalta, jolloin luiskan stabiliteetin menetys oletetaan tapahtuvan rakojen kasvusta johtuen. Rakojen kasvun aiheuttamaa stabiliteetin muutosta tutkittiin numeerisesti mallintaen, käyttäen rakojen kasvun mallitamiseen erityisesti suunniteltua ohjelmaa nimeltään Fracod2D. Fracod2D mahdollistaa rakojen kasvun mallintamisen erilaisten hydrologisten, termodynaamisten, sekä aikariippuvaisten kuormitusten alaisena. Näiden ominaisuuksien avulla luiskan stabiliteettia pystyttiin analysoimaan talvesta johtuvan lämpötilan muutoksen, sekä siitä johtuvan jään lajenemisvaikutuksen aiheuttamasta lisätystä kuormasta. Työn tuloksena kehitettiin menetelmä rakomekaanisten lujuusparametrien KIC, ja KIIC madaltamiseksi, mittakaavatekijän kasvaessa laboratorionäytteistä kohti kivimassaa. Talvesta johtuva lämpötilaero sekä jään laajenemispaine vaikuttavat vain kallion pintakerroksissa, noin 4m syvyyteen. Rakojen huomattiin yhdentyvän vain silloin, kun rakojen päät sijaitsevat hyvin lähellä toisiaan. Mallinnuksissa selvisi, että luiskat eivät olleet herkkiä rakomekaanisien lujuusparametrien muutoksille. Kun rakojen kasvua alkaa ilmetä, mallit tulevat erittäin herkiksi jännitystilan muutoksille, kuten jään- tai vedenpaineen aiheuttamaan jännitilan kasvuun

Modified yield-line theory approach to determine spayed concrete flexural capacity

VK: T20703Yield-Line Theory (YLT) is an upper bound method for determining the bending capacity of a thin ductile slab. YLT has been shown to overestimate the flexural capacity of sprayed concrete slabs in some cases (e.g. Uotinen et al. 2013). In this paper, the EFNARC three point bending test on square panel with notch is evaluated using the original YLT, modified YLT and a fracture mechanics approach, and compared to a finite element solution. A small, 20 sample, comparative testing campaign is planned to be carried out in Aalto University in fall 2014. The emphasis is on the cracking capacity of the sprayed concrete, as cracked structures are not accepted and already require renovation. The solutions for each approach are shown and precomputed for the selected C35/45 comparison concrete strength class. The notched slab test was published in 2011 and not many cases are yet available. Comparison of the predictions to two known cases is shown. For future research, we suggest further modifications to the YLT method to represent the structural behaviour more accurately. One approach is to apply the load in steps and calculate the corresponding moment line pattern separately for each load stage. Second approach is to modify the line moment equation to reflect the semi-ductile behaviour, and to accommodate the effect of steel or polymer fibres. The third approach is to incorporate crack growth energy directly into the virtual work equations.Peer reviewe

Wave velocity measurements in three directions on axially loaded water-saturated granite and gneiss core specimens

The density, porosity and mechanical properties from uniaxial compression and Brazilian tests along with measurements of the P- and S-wave velocities in axial and two lateral directions at unloaded state and at increasing axial load were conducted on cylindrical cores of veined gneiss and granitic pegmatoid. The specimens were sampled close to a tunnel wall (0.1– 1.7 m depth) with the aim to find if there is an increasing amount of microcracks due to the excavation in a zone near the surface. Evidence of microcracks was found via the mechanical tests and the wave velocity measurements, due to increased mechanical stiffness and increasing wave velocities at loading. Anisotropy in in the gneiss specimens and also in the granitic pegmatoid was detected and measured via strain and wave velocity measurements. No clear evidence was found of increased amount of microcracks closer to the tunnel wall.Peer reviewe

Thermally Induced Rock Stress Increment And Rock Reinforcement Response

The thermal heating caused by the deposition of spent nuclear fuel containers increases the in situ rock stress during disposal time. The thermal stress increase was modelled using thermo-mechanical modelling. The numerical codes used to establish the effects of heating on the in situ stress field are outlined, together with the rock mass parameters, in situ stress values, radiogenic temperatures and reinforcement structures. This is followed by a study of the temperature and stress evolution during the repository's operational period and the effect of the heating on the reinforcement structures. It is found that, during excavation, the maximum principal stress is concentrated at the transition areas where the excavation profile changes and that, due to the heating from the deposition of spent nuclear fuel, the maximum principal stress rises significantly in the tunnel arch area of NW/SW oriented central tunnels. However, it is predicted that the rock’s crack damage (CD, short term strength) value of 99 MPa will not be exceeded anywhere within the model. An additional study of the radiogenic heating effect on the brittle deformation zones is included. The main conclusion is that, despite deep reaching damage potential in all the load cases studied the currently designed and used reinforcement types and configurations (rock bolts, shotcrete) are capable of handling the dead weight of the damaged rock should this occur, with damage occurring on the shotcrete liner. The long term safety and stability of the repository during its lifetime can be guaranteed by perceiving the reinforcement strategy in two stages. Firstly, by installing the rock reinforcement to sustain the initial stresses and short term increases from the start of deposition with a monitoring programme in place. Secondly, by installing additional reinforcement, if found necessary through monitoring and observation of the underground facilities. In this way, the effect of any time dependent rock stress increase affecting the reinforcement structures can be observed, in addition to creep based damage, thus providing a better level of safety than a single stage design.Peer reviewe