Priprava tal za temeljenje na barju : magistrsko delo št.: 271/II. GR

Dragan, Lea (author), Pulko, Boštjan (mentor), Smolar, Jasna (comentor)

Ljubljansko barje na površju gradijo sloji zelo mehkih jezerskih sedimentov, meljev in glin, pod njimi so pretežno prodni aluvialni sedimenti do predkvartarne skalne podlage, ki se lahko nahaja tudi globlje od 150 m. V slovenskem prostoru je barje iz geološkega in geotehničnega vidika posebnost, naravna znamenitost in v gradbeno tehničnem smislu velik izziv. V magistrski nalogi smo zato analizirali in primerjali učinke različnih ukrepov priprave (izboljšanja) barjanskih tal za temeljenje stanovanjskih objektov. V začetnem delu naloge smo opisali naravne značilnosti območja, s poudarkom na geološki sestavi tal in geotehničnih pogojih. Pregledali smo literaturo o preteklih izkušnjah z gradnjo območju Ljubljanskega barja. V nadaljevanju so teoretično predstavljeni možni ukrepi izboljšanja temeljnih tal. Opisali smo vertikalne drenaže in gruščnate kole. Obravnavali smo terenske preiskave (CPTu), ki so bile izvedene na eni od lokacij predvidene gradnje z značilno sestavo barjanskih tal. Izvedli smo laboratorijske preiskave: ugotavljanje vlažnosti, ugotavljanje gostote zrn, edometrski preskus s postopnim obremenjevanjem, preskus s konusom, ugotavljanje koeficienta vodoprepustnosti ter ugotavljanje meje židkosti in plastičnosti. Rezultate terenskih in laboratorijskih preiskav smo primerjali in oblikovali model tal, ki je bil podlaga za geotehnične analize. Izvedli smo računske analize več variant priprave tal (predobtežba, gruščnati koli, vertikalne drenaže) in za vsako uporabili tri različne analize: dve teoretični (s konstantnim modulom stisljivosti po slojih in s spremenljivim modulom stisljivosti po globini in slojih) ter numerično s pomočjo programskega orodja Plaxis. Opisali smo še model z upoštevanjem lezenja. Rezultate računskih analiz smo primerjali in podali predlog priprave tal pred gradnjo stanovanjskih objektov.

• Language: Slovenian
• Keywords: gradbeništvo, magistrska dela, GR, Barje, posedki, Soft Soil, Plaxis, CPTu, laboratoriji, vertikalne drenaže, gruščnati koli
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Place of publishing: Ljubljana
• Publisher: [L. Dragan]
• Year: 2023
• Number of pages: XVI, 44 str., 13 str. pril.
• PID: 20.500.12556/RUL-145629-0da13782-b2c6-d259-c64e-efb0d617c9f3
• UDC: 624.131.38(497.4)(043.3)
• COBISS.SI-ID: 151835395
• Publication date in RUL: 27.04.2023

Secondary language

• Language: English
• Title: Preparation of soft foundation ground at the Ljubljana Marsh for the construction of residential buildings : master thesis no.: 271/II. GR

Abstract

At the Ljubljana Marsh, the top soil layer consists of very soft lacustrine sediments (silt and clays), and covers the layer of mostly gravelly alluvial sediments lying on the pre-Quaternary rock base. Its depth varies and can reach over 150 m. From the geological and geotechnical point of view, the Ljubljana Marsh is a unique natural landmark in Slovenia and presents a great challenge in terms of planning and design of built environment. In the thesis, we analyzed and compared the effects of different ground improvement methods for the foundation of residential buildings on soft lacustrine sediments. In the first part of the thesis, we described the area of Ljubljana Marsh, with an emphasis on the geological and geotechnical conditions. Next, overview of scientific literature about past experience with the foundation and construction on the soft lacustrine sediments is presented. Two ground improvement techniques (wick drains and stone columns), which were used in numerical analysis, are also described. The second part deals with existing geotechnical data, obtained from field testing and analyzes newly acquired data of laboratory investigations carried out as part of this thesis (determination of water content, determination of particle density, oedometer test, fall cone test, determination of liquid and plastic limits). The results of field and laboratory investigations were compared and a typical marshland soil profile for further numerical analysis was designed. In the last (third) part of the thesis, numerical analysis was carried out for three types of ground improvement methods: preloading, wick drains and stone columns. Efficiency of each ground improvement techniques was analyzed in three different ways: two analytical (first with constant soil stiffness and second with variable soil stiffness) and one numerical procedure (software Plaxis). Since the soft lacustrine sediments exhibited significant secondary consolidation in oedometer, also secondary consolidation settlements were calculated using soft soil creep model (Plaxis). Based on the comparison of results of numerical analysis, advantages and disadvantages of the ground improvement techniques at the Ljubljana Marsh for the construction of residential buildings are highlighted.

• Keywords: civil engineering, master thesis, Marsh, settlements, Soft Soil, Plaxis, CPTu, laboratories, wick drains, gravel columns