Geosünteetide kasutamise analüüs ja ettepanekud

Abstract

Geosünteedid võivad olla asendamatud abivahendid, täites üliolulisi funktsioone ning pakkudes teedeehitusel ja nende juurde kuuluvate taristuobjektide ehitusel lahendusi, mis parandavad pinnaste ja struktuuride omadusi. Geosünteedid muudavad võimalikuks teede rajamise nõrkadele aluspinnastele, suurendavad tee aluspinnase kandevõimet ja aitavad teiste keeruliste insenerlahenduste puhul, näiteks vähendavad nõlvade erosiooni. Lõputöös olid vaatluse all praegu kättesaadavates juhendites olevad geosünteetide nõuded ja viimase viie aasta jooksul tellitud geosünteetide valdkonna alased arendustööd. Lõputöö analüüsi käigus selgus, et geosünteetide nõuded on laiali erinevates juhendites, mis teeb nende otsimise keeruliseks. Samuti on juhendites olevad geosünteetide nõuded küllaltki pinnapealsed ega aita huvitatud osapooltel teha põhjalikku valikut. Juhenditest puuduvad projekteerimise alused, geosünteetide valiku põhimõtted, geosünteetide hoiustamise ja kvaliteedi kontrolli hindamise juhised. Lõputöös analüüsiti põhjalikult juhendmaterjalide nõudeid ning tehti ettepanekuid juhendmaterjalide täiendamise osas. Ettepanekute osas analüüsiti ja tugineti ka Transpordiameti poolt tellitud kahele arendustööle (geosünteetika kvaliteedikontrolli teadus-arendustöö ja geosünteetide kasutamine teekonstruktsioonis arendustöö), mille põhjal koostati ettepanekud, kuidas oleks võimalik olemasolevaid juhendeid täiendada. Ettepanekud on koostatud põhimõttel, et ka alustav insener suudaks hoomata geosünteetide nõudeid. Ehitussektoris mängib aina rohkem rolli ehitusest õhku paisatav CO2 ekvivalent, millel on suur mõju globaalsele soojenemisele, seetõttu analüüsiti lõuputöös pinnase massivahetuse ja geosünteetidega tugevdamise omavahelist CO2 heitekogust ja ehitusmaksumust. Käesolevas lõputöös kirjeldatud tingimuste arvutuste tulemusel nähtus, et tugevdava geosünteedi kasutamine avaldab keskkonnale potentsiaalselt kuni kuus korda väiksemat mõju kui pinnase massivahetus. Tugevdava geosünteedi kasutamine aitab samuti ehitusmaksumuses kokku hoida, arvutustulemustel selgus, et ehitusmaksumus oli ligi kolm korda soodsam kui pinnase massivahetus. Analüüsi käigus selgus lisaks, et geosünteetide kasutamine vähendab ehituseks kuluvat aega ja aitab säästa kvaliteetse ehitusmaterjali kasutamist, kus kvaliteetse ehitusmaterjali hankimine on loodust kurnav ja majanduslikult kallis. Analysis and Recommendations for the Use of Geosynthetics The main focus of the thesis is to analyse the current requirements for geosynthetics in national guidance materials from the perspective of design, construction, and supervision. Based on the analysis, solutions on how to enhance and update the requirements for geosynthetics guidelines are proposed. The proposals are based on two development research works carried out in Estonia, studies of geosynthetics, and foreign geosynthetics guidance materials. In the first chapter the requirements of the Estonian national guidelines regarding geosynthetics are analysed along with two research and development projects related to geosynthetics. The main issue with the guidelines is their superficiality: leaving unaddressed certain aspects such as the calculation of geosynthetics, the selection of geosynthetics based on their function, and how to assess product compliance and storage on-site. In addition, the requirements for geosynthetics are scattered across several guidelines creating confusion in trying to find specific requirements. The first chapter also analyses two development projects. In the first one, creep behavior tests of geosynthetics were carried out in various chemical environments at temperatures ranging from 10 to 60 degrees Celsius. The study found that geosynthetics made from polyester or aramid are affected by high pH levels (pH levels above 12). The study also focused on the effect of temperature. Since temperatures in Estonia can fluctuate from plus 30 degrees to minus 30 degrees Celsius, a variation of 60 degrees must be taken into account. When using geosynthetics, it is important to select those that can withstand both cold and warm conditions. The most significant temperature fluctuations occur in geosynthetics installed at depths of up to 1 meter. The second development project is based on the use of geosynthetics in road construction. The project addressed the calculation of geosynthetics, the functions of geosynthetics, and aimed to create a unified platform on which all parties interested in geosynthetics could rely. The development project contains some conflict, such as using a soil fine fraction of <0,075 mm. This is an incorrect approach, as in Estonia and Europe in general, standards are used where the fine fraction is <0,063 mm. Additionally, low axle loads have been used 47 in the calculation examples, such as 80 kN, whereas in Estonian conditions the axle load is 100 kN. The second chapter of the thesis provides an overview of the functions of geosynthetics used in infrastructure construction, along with calculations and selection principles. The second chapter also makes suggestions for improvements based on the problems adressed in the first chapter. As the requirements for geosynthetics are scattered across several guidelines, it would be recommended to compile a single and comprehensive geosynthetics guideline that covers the entire field of geosynthetics in infrastructure construction. As environmental protection is becoming increasingly important in infrastructure construction, the third chapter presents the calculation basis for assessing the environmental impact of geosynthetics. Two examples are used in the environmental impact assessment. In the first one geosynthetics are not used and a 4500 m³ soil replacement is carried out, including excavation and backfilling. The calculation takes into account all the steps required for excavation and construction to estimate the CO2 footprint released into the environment. In the second calculation, a section of the same length and width is used, where excavation is not performed, and the base is reinforced with a geosynthetic. The calculation of the environmental footprint of the geosynthetics takes into account the entire life cycle of the geosynthetic product. Calculations comparing the two different solutions show that the use of a reinforcing geosynthetic has an environmental impact six times lower than that of soil mass replacement. The fourth chapter compares the costs of soil replacement and geosynthetic material. Based on the calculations, it is determined that the use of a reinforcing geosynthetic is 2,7 times cheaper than soil mass replacement.