Ioannis N. Markou

Democritus University of Thrace | DUTH · Department of Civil Engineering

Hydropower Engineering: Reservoirs - Dams - Specific establishments of hydrodynamic plants - Turbines

The investigation reported herein aims toward the development of novel, easy to-use models based on the pore-size distributions of sands for the injectability prediction of cement suspensions. The models were determined using 367 injectability measurements obtained by conducting injection tests into 54 sands with different gradations. The model per...

The purpose of this research effort is to develop mathematical tools for estimating the strength under undrained loading conditions of various soils reinforced with circular fibers. In this process, a database was created including experimental data from unconsolidated – undrained triaxial compression tests collected from various publications. In...

One method of soil reinforcement is by incorporating fibers, either natural or synthetic. The extent of improvement and the parameters that play a crucial role are the aims of this research effort. Five different soils covering a wide range of AASHTO soil categories were used. Polypropylene fibers of five different types with various lengths and c...

The design of fiber-reinforced soil structures, such as embankments and pavements, can be carried out using the results of unconsolidated, undrained triaxial compression tests conducted on specimens at their “as-compacted” water content and analyzed in terms of total stresses. The effects of soil and fiber type on the mechanical behavior of fiber-r...

Special Issue on ‘Soil-Geosynthetic Interaction’ https://link.springer.com/article/10.1007/s40891-023-00511-5

The investigation reported herein aims toward the development of novel, easy-to-use models based on the pore-size distributions of sands for the groutability prediction of cement suspensions in permeation grouting projects for soil improvement. The models were determined using 367 groutability measurements obtained in this research effort by conduc...

An experimental investigation was conducted in order to evaluate the effectiveness of six new microfine cement grouts obtained by pulverizing three ordinary cements with different chemical composition. Both consolidated-undrained with pore pressure measurement (CU-PP) triaxial compression and hydraulic conductivity tests were conducted on each grou...

Soils reinforced with natural or artificial, randomly oriented fibers are used in various applications such as pavements and embankments. The safe design and construction of projects using fiber-reinforced soils requires the knowledge of their compaction characteristics. Therefore, the present study aims toward (a) the enrichment of the relatively...

Grouting includes a range of processes that involve the injection of wet or dry materials into the ground to provide improved engineering properties. Common aims are to increase strength or stiffness or to reduce permeability within the mass of ground treated. The simplest process in concept is the permeation of the pore spaces with a fluid grout w...

An experimental investigation was conducted to evaluate the influence of factors pertinent to the suspension and the sand on the effectiveness of microfine cement grouts under quick loading conditions, that is, conditions, where the grouted soil mass is loaded at a rate which is much faster than the rate of pore water pressure dissipation and total...

The hydraulic conductivity of 54 sand-sized crushed limestone materials was measured by conducting constant head tests in a rigid-wall permeameter and was estimated using six predictive equations requiring easily obtainable parameters. The gradations tested had effective grain size, D 10 , from 0.079 to 2.15 mm; uniformity coefficient, C u , from 1...

The experimental investigation reported herein aims toward the development of groutability prediction models based on the hydraulic conductivity of sand and other parameters affecting the groutability of cement suspensions. For the purposes of the present study, suspensions of three different cement types, each at four different gradations, having...

Μοντέλα που συσχετίζουν την πιθανότητα επιτυχίας της ένεσης εμποτισμού με τον συντελεστή διαπερατότητας της άμμου και παραμέτρους σχετικές με τα αιωρήματα τσιμέντου, αναπτύχθηκαν με τη μέθοδο της Δυαδικής Λογαριθμικής Παλινδρόμησης. Για την ανάπτυξη και τον έλεγχο αξιοπιστίας τους, χρησιμοποιήθηκαν 366 και 159 πειραματικές μετρήσεις ενεσιμότητας πο...

Ο σκοπός της παρούσας έρευνας είναι η ανάπτυξη μαθηματικών εργαλείων για την εκτίμηση της αντοχής σε ποικιλία εδαφών ενισχυμένων με ίνες κυκλικής διατομής. Σε αυτή την προσπάθεια, δημιουργήθηκε μια βάση δεδομένων με χρήση της διεθνούς βιβλιογραφίας, στην οποία περιλήφθηκαν τα πειραματικά δεδομένα από δοκιμές άμεσης διάτμησης και τριαξονικής φόρτιση...

Στόχος της παρούσας εργασίας είναι η παρουσίαση υπολογιστικών εργαλείων για τον προκαταρκτικό σχεδιασμό του συστήματος βάσης και πρανών Χώρων Υγειονομικής Ταφής Απορριμμάτων (ΧΥΤΑ) με την χρήση γεωσυνθετικών υλικών και η σύγκριση των αποτελεσμάτων τους με στοιχεία από τον σχεδιασμό ενός πραγματικού έργου στην Ελλάδα. Τα εργαλεία που αναπτύχθηκαν, β...

Δοκιμές διαπερατότητας σταθερού φορτίου εκτελέστηκαν σε 54 καθαρές, πυκνές άμμους διαφορετικής κοκκομετρίας και τα αποτελέσματά τους συγκρίθηκαν με τις προβλέψεις έξη γνωστών εξισώσεων. Οι μετρημένες τιμές του συντελεστή διαπερατότητας παρουσιάζουν συνολική διακύμανση σχεδόν ίση με τρεις τάξεις μεγέθους και προβλέπονται ικανοποιητικά από τις εξισώσ...

The design of permeation grouting projects in soil formations is based on the suspension groutability, which is frequently predicted with the utilization of simple groutability criteria. The effectiveness of the groutability estimations made by applying available criteria is documented in the present study. Toward this end, a database was created c...

The shear resistance at soil–geomembrane interfaces is critically important for the proper design of geomembrane-lined side slopes of landfills, reservoirs, and canals. The dependable design and construction of such applications is enhanced by the experimental documentation of the interaction behavior between different soils and various geomembrane...

The purpose of this investigation is the development of mathematical tools for the estimation of the strength values of various soils reinforced with fibers having circular cross-section. In this effort, two databases were created comprising experimental results of direct shear and triaxial compression tests found in different publications. The fir...

The effect of shear box size, geotextile type and properties and sand grain shape and size on the sand – geotextile interaction was investigated experimentally by conducting interface tests with conventional and large-scale direct shear equipment. Four clean uniform sands, one with subangular grains and three with rounded grains of different sizes...

One-dimensional injection tests were conducted on dry and dense sand columns with a height of 36.5 cm for the injectability evaluation of cement grouts. Three ordinary cement types were pulverized to obtain fine-grained cements having nominal maximum grain sizes of 40, 20 and 10 μm. Suspensions of these cements with water to cement (W/C) ratios of...

The effect of shear box size, geotextile type and properties and sand grain shape and size on the sand–geotextile interaction was investigated experimentally by conducting interface tests with conventional (100 mm) and large-scale (300 mm) direct shear boxes. Triaxial compression tests were also conducted on reinforced sand samples in order to eval...

The effect of sand grain shape and size on the mechanical behavior of geotextile-reinforced sands is investigated in the present research, based on the results of triaxial compression tests. Six clean uniform sands differing in grain shape (subangular or rounded grains) and/or grain size as well as one non-woven and three woven geotextiles with or...

state-of-practice) και των πρόσφατων εξελίξεων σε θέματα μελέτης και σχεδιασμού χωμάτινων αντιπλημμυρικών αναχωμάτων, υπό το πρίσμα της γεωτεχνικής μηχανικής. Συγκεκριμένα, παρουσιάζονται τα σημαντικότερα προβλήματα και οι δυνητικοί μηχανισμοί αστοχίας που εμφανίζονται στα χωμάτινα αναχώματα, οι έλεγχοι που πρέπει να πραγματοποιούνται έναντι αυτών,...

Improved mechanical behavior of unpaved roads is encompassed by the use of geotextiles. Geotextiles are manufactured from polymers having high tensile strength and strain capacity relative to the soil. For this reason they cooperate with the soil in strengthening road surfaces, temporary or permanent. They are placed between soil subgrade and stone...

One-dimensional injection tests were conducted on sand columns with a height of 134 cm for the penetrability evaluation of microfine cement grouts. Three ordinary cement types were pulverized to obtain microfine cements having nominal maximum grain sizes of 20 and 10 μm, and these cements were used in the present investigation. Suspensions with wat...

An experimental investigation was conducted in order to evaluate the influence of distance from the injection point and of parameters pertinent to the cement, the suspension and the sand on the effectiveness of microfine cement grouts. Three different cement types, each at three different gradations having nominal maximum grain sizes of 100, 20 and...

Unconsolidated-undrained (single and multi-stage) triaxial compression tests were conducted to evaluate the shear strength of microfine cement grouted sands. Microfine cements of three different types were obtained by pulverising ordinary cements produced in Greece. Multi-stage triaxial compression tests can be used dependably for determination of...

A laboratory investigation was conducted in order to evaluate the effect of sand grain size distribution on the groutability of ordinary and microfine cement suspensions. Four gradations from CEM II/B-M (according to EN 197-1) type of cement were used having nominal maximum grain sizes of 100 μm, 40 μm, 20 μm and 10 μm. Suspensions with water to ce...

Unconsolidated-undrained (single and multi-stage) and consolidated- undrained triaxial compression tests with pore water pressure measurement were conducted to evaluate the deformability and shear strength parameters of microfine cement grouted sands. The effects of cement type and gradation, grout water-to-cement ratio (W/C), test type and distanc...

Three different cements (CEM I, CEM II/B-M and CEM IV/B according to EN 197-1) containing 0%, 23.5% and 38% of pozzolan, respectively, were pulverized to obtain three additional gradations from each cement, with nominal maximum grain sizes of 40, 20 and 10 μm. Cements with the two finer gradations are classified as “microfine” cements. Suspension p...

Geotextile reinforced soil is used in a large number of applications because of its cost and engineering effectiveness. Free draining granular materials, e.g. sands, are specified as backfill material for reinforced soil structures. However, difficulties are encountered when the available quantity of such materials is insufficient. Therefore, the i...

A laboratory investigation was conducted in order to develop a new grout based on pulverized fly ash. Pulverization of a selected Greek fly ash yielded a gradation with D15 = 1.3 μm, D50 = 6 μm, and D85 = 20 μm and Blaine specific surface approximately equal to 8300 cm2/g. Suspensions of this pulverized fly ash, improved with additives, have compar...

A laboratory investigation was conducted in order to develop a new grout based on fly ash produced in Greece. Ptolemaida fly ash was selected because of its hydraulic properties and was pulverized (Blaine specific surface over 8,300 cm(2)/gr, D-15 = 1.3 mum, D-50 = 6 mum, and D-85 = 20 mum) in order to improve its groutability and its hydraulic act...

A Greek lignite fly ash was selected because of its hydraulic properties and was pulverized to produce a specific surface of 8300 cm2/g, and a gradation with D15, D50, and D85 equal to 1.3 m, 6 m and 20 m, respectively. The pulverized fly ash suspension properties were optimized by adding a suitable superplasticizer and a suitable accelerator at op...

Pulverization improves the behavior and the injectability of pulverized fly ash suspensions. The use of additives, a superplasticizer and an accelerator, is necessary. These grouts can be injected successfully into clean sands with gradations bounded by the 16 sieve and yield unconfined compression strength of the grouted sands which is considered...