Κατά τον αντισεισμικό σχεδιασμό δύσκαμπτων και ογκωδών κατασκευών εδαφικής αντιστήριξης (π.χ. τοίχοι αντιστήριξης από σκυρόδεμα) οι δράσεις που λαμβάνονται υπόψη κατά τις αναλύσεις ευστάθειας περιλαμβάνουν την στατική και δυναμική εδαφική ώθηση καθώς και την αδρανειακή δύναμη του τοίχου. Οι τρέχουσες μέθοδοι σχεδιασμού (ψευδοστατική, μετακινήσεων) θεωρούν ότι οι δύο ανωτέρω δράσεις ενεργούν συγχρονισμένα, δηλαδή οι μέγιστες τιμές τους ασκούνται ταυτόχρονα στην κατασκευή αντιστήριξης. Εν τούτοις αποτελέσματα πρόσφατων πειραματικών και υπολογιστικών διερευνήσεων υποδεικνύουν ότι (τουλάχιστον στην περίπτωση των ευμετακίνητων κατασκευών αντιστήριξης) αναπτύσσεται σημαντική διαφορά φάσης μεταξύ των δύο δράσεων (ασύγχρονη δράση). Αυτό έχει ως αποτέλεσμα να προκύπτει ιδιαίτερα συντηρητικός σχεδιασμός της κατασκευής αντιστήριξης όταν γίνεται δεκτό ότι τα μέγιστα των δύο δράσεων συμπίπτουν χρονικά (σύγχρονη δράση). Στην παρούσα Διατριβή διερευνάται με παραμετρικές αριθμητικές αναλύσεις η ορθότητα της παραδοχής της σύγχρονης δράσης στην περίπτωση των ακλόνητων κατασκευών εδαφικής αντιστήριξης. Χρησιμοποιείται η μέθοδος των πεπερασμένων στοιχείων (χρήση κώδικα πεπερασμένων στοιχείων PLAXIS) για την προσομοίωση ακλόνητων τοίχων αντιστήριξης από σκυρόδεμα που συγκρατούν μη-συνεκτικό επίχωμα με ελαστοπλαστική σχέση τάσεων-παραμορφώσεων (και κριτήριο αστοχίας Mohr-Coulomb) και υποβάλλονται σε οριζόντια ταλάντωση (είτε αρμονική κίνηση είτε καταγεγραμμένη χρονοϊστορία σεισμικών γεγονότων). Οι παραμετρικές αναλύσεις περιλαμβάνουν τη μεταβολή: α) της σχετικής πυκνότητας του επιχώματος (χαλαρή, μετρίως πυκνή και πυκνή κατάσταση), β) της έντασης της επιβαλλόμενης οριζόντιας ταλάντωσης (0.05g έως 0.7g) και γ) του ύψους του τοίχου (4.0m και 7.5m). Τα αποτελέσματα των αναλύσεων χρησιμοποιούνται κατ’ αρχήν για τον προσδιορισμό της στατικής κατανομής και του μεγέθους των εδαφικών ωθήσεων στον τοίχο. Στη συνέχεια υπολογίζεται, η διαφορά φάσης μεταξύ της αδρανειακής δύναμης του τοίχου και της εδαφικής ώθησης, καθώς και του αντίστοιχου ποσοστού της μέγιστης τιμής της δυναμικής εδαφικής ώθησης που ασκείται κατά τη χρονική στιγμή της μεγιστοποίησης της αδρανειακής δύναμης του τοίχου. Οι αναλύσεις υποδεικνύουν ότι η στατική κατανομή των ωθήσεων είναι τριγωνική με τον συντελεστή πλευρικών ωθήσεων να προκύπτει, περίπου, ίσος με Κ0. Κάτω από συνθήκες δυναμικής φόρτισης το ποσοστό της δυναμικής ώθησης προκύπτει πολύ υψηλό (80% έως 90%) – κυρίως για μετρίως πυκνό και πυκνό εδαφικό επίχωμα – ανεξάρτητα από την ένταση της φόρτισης σε αντίθεση με τις πολύ χαμηλές τιμές (δηλαδή ασύγχρονη δράση) που έχουν προκύψει από αντίστοιχη διερεύνηση για την περίπτωση των ευμετακίνητων τοίχων αντιστήριξης. Ιδιαίτερα ενδιαφέρουσα είναι η παρατήρηση ότι για μικρές τιμές της έντασης της δυναμικής φόρτισης (≤ 0.2g) η συμπεριφορά του υψηλού τοίχου (7.5m) προκύπτει διαφοροποιημένη σε σχέση με αυτή του τοίχου των 4.0m: το ποσοστό της σεισμικής ώθησης είναι πολύ μειωμένο (20% έως 40%), ιδιαίτερα στην περίπτωση των πολύ χαλαρών επιχωμάτων. Παρατηρείται επίσης ικανοποιητική συμφωνία της προκύπτουσας τιμής της εδαφικής ώθησης με αυτή από τη σχέση του Wood(1973) και της αναλυτικής λύσης των Kloukinas et al.(2012). Ιδιαίτερο ενδιαφέρον παρουσιάζει η τροποποιημένη κατανομή των εδαφικών ωθήσεων καθ’ ύψος του τοίχου, οι οποίες προκύπτουν αυξημένες στο ανώτερο τμήμα του. Συμπεραίνεται ότι στην περίπτωση του σχεδιασμού των ακλόνητων τοίχων με μετρίως πυκνό και πυκνό επίχωμα η δράση της δυναμικής εδαφικής ώθησης είναι εύλογο και δικαιολογημένο να θεωρείται σύγχρονη με την αδρανειακή δύναμη του τοίχου. / --

The influence of yielding foundations on the mechanical behaviour of reinforced soil walls including wall deformations and loads (strains) in the reinforcement layers is very complex. Based on a review of the literature, there is a need to quantify and isolate the influence of foundation boundary type and magnitude of foundation stiffness on deformations and reinforcement loads in geosynthetic reinforced soil walls. This thesis presents the results of a series of 1/6-scale reinforced soil wall model tests that were carried out to examine the influence of horizontal and vertical toe compliance and vertical foundation compressibility on wall behaviour. The heavily instrumented walls were constructed in a strongbox that was 1.2 m high by 1.6 m wide and retained soil to a distance of 2.3 m behind the facing. The models were uniformly surcharged in stages following construction. The experimental program consisted of three groups of tests. Group 1 tests involved five walls. One wall was constructed with a very stiff horizontal restraint, and three walls were constructed with different horizontal toe stiffness using combinations of coiled springs. The remaining wall in this series was constructed without any horizontal toe restraint. Group 2 was comprised of three walls. One wall was a control wall with a rigid toe. The other two walls were constructed with different vertical toe stiffness support using different combinations of rubber blocks. Group 3 included a control wall with a rigid foundation and a companion wall constructed with a compressible foam and rubber layers below the backfill soil and the wall facing. The results demonstrate that the quantitative behaviour of the models was affected by the type and magnitude of foundation stiffness. For example, as horizontal toe stiffness increased a greater portion of the total horizontal earth load against the wall facing was carried by the toe. The data showed that the shape of facing lateral deformation profiles changed from rotation about the toe for the case of a very stiff horizontal toe to a more uniform profile for the unrestrained toe case. For the case of a rigid vertical footing support below the facing, vertical toe loads were greater than those computed from facing self-weight alone due to down-drag forces developed at the facing–reinforcement connections as the wall facing moved outward. As vertical toe support stiffness decreased with respect to foundation compressibility below the soil backfill, the magnitude of soil down-drag forces diminished resulting in a decrease in vertical toe load. / Thesis (Master, Civil Engineering) -- Queen's University, 2007-10-27 12:15:56.027

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaves 140-141. / by Chin Pang Wong. / M.S.

No description available.

Experimental and analytic investigations were performed to examine the influences of wall height, backfill behavior, and compaction on the magnitudes of backfill loads on rigid retaining walls. Measurements of lateral and vertical backfill loads were made during tests using the Virginia Tech instrumented retaining wall facility. The tests were performed with two soils, moist Yatesville silty sand and dry Light Castle sand. Two hand-operated compactors, a vibrating plate compactor and a rammer compactor, were used to compact the backfill. The backfill height was 6.5 feet in all of the tests. Analyses of backfill loads were made using a compaction- induced lateral earth pressure theory and a vertical shear force theory. The compaction-induced lateral earth pressure theory was revised from a previous theory. The revisions improved the accuracy with which the theory models the hysteretic stress behavior of the backfill during compaction. The theory was also extended to include the pore pressure response of moist backfill in a rational manner. A vertical shear force theory was also developed during this research. The theory is based on consideration of backfill compressibility and mobilization of interface shear strength at the contact between the backfill and the wall. The theory provides a useful basis for understanding how wall height, backfill compressibility, wall-backfill interface behavior, and compaction-induced lateral pressures affect the vertical shear forces on rigid walls. Studies were also made to investigate the cause of erratic pressure cell readings. An important cause of drift in pressure cell readings was found to be moisture changes in the concrete in which the pressure cells were mounted. It was found that this problem could be mitigated by applying a water-seal treatment to the face of the wall. Both the vibrating plate compactor and the rammer compactor were instrumented to measure dynamic forces and energy transfer during compaction. The force applied by the vibrating plate compactor was about one-quarter of the manufacturer’s rated force. The force applied by the rammer compactor was about twice the manufacturer’s rated force. The transferred energy measurements provided a basis for relating laboratory and field compaction procedures. / Ph. D.

Previous laboratory and field experimental studies of earth pressures exerted on retaining structures and laboratory studies of the at-rest earth pressure coefficient are summarized. The current methods used to evaluate the earth pressures due to compaction are reviewed. The design features of a new instrumented oedometer developed to investigate the effect of number of load cycles on the at-rest earth-pressure coefficient are presented along with the results of a series of tests on Monterey sand #0/30. The Instrumented Retaining Wall Facility developed to provide a means of obtaining experimental measurements of the earth pressures exerted on retaining structures is described. The instrumented wall of the facility is seven feet high and ten feet long and is instrumented to measure horizontal and vertical forces, horizontal earth pressures, horizontal deformations, and temperature. A description of the microcomputer-based data-acquisition system and the software used to record the test results is included. The results of four tests where Yatesville silty sand was compacted in layers in the Instrumented Retaining Wall Facility are presented. The experimental results are compared with the results of similar studies by others and to an analytical method used to estimate compaction-induced earth pressures. / Ph. D.

The safety of gravity earth retaining structures is usually evaluated with regard to: (1) overturning about the toe, (2) sliding along the base and (3) bearing failure of the foundation. Conventional equilibrium methods are utilized in these analyses, which are performed using assumed earth loads based on simplified earth pressure theories. Recent finite element studies performed on gravity retaining walls founded on rock revealed that the use of conventional methods may lead to overly conservative results. The effects of soil-structure interaction result in a greater degree of wall stability than conventional approaches would indicate. This research examines the behavior of gravity earth retaining structures founded on soil. Two methods of analyses were used in these studies : (1) the Following Load method, which does net account for soil-structure interaction effects, and (2) the Backfill Placement method, which does account for soil-structure interaction effects. A procedure called the “Alpha Method” for 2D soil elements was developed for the purpose of improving the post-failure stress-strain behavior of the backfill and foundation soils and incorporated in the finite element program (SOILSTRUCT) utilized in the analyses. A series of analyses demonstrated the effectiveness of the Alpha Method in controlling overshoot and providing good estimates of collapse loads on wall-foundation systems. Following Load analyses indicated that walls on soil become unstable by bearing capacity rather than overturning or sliding. These results also provided the basis for modifications to Vesic’s bearing capacity theory, which extended the applicability of the theory to the conditions encountered in retaining wall problems. The Backfill Placement analyses showed that there are significant differences in behavior between walls founded on rock and walls founded on soil. These analyses also led to new insight into the factors that affect the shear forces within the backfill and which contributes to the stability of the wall. / Ph. D.

The objective of this study was to investigate the accuracy of the procedures employed in the conventional equilibrium method of analysis of gravity-earth-retaining structures founded on rock, using the finite element method of analysis. This study was initiated because a number of existing large retaining structures at various navigation lock sites in the United States that show no signs of instability or substandard performance have been found not to meet the criteria currently used for design of new structures. The results of following load analyses show that when the loss of contact along the base of a wall is modeled in the finite element analysis, the calculated values of effective base contact area and maximum contact pressure are somewhat larger than those calculated using conventional equilibrium analyses. The values of the mobilized base friction angle calculated using both methods are in precise agreement. Comparisons between the results of backfill placement analyses using the finite element method and the conventional equilibrium analyses indicate that conventional analyses are very conservative. The finite element analyses indicate that the backfill exerts downward shear loads on the backs of retaining walls. These shear forces have a very important stabilizing effect on the walls. Expressed in terms of a vertical shear stress coefficient (Kᵥ - r_xy/σᵥ), this shear loading was found to range in value from 0.09 to 0.21, depending on the geometrical features and the values of the material parameters involved in the problem. Another important factor not considered in the conventional equilibrium method is that the displacements of the wall have a significant influence on the distribution of both the stabilizing and destabilizing forces exerted on the wall. In general, as the wall moves away from the backfill, the lateral forces exerted on the wall by the backfill decrease, and the lateral forces exerted on the front of the wall by the toe fill increase. / Ph. D.

Atramines sienas (toliau – AS) veikia įvairios apkrovos dėl kurių susidaro neleistinos deformacijos, atsiranda plyšiai, atraminės sienos pasvyra, siekiant jas apsaugoti nuo tolimesnio svyrimo ir griūties AS būtina stiprinti. Remiantis literatūros apžvalga pastebėta, kad nėra detaliai aptarti žemutinio bjefo (toliau – ŽB) atraminių gelžbetoninių (toliau – g/b) sienų stiprinimo būdai, todėl detalesniems tyrimams pasirinkti 4 hidromazgai (toliau – HTS), kurių atraminėms sienoms reikalingas stiprinimas. Darbo tikslas – įvertinti tinkamiausią gelžbetoninių atraminių sienų stiprinimo išramstant būdą. Siekiant parinkti tinkamiausią išramstymo būdą atlikti palyginamieji ekonominiai bei konstrukciniai skaičiavimai. Pagal ekonominių ir konstrukcinių skaičiavimų rezultatus nustatyta, kad ekonomiškiausias išramstymo būdas – įrengiant monolitines sijas ir „šukas“. / Retaining walls are under the influence of a number of loads, which results in unacceptable deformation, cracks appear and load-bearing walls lean on one side. Retaining walls should be strengthened in order to protect them from further collapse and loping. According to literary review, it is noticed that there is no detailed analysis of the lower pool retaining angled reinforced concrete wall-building techniques. This was the reason why 4 hydroschemes were chosen for more detailed researches in order to determine which retaining walls need strengthening. The aim of this work is to assess the most appropriate angled retaining wall building method. In order to select the most appropriate way of strengthening, comparative economic and structural calculations are done. In accordance with economic and structural results of calculations, it is found that the most economical way of building is a monolithic installation of beams and “combs”.

Žemių užtvankų žemutinio bjefo atraminės sienos (toliau – AS) yra veikiamos nepalankių klimatinių poveikių, vandens, grunto slėgio ir kt. apkrovų. Veikiant agresyvioms aplinkoms ir apkrovoms atsiranda pažaidos, kurios ardo atraminę sieną bei mažina konstrukcijos laikomąją galią. Darbo tikslas – įvertinti nepalankių aplinkos poveikių įtaką atraminių sienų skerspjūvio sumažėjimui. 2007–2010 metais mokslinių ekspedicijų metu įvertinta 21 hidromazgo atraminių sienų būklė. Apžiūrėtos Kauno, Panevėžio, Utenos ir Marijampolės apskričių hidromazgų atraminės sienos, fiksuotos svarbiausios pažaidos. Detaliau ištirta Antanavo hidromazgo atraminė siena, įvertintas sienos skerspjūvio sumažėjimas dėl nepalankių aplinkos poveikių. Pagal tyrimų duomenis pasiūlyti pažaidų, mažinančių atraminių sienų skerspjūvį, remonto būdai. / Retaining walls of lower head–water of ground dams are influenced by negative climatic impacts, water, ground pressure and other loads. Upon the effect of aggressive environment and loads, deteriorations occur destroying the retaining wall as well as reducing the bearing capacity of the constructions. The aim of the work is to evaluate reduction of cross–section of retaining walls as a result of negative environmental impacts. Through the period 2007–2010 on scientific expeditions the condition of retaining walls of 21 hydroshemes was assessed. Retaining walls of hydroschemes in the counties of Kaunas, Panevezys, Utena and Marijampole have been examined, the most significant deteriorations were fixed. Retaining wall in Antanavas hydropower station was examined in detail; reduction of cross–section of retaining wall due to the influence of negative environmental impacts was assessed.