Doğu Karadeniz bölgesi kıyı şeridini korumak için en uygun yapı tipinin belirlenmesi

Abstract

ÖZET Türkiye'nin Doğu Karadeniz Bölgesindeki Kıyı Şeridinde yer alan karayolu, arazinin dar olması nedeniyle sahile çok yakın geçirilmiştir. Zamanla denize müdahale edilmesi nedeniyle kara yolunda ve diğer kıyı bölgesinde tahribatlar oluşmaya başlamış tır. Arazinin çok kıymetli olması yüzünden de koruma yapıları yapılmıştır. Fakat koruma yapıları sadece denize taş doldurmak tan öteye gitmemiştir. Bu çalışmada, koruyucu yapı tiplerinin en uygun olanları belirlenmeye çalışılmıştır. Koruyucu kıyı yapıları, arkaların daki kara parçalarını denizin oyma, aşınma ve taşınma etkilerin den korumak için inşa edilen yapılardır. Kıyı koruma yapıları proje lend iri lirken ortaya çıkan sorunların projeci tarafından iyi etüd edilmesi şarttır. Yanlış projelendirilmiş bir kıyı ko ruma yapısı bitişiğindeki bölgelerin bozulmasına, kendisinin ekonomik ömrünü doldurmadan tahrip olmasına ve büyük bir ekono mik kayba yol açacaktır. Bu tezde, kıyı koruyucu yapı tiplerinin seçimini etkileyen ve bunların projelendirilmesinde temel olan fiziksel, çevresel ve ekonomik faktörler yanında palya (topuk) yüksekliği, yapı önü su derinliği, deniz tabanı eğimi ve dalga yüksekliği gibi parametreler göz önüne alınarak Gömme Topuklu Pere, Topuklu Pere, Tahkimat, Palyalı Tahkimat ve Düşey Duvar önü Tahkimat olmak üzere 5 değişik kıyı koruyucu yapı tipi ortaya konmuştur. Geliştirilen bu yapı tipleri, iki boyutlu model kanalında hareketli ve sabit tabanlı ortamlarda mode llendiri İmi ştir. Teorik çalışmalar, deneysel çalışmalar ile takviye edilmiş ve optimum yapı tipleri sonuç olarak verilmiştir. v

SUMMARY Coastal engineering problems may be classified into four gneleral categories: shoreline stabilization, backshore pro tection (from waves and surge), inlet stabilization, and har- bot protection. A coastal problem may fall into more than one category. Once classified, there are various solutions availab le to the coastal engineer. Some of these are structural; however, other techniques may be employed, such as zoning and land use management. This thesis (DETERMİNİNG THE OPTİMUM STRUCTURE TYPE TO PROTECT SHORELINES OF THE EAST BLACKSEA REGION) deals shoreline stabilization with structural solutions. The structures of shoreline stabilization consists of seawall, bulkhead, revetment, beach nourishment, and groins. Seawalls, bulkheads, and revetments are structures placed pa rallel, or nearly parallel, to the shoreline, to separate a land area from a water area. The primary purpose of a bulkhead is to retain or prevent sliding of the land, with the secondary purpose of affording protection to the upland against damage by wave action. The primary purpose of a seawall or revetment is to protect the land and uppland property from damage by waves, with incidental functions as a retaining wall or bulkhead. There are no precise distinctions between the theree structures, and often the same type of structure in different localities bears a different name. Thus, it is difficilt to say whether a stone or concrete facing designed to protect a vertical scarp is a seawall or a revetment, and often just as difficilt to determine whether a retaining wall subject to wave action should be termed a seawall or bulkhead. All these structures, however, have one feature in common, in that they separate land and water areas. These structures are generally used where it is necessary to maintain the shore in an advanced position relative to that of adjacent shores, where there is a scant supply of littoral material and little or no protective beach, as along an eroding bluff, or where it is desired to maintain a depth of water along the shoreline, as for a wharf. These structures afford protection only to the land immedia tely behind them, and none to adjacent areas up-or dowcoast. When built on a receding shoreline, the recession will continue and may be accelerated on adjacent shores. Any tendency toward loss of beach material in fromt of such a structure may well be intensified. Where it is deisered to maintain a beach in the immediate vicinity of such structures, companion works may be necessary. Factors in designing such a structure: use and overall shape of the structure, location with respect to the shoreline, length, height, and often stability of the soil and ground and water level seaward and landward of the wall. The use of the structure dictitates the selection of the shape. Face profile shapes may be classed roughly as vertical or nearly vertical, sloping, conuex curved, concave curved, vireentrant, or stepped. If unusual functional criteria are m. required, a combination of cross sections may be used. A seawall, bulkhead, or revetment protects only the land and improvements immediately behind it. These structures provide no protection to either upor downcoast areas as do beach fiils. Usually, where erosion may be expected at both ends of a struc ture, wing walls or tie-ins to adjacent land features must be provided to prevent flanking and possible progressive failure of the structure at the ends. Seawalls, bulkheads, and revetment, can be built so high that no water would overtop the crest of the structure, regard less of severity of wave attack and storm-surge levels, though it is sometimes not economically feasible to do so. Seawalls and revetments are usually built to protect a shore from the effects of continuing erosion and to protect shore improvements from damage by mave attack. The distinction between seawalls, bulkheads and revetments is mainly a matter of purpose. Design features are determined at the functional planning stage, and the structure is named to suit its intended purpose. In general, seawalls are the most massive of the three, because they resist the full force of the waves. Bulkheads are next in size; their function is to retain fill, and they are generally not exposed to severe wave action. Revetments are the lightest, because they are designed to pro tect shorelines against erosion by currents or light wave action. A curved-face seawall and a combination stepped and curved-face seawall are built to resist high wave action and reduce scour. Both seawalls have sheet-pile cutoff walls to prevent loss of foundation material by wave scour and leaching from overtopping water or storm drainage beneath the wall. The curved- face seawall also has an armoring of large rocks at the toe to reduce scouring by wave action. The stepped seawall was designed for stability against moderate waves. The tongue groove provides a space between piles that may be grouted to form a sandtight cutoff wall. Instead of grouting this space, a plastic filter cloth can be used to line the landward side of the sheet piling. The filter-cloth liner provides a sand-tight barrier, and eliminates the buildup of hydrostatic pressure which is relieved through the cloth and the joints between the sheet piles. The rubble-mound seawall was built to withstand severe wave action. Although scour of the fronting beach may occur, rock comprising the seawall can readjust and settle without causing structural failure. Structural types of revetments used for coastal protection in exposed and sheltered areas. There are two types of revet ments: the rigid, cast-in-place concrete type and the flexible or articulated armor unit type. A rigid concrete revetment provides excellent bank protection, but the site must be dewa- tered during construction to pour the concrete. A flexible structure also provides excellent bank protection, and can tolerate minor consolidation or settlement witout structural failure. This is true for the riprap revetment and too a lesser extent for the interlocking concrete block revetment. Both the viiarticulated block structure and the riprap structure allow for the relief of hydrostatic uplift pressure generated by wave action. The underlying plastic filter cloth and gravel or a crushed stone filter and bedding layer provide for relief of pressure over the entire foundation are rather than through specially constructed weep holes. Major considerations for selection of a structural type are: foundation conditions, exposure to wave action, availability of materials and costs. Foundation conditions may have a signi ficant influence on the selection of type of structure, and can be considered from two general aspects. First, foundation material must be compatible with the type of structure. A structure that depends on penetration for stability is not suitable for a rock bottom. Random stone or sonme type of flexible structure using a stone mat or plastic filter cloth could be used on a soft bottom, although a cellular steel sheet-pile structure might be used under these conditions. Second, the presence of a seawall, bulk head or revetment may induce bottom scour and cause failure. Thus, a masonry or mass concrete wall must be protected from the effects of settlement due to bottom scour induced by the wall itself. Wave exposure may control the selection of both structural type and details of design geometry. In areas of severe wave action, light structures such as timber crib or light riprap revetment should not be used. Where waves are high, a curved, reentrant face wall or possibly a combination of a stepped-face wall with a recurved upper face might be considered over a stepped-face wall. The factor of availability of materials is related to construction and maintenance costs as well as to structural type. If materials are not available near the construction site, or are in short supply, a particular type of seawall or bulkhead may not be economically feasible. A cost compromise may have to be made or a lesser degree of protection provided. Cost analysis includes the first costs of design and construction and annual costs over the economic life of the structure. Annual costs include interest and amortization on the investment, plus average maintenanc costs. The best structure is one that will provide the desired protection at the lowest annual or total cost. Because of wide variations in first cost and maintenance costs to an annual basis for the estimated economic life of the structure. This thesis deals t 2 developed types of these structure. In this thesis (DEI CRMI CNG THE OPTIMUM STRUCTURE TYPE TO PROJECT SHORELINES OF THE E /ST LACSEA REGION), the experimental studies are realized in two-dim nsional model channel as moving and constant cases. viii