Tekil kazıklara alternatif olarak kullanılan çoklu kazık gruplarının zemin ve malzeme parametresine bağlı olarak seçimi ve maliyet analizi
Single piles and their multi-pile group alternatives selection based on soil and material parameters and cost analysis
- Tez No: 1004234
- Danışmanlar: DR. ÖĞR. ÜYESİ ÜMİT KARADOĞAN
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2026
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Lisansüstü Eğitim Enstitüsü
- Ana Bilim Dalı: İnşaat Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Zemin Mekaniği ve Geoteknik Mühendisliği Bilim Dalı
- Sayfa Sayısı: Belirtilmemiş.
Özet
Bu tez çalışmasında, rekreatif amaçlı kazıklı bir iskelenin temel sistemi için tekil kazık ve çoklu mikro grup kazık alternatifleri, kohezyonsuz zeminlerde düşey taşıma gücü temelli güvenlik şartı altında maliyet odaklı olarak karşılaştırılmıştır. Çalışmanın temel amacı, uygulamada tasarımın erken safhalarında çok sayıda alternatifin hızlı biçimde ön elenmesi ve geriye kalan güvenli seçenekler arasından maliyet açısından rasyonel bir seçim yapılabilmesidir. Senaryo yaklaşımıyla farklı çap, malzeme ve yerleşim düzenlerine sahip kazık alternatifleri tanımlanmıştır. Her senaryo için izin verilebilir düşey taşıma gücü hesaplanarak sabit kabul edilen tasarım talebini sağlayıp sağlamadığı kontrol edilmiştir. Kum zeminlerde kohezyonun ihmal edilebilir olması nedeniyle değerlendirme kazık çevresinde oluşan sürtünme direnci üzerinden yürütülmüştür. Böylece, zemin koşuluna uygun ve izlenebilir bir taşıma gücü hesabı ile maliyet karşılaştırmasına doğrudan temel oluşturan bir güvenlik filtresi oluşturulmuştur. Uygun bulunan senaryolar için maliyet hesabı, mobilizasyon, hazırlık veya imalat ve çakma bileşenleri ayrıştırılarak yapılmış, birim fiyatlar AYGM'nin kıyı ve liman yapıları birim fiyat cetvelinden edinilmiştir. Çelik kazıklar için et kalınlığı 10 mm sabit kabul edilmiştir. Çoklu mikro grup senaryoları için ayrıca normal çakım ve beraber çakım varsayımları ayrı bir duyarlılık çerçevesi olarak incelenmiştir. Beraber çakım, 7 mikro kazığın aynı anda çakılabildiği bir saha organizasyonu kabulünü temsil etmektedir. Bu durumda çakma metrajı eşdeğer çakım adedi üzerinden yeniden ifade edilerek çakma maliyetinin toplam maliyet içindeki payı azaltılabilmektedir. Buna karşılık, mikro grup düzenlerinde eşdeğer kesit alanının artması nedeniyle birim fiyat bandının daha üst aralığa çıkması mümkündür. Sonuçlar, normal çakım varsayımı altında tekil ahşap kazık senaryolarının toplam maliyet açısından avantajlı bir çözüm kümesi sunduğunu göstermiştir. Beraber çakım varsayımının uygulanabilir kabul edildiği durumda ise özellikle ahşap mikro grup senaryolarında çakma maliyetindeki azalma belirginleşmiş ve maliyet sıralamasında önemli değişimler ortaya çıkmıştır. Bu bulgu, kazık düzeni seçiminin yalnızca taşıma gücü denetimi ve geometrik parametrelerle değil, saha organizasyonu ve birim fiyat bandı yönetimi gibi uygulama temelli kararlarla birlikte ele alınması gerektiğini göstermektedir. Çalışmanın kapsamı, kum zeminlerde düşey taşıma gücü temelli bir değerlendirme ile sınırlandırılmış, yatay yükler, dinamik etkiler, kohezyonlu zeminler, oturma performansı ve oyulma etkisinin nicel olarak modellenmesi kapsam dışında tutulmuştur. İleriki çalışmalarda, mikro kazık adedinin azaltıldığı alternatif grup düzenlerinin denenmesi, birim fiyat eşiklerinin tasarım değişkeni olarak sistematik biçimde yönetilmesi ve oyulma ile yatay yük etkilerini içeren performans temelli analizlerle karar destek çerçevesinin genişletilmesi önerilmektedir.
Özet (Çeviri)
Pile foundations are widely used to transfer structural loads to deeper and stronger soil layers when near-surface strata provide insufficient bearing capacity, when settlement control is critical, or when marine structures must be built under demanding ground conditions. In coastal engineering practice, piled systems are common in piers, jetties, and similar waterfront facilities because they offer constructional flexibility and can be arranged to match typical superstructure layouts. Nevertheless, selecting between a single-pile solution and a multi-pile group alternative remains a practical design problem that depends on soil conditions, pile geometry, material type, construction method, and total construction cost. This thesis examines the selection of multi-pile groups as alternatives to single piles through a cost analysis framework that combines a scenario-based evaluation with traceable unit-price calculations. The study does not aim to build a continuous mathematical optimization model. Instead, a finite set of discrete design scenarios is defined, each scenario is checked against the same vertical design demand, infeasible options are eliminated, and the remaining feasible options are compared by total cost. This structure reflects early-stage engineering practice, where designers often need to screen alternatives quickly and transparently before proceeding to project-specific detailed analyses. The engineering setting of the study is a recreational piled pier concept defined under typical dimensional constraints. The comparisons are performed under a constant vertical design demand so that the differences among scenarios can be attributed to pile type, geometry, and installation strategy rather than to changes in loading assumptions. The soil profile is represented by cohesionless soils (sand) with typical relative density states such as loose, medium-dense, and dense conditions. While cohesive soils and lateral load effects are essential for comprehensive marine design, the scenario calculations in this thesis are intentionally limited to vertical capacity in sands to maintain analytical clarity and to ensure consistent comparisons across alternatives. The scenario set includes single-pile configurations and multi-pile group configurations. For group scenarios, seven micro-piles acting together are treated as an alternative to a larger single pile. Scenarios differ in pile diameter, embedded length, number of piles or number of groups, and arrangement-related assumptions as required by the geotechnical framework. The goal is to identify which scenarios satisfy the required allowable vertical resistance and to quantify how the corresponding total costs differ among feasible alternatives. The geotechnical evaluation follows conventional practice by decomposing the ultimate vertical pile capacity into toe resistance and shaft resistance. For cohesionless soils, both components are expressed as functions of effective stress and interface parameters. Allowable capacity is obtained by applying an appropriate safety factor to the ultimate capacity. The same analytical approach is used across all scenarios to ensure that the cost comparison is not influenced by changing calculation methods. Although detailed site investigation data, load testing, and settlement analyses would be expected in final design, the present study focuses on a consistent screening-level framework suitable for scenario comparison. A central element of the thesis is the cost modeling approach based on official unit prices used in Türkiye for coastal and infrastructure works. The total cost is decomposed into three components: mobilization, preparation or ancillary works, and driving or installation. Mobilization is treated as a fixed project-level cost for the scenario comparisons. Preparation quantities are computed according to the relevant measurement rules. Driving cost is calculated by multiplying the applicable unit price by the installation quantity. For steel pipe piles, the wall thickness is fixed at 10 mm throughout the study so that material assumptions remain consistent. In multi-pile group scenarios, the driving unit price is selected according to cross-sectional area ranges. For single piles, the relevant area is the pile cross-section. For micro-groups, the applicable unit price category is determined using an equivalent area defined as the sum of the cross-sectional areas of the seven micro-piles within a group. This choice is consistent with the intent of unit-price classifications that scale installation effort with the installed cross-section. As a result, micro-group scenarios may fall into higher unit price bands than individual micro-piles would suggest. The impact of this mechanism on total cost is explicitly included in the calculations. To reflect construction practice, two installation perspectives are examined for micro-groups. The first is normal driving, where each micro-pile is installed separately and the driving quantity scales with the total driven length of all elements. The second is simultaneous driving, defined in this thesis as the case in which the seven micro-piles in a group can be installed as a single operational unit. Under this assumption, the driving quantity is represented using an equivalent number of driving operations. Mobilization and preparation costs are kept unchanged between the two perspectives so that the cost impact of the installation representation can be evaluated directly. The results indicate that the cost ranking of alternatives is strongly influenced by the driving component and by how installation is represented for micro-groups. Under the normal driving perspective, single-pile solutions, particularly single timber pile arrangements, are generally cost-effective because the total driven length remains limited and the driving cost does not grow excessively. Since mobilization is fixed across scenarios, the primary differentiator becomes the combined magnitude of preparation and driving costs. In this setting, scenarios with moderate installation quantities and favorable unit price categories tend to perform better. For steel micro-group scenarios, normal driving can lead to relatively high total cost because the total driven length increases with the number of micro-piles and driving becomes a major share of the budget. This finding should not be interpreted as a general rejection of steel micro-groups. It shows that, when each micro-pile is treated as a separate installation effort in the cost model, the cumulative driving quantity can outweigh other potential advantages. When the simultaneous driving perspective is applied, total cost can decrease substantially in scenarios where driving dominates the budget. For timber micro-groups, the reduction in the driving quantity can produce a marked decrease in total cost even if the equivalent area places the unit price in a higher band. This outcome emphasizes that installation planning and operational assumptions can change economic conclusions as much as geometric design choices. If site conditions, equipment availability, and construction constraints realistically allow simultaneous installation, micro-group solutions become financially competitive and, in some cases, more economical than single-pile alternatives. From an engineering viewpoint, the selection between a single pile and a pile group should be made with more than vertical capacity checks in mind. In coastal environments, redundancy and load sharing can be valuable under local seabed degradation mechanisms such as scour-related embedment loss at individual elements. In the literature, Yağcı (2017) highlights that group configurations may provide advantageous behavior in such settings. While scour is not modeled quantitatively in this thesis, the cost analysis indicates that multi-pile group solutions do not necessarily introduce a cost penalty when realistic installation perspectives are considered. Under certain conditions, they can also be economically advantageous. The study also identifies a practical cost-control lever for timber micro-groups. Because unit prices for driving are selected by cross-sectional area ranges, small changes in pile diameter or group composition may shift a scenario into a different cost band and cause a discontinuous change in driving unit price. Therefore, managing the equivalent cross-sectional area so that it remains within a favorable band can reduce total cost. In early-stage design, pile diameter selection and group size can be treated as deliberate design variables to control the unit price band while maintaining geotechnical safety. The limitations of the thesis should be stated clearly. The scenario comparisons are limited to vertical bearing capacity checks in cohesionless soils. Lateral loads from waves, currents, wind, berthing and mooring, and seismic actions are not included in the quantitative evaluation. Settlements and serviceability performance are not modeled in detail. Scour is not computed using hydrodynamic or morphodynamic methods; its relevance is acknowledged and discussed qualitatively. Finally, while official unit prices provide a traceable basis, project-specific market conditions and contractor productivity can change absolute costs. The comparative insights remain useful as an early-stage decision aid within the assumptions adopted. Within these boundaries, the thesis provides a structured and transparent framework for comparing pile system alternatives under a fixed vertical design demand. The main conclusions are as follows. Under normal driving, single-pile configurations, particularly timber single piles, tend to be economically favorable within the examined scenario set. Micro-group alternatives can become highly competitive when simultaneous driving is feasible and when unit price band effects are managed through equivalent-area-aware design. Once mobilization is fixed, differences among feasible alternatives are driven primarily by installation-related costs. Installation representation and operational planning therefore have a decisive influence on total cost outcomes. Future work can expand the framework in several directions. Extending the scenario set to cohesive soils would broaden applicability to a wider range of coastal ground conditions. Incorporating lateral pile behavior using p--y curves and soil-structure interaction models would enable performance-based comparisons under combined vertical and horizontal demands. Quantifying scour through empirical relations or coupled hydrodynamic and sediment transport analyses would allow the redundancy advantage of pile groups to be evaluated numerically. Finally, extending the scope from initial construction cost to life-cycle considerations, including durability, corrosion protection, maintenance, and environmental indicators such as embedded carbon, would align the framework with modern sustainability-oriented design practice while preserving the transparency of scenario-based evaluation.
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