Jet grout yöntemi ile iyileştirilmiş zeminin bir boyutlu dinamik davranışının sayısal analizlerle incelenmesi
Investigation of one-dimensional dynamic behavior of improved soil using jet grout method with numerical analysis
Yazar: ANIL TORAMAN
Danışman: PROF. DR. RECEP İYİSAN
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Zemin Mekaniği ve Geoteknik Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2021
Konu: İnşaat Mühendisliği = Civil Engineering

Özet:
Deprem yükleri sebebiyle yumuşak-gevşek nitelikteki zemin tabakalarında meydana gelebilecek sıvılaşma ve büyük kayma deformasyonları gibi olumsuzlukların önlenmesi adına zeminin dinamik mühendislik parametrelerini yükselten zemin iyileştirme yöntemlerinin uygulanması günümüzde sıkça tercih edilmektedir. Bu yöntemlerden jet grout yöntemi zemin içinde yüksek modüllü kolon oluşturarak zemin profilinin kayma rijitliğini arttırması sebebiyle Geoteknik deprem mühendisliği problemlerinde tercih sebebi olmaktadır.
Bu çalışmada Sakarya ili, Adapazarı ilçesinde yer alan bir sahada farklı boy ve yerleşimde (alan değiştirme oranı) jet grout uygulaması yapılma senaryoları modellenerek kuvvetli yer hareketi sırasında zemin tabakalarında meydana gelebilecek değişimler bir boyutlu - doğrusal olmayan yer tepki analizleriyle parametrik olarak incelenmiş ve elde edilen sonuçlar tartışılmıştır. Araştırma kapsamında taban kayası derinliğinin ve alt tabaka kalınlığının etkisinin belirlenebilmesi için parametrik zemin profilleri oluşturulmuştur. Yer tepki analizlerinde kullanılan deprem kayıtları 2019 yılında yürürlüğe giren Türkiye Bina Deprem Yönetmeliğinde (TBDY) belirtilen hususlara göre ölçeklendirilmiştir. Analizler sonucunda hem jet grout kolonlarının boyunun ve alan değiştirme oranının hem de taban kayası derinlikleri ve alt tabaka kalınlıklarının analiz sonuçlarına etkisi irdelenmiştir. Elde edilen sonuçlar mühendislik bakış açısı ile değerlendirilerek yorumlanmıştır.

Abstract:
Earthquake waves are occurred by breaking in faults and continue most of their journey through rock layers until they reach the ground surface. When they come to areas close to the surface, they pass through the ground layers and reach the ground surface. Earthquake waves advancing in the ground layers both cause changes in the structure of the ground layers that they pass through and are exposed to some changes in their own wave structure. While the changes in the soil layers are the deformations that occur depending on the shear stiffness (G) and damping ratio (D) of the soil layers, the changes in the wave structure are the amplification or deamplification in the wave amplitudes called soil amplification. One of the most important tasks of civil engineers is to design earthquake resistant structures. For this reason, it is a frequently preferred method to perform site-specific ground response analyzes where the behavior of the ground surface and soil profile at the time of earthquake can be modeled. Ground response analysis can be performed with a total of three different solution methods: linear or equivalent linear method in the frequency domain and non-linear method in the time domain. Ground response analyzes can also be performed in one, two or three dimensions depending on the field topography. Since one-dimensional analyzes are more practical than others, they are frequently preferred especially in areas with horizontal sublayers. With ground response analysis, design spectra and soil amplifications can be obtained on the ground surface, while displacements and shear strains along the soil profile can also be calculated. In order to prevent negative effects such as liquefaction and large shear deformations that may occur in soft-loose soil layers during an earthquake, it is frequently preferred to apply soil improvement methods that increase the dynamic engineering parameters of the soil. Among these methods, jet grout method is preferred in Geotechnical earthquake engineering problems because it increases the shear stiffness of the soil profile by creating a high modulus column in the soil.
In this study, the changes that may occur in the soil layers during strong ground motion using the jet grout application performed with different length and area displacement ratios in a field located in Adapazarı district of Sakarya province were parametrically examined with one-dimensional - nonlinear ground response analysis and the results were discussed.Within the scope of the research, parametric soil profiles were created to determine the effect of bedrock depth and model sublayer thickness. Earthquake records used in ground response analyzes have been scaled according to the issues specified in the Turkish Building Earthquake Regulation (TBDY), which came into force in 2019. As a result of the analyzes, the effects of both the length of the jet grout columns and the area displacement ratio, as well as the bedrock depths and substrate thicknesses on the analysis results were examined.
Three drilling works were carried out in the field which is the subject of this study. In the drillings, it was observed that the soil profile is generally composed of medium plasticity clays, but there is a sand band between 12 and 15 m. However, this layer, which would cause confusion in the analysis results, was not taken into account within the scope of one-dimensional ground response analysis and all layers were determined as clay layers. In SPT tests performed during drilling operations, the number of blows generally varies between 6 and 25 and tends to increase with depth. The plasticity index of the clay soil layers defined in all analysis sets was accepted as 20. The reason for this is that the plasticity index can seriously affect the behavior of soil layers under dynamic loading conditions and the effect of the plasticity index will not be examined in this study. In addition, in models with shallow bedrock depth, the bedrock layer was defined as elastic rock and the shear wave velocity of the bedrock was accepted as Vs=760 m/s while the unit volume weight was 22 kN/m3. There is no SPT-N blow data after the first 30m depth in the relevant field. In models with shallow bedrock layer, it is necessary to determine the engineering parameters of the soil layers up to the bedrock layer after the first 30m depth. Since the bedrock layer shear wave velocity is assumed to be 760 m/s in the rock layer shallow models, it is predicted that the shear wave velocity along the profile increases equally in the subsoil layers after 30m depth. In addition, in the models, the unit volume weight of the soil layers is assumed to be 18 kN/m3 at the first 10m depth, 19 kN/m3 between 10m depth and 20m depth, and 20 kN/m3 afterwards. In models with ground improvement with jet grout, the shear wave velocities of the improvement depth were changed to increase with the jet grout area replacement rate. Thus, by increasing the shear wave velocities at the improvement depths in the models, the improvement effect can be examined with one-dimensional ground response analysis.
In order to use in one-dimensional ground response analysis, a total of 44 earthquake records, 2 of which were horizontal, of 22 separate earthquake records selected for models with deep bedrock and shallow bedrock, were scaled using the simple scaling method. The scaling process was scaled so that the average of 2 separate horizontal directions (H1 and H2) of 11 earthquake records selected from the station with Vs>760 m/s shear wave velocity selected for models with shallow bedrock resembles the design spectrum with ZB local design class. The average of 2 different directions of 11 earthquake records selected from the station with 180 m/s