ANALISIS STABILITAS BACK-TO-BACK MECHANICALLY STABILIZED EARTH WALLS (STUDI KASUS JALAN LAYANG DI SULAWESI SELATAN)

In urban areas, the requirement for roads is always increasing. This has resulted in various problems such as limited land so that it needs to construct a proper retaining wall. The type of retaining wall that will be discussed is back-to-back mechanically stabilized earth walls. The author analyzes the minimum reinforcement length required for the stability of the retaining wall structure. The author also analyzes the use of backfill material from back-to-back mechanically stabilized earth walls. In this study, two types of backfill materials were used, sand and laterite. The author analyzes the stability of the structure using manual calculations and with software based on finite element methods with several differences in the reinforcement length of the geogrid. In manual analysis obtained the tensile force that occurs in the geogrid and the safety factor for the external stability. In the analysis using the software obtained the safety factor and deformation that occurs in the structure. The results of this study are the minimum ratio of reinforcement length to height, that is L = 0.66H for sand and L = 0.6H for laterite. The requirement of geogrid tensile capacity for laterite is smaller than for sand.Keywords: reinforcement length, mechanically stabilized earth walls, geogrid, safety factorPada daerah perkotaan, kebutuhan akan jalan selalu meningkat. Hal ini mengakibatkan berbagai masalah seperti keterbatasan lahan sehingga perlu konstruksi dinding penahan tanah yang tepat. Jenis dinding penahan tanah yang akan dibahas adalah back-to-back mechanically stabilized earth walls. Penulis menganalisis panjang penjangkaran minimum yang diperlukan untuk statbilitas struktur dinding penahan tanah. Penulis juga menganalisis penggunaan material timbunan dari back-to-back mechanically stabilized earth walls. Pada penelitian ini digunakan dua jenis material timbunan yaitu pasir dan tanah merah. Penulis menganalis kestabilan dari struktur menggunakan perhitungan manual dan dengan software berbasis metode elemen hingga dengan beberapa variasi panjang penjangkaran dari geogrid. Pada analisis manual, diperoleh gaya tarik yang terjadi pada geogrid dan faktor keamanan dari stabilitas eksternal struktur. Pada analisis menggunakan program diperoleh faktor keamanan dan deformasi yang terjadi pada struktur. Adapun hasil dari penelitian ini yaitu rasio panjang penjangkaran terhadap tinggi minimum yaitu L = 0,66H pada pasir dan L = 0,6H untuk tanah merah. Kebutuhan kapasitas tarik geogrid untuk tanah merah lebih kecil daripada pasir.Kata kunci: panjang penjangkaran, mechanically stabilized earh walls, geogrid, faktor keamanan

Geotechnical lessons from the Mw 7.1 2018 Anchorage Alaska earthquake

The 2018 Mw 7.1 Anchorage, Alaska, earthquake is one of the largest earthquakes to strike near a major US city since the 1994 Northridge earthquake. The significance of this event motivated reconnaissance efforts to thoroughly document damage to the built environment. This article presents the spatial variability of ground motion intensity and its correlation with subsurface conditions in Anchorage, the identification of liquefaction triggering in the absence of surficial manifestations (such as sand boils or sediment ejecta), cyclic softening failure in organic soils, and the poor performance of anthropogenic fills subjected to cyclic loading. In addition to lessons from observed ground deformation and geotechnical effects on structures, this article provides case studies documenting the satisfactory behavior of improved ground subjected to cyclic loading and the appropriateness of current design procedures for the estimation of seismically induced sliding displacements of mechanically stabilized earth walls.

Numerical Study of the Behavior of Back-to-Back Mechanically Stabilized Earth Walls

Back-to-back mechanically stabilized earth (MSE) walls can sustain significant loadings and deformations due to the interaction mechanisms which occur between the backfill material and reinforcement elements. These walls are commonly used in embankments approaching bridges, ramps, and railways. The performance of a reinforced wall depends on numerous factors, including those defining the soil, the reinforcement, and the soil/reinforcement interaction behavior. The focus of this study is to investigate the behavior of back-to-back mechanically stabilized earth walls considering synthetic and metallic strips. A two-dimensional finite difference numerical modeling is considered. The role of the soil friction angle, the distance of the reinforcement elements, the walls’ width to height ratio, and the quality of the soil material are investigated in a parametric study. Their effects on the critical failure surface, shear displacements, wall displacements, and tensile forces on the reinforcements are presented. The interaction between back-to-back reinforced walls strongly depends on the distance between walls and modifies the critical failure surface location.