International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 11 Issue: 03 | Mar 2024
p-ISSN: 2395-0072
www.irjet.net
BEHAVIOR OF DOUBLE ROW MICROPILE WITH GROUTED NAIL SYSTEM IN DEEP EXCAVATION Archana R1, L Govindaraju2 1Post graduate student, Dept. of civil engineering, UVCE Bangalore University, Bengaluru 2Professor, Dept. of Civil Engineering, UVCE Bangalore University, Bengaluru-560056
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Abstract - Deep excavation is a common practice of construction in densely populated areas, uncertainty problems can arise due to the significant settlement at the ground surface and large movements at the facing of the excavation walls. Stabilizing these excavations can be achieved by the most popular methods such as micropile and nailing system. This method has also been widely used to stabilize natural slopes and earth retaining structures. In the present study, numerical modelling and the analysis of an 8m deep excavation supported with different earth retaining systems has been carried out by adopting finite element-based software PLAXIS 2D. A parametric study is conducted using a double row micropile system and a composite system using micropile and nail system. The behavior of the soil body, the forces generated in the micropile, nails, and global safety factors are compared for each case in both static and dynamic conditions. In the case of a double row micropile, the soil body collapse during the final excavation indicating instability condition. To overcome this problem, a composite system has been adopted. The influence of building load on the stability of deep excavation has also been investigated in the present study. The building is placed at different offsets from the excavation line and the behavior of the soil body is compared for all the cases. It is found that when the building is at the edge of the excavation line without any offset, the maximum displacement and bending moment are observed and vice versa.
area, some flexibility in basement layout and design allow techniques such as soil nail and micropile to be employed even for deep excavation with basement of greater depth. Now a days in Earth retention or Deep excavations stabilization are generally followed by many methods here we followed Micropile and Soil nailing technique. In this present study a Composite system using double row micropile with and without nailing system is analysed for a deep excavation of 8m using finite element package PLAXIS 2D. The system consist of the Double row micropile with grouted nailing technique is adopted in the way such that the system retains the soil and prevent the soil from cave-in or collapse.
1.1 Micropile A micropile is a small-diameter (typically less than 300 mm), drilled and grouted replacement pile that is typically reinforced. Generally, micropiles are applicable when there are problems with using conventional deep foundation systems. These problem conditions include: obstructions, adjacent structures, limited access job sites, and other shaky areas like caves, sinkholes, underground rivers. For example, micropiles are commonly the preferred foundation choice in the challenging areas that feature nearby buildings and difficult access [3]. Installation techniques vary depending on the load bearing specifications of the project. The selection of the installation technique depends largely on soil conditions and load transfer requirements. Generally, micropile consists of two general applications, a) Structural support b) In-situ reinforcement
Key Words: Deep excavation, Composite system, Double row micropile, Grouted nail, PLAXIS 2D
1.INTRODUCTION Due to rapid urban developments and growing population in the major cities around the world, the need for underground space has increased. Therefore, deep excavations for development of underground space, such as subway transportation networks, tall buildings basements, underground car parks, and shopping centres have been widely used [2]. However, due to scarcity of land, major developments are increasingly being carried out in peripheral areas of the city. This situation presented unique challenges and opportunities for innovative design as the selling price is not enough for conventional basement excavation technique (e.g. Diaphragm wall) to be economically feasible. However, with larger development
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1.2 Soil nailing Soil nail walls are particularly well suited to excavation applications for ground conditions that require vertical or near-vertical cuts. They have been used successfully in highway cuts; end slope removal under existing bridge abutments during underpass widening; for the repair, stabilization, and reconstruction of existing retaining structures; and tunnel portals [13]. Soil nailing is an economical technique used to stabilize existing slopes and to construct retaining walls from top down. The soil reinforcement process uses steel tendons which are drilled
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