Posts: 6,566
Threads: 1,107
Joined: Jul 2011
Seismic Stability of Soil Nail Walls
[attachment=16890]
E-1-Background
Vucetic et al (1997) analyzed the stability of soil nail excavation that were shaken by the
1989 Loma Prieta Earthquake. In brief, the performance of nine different grouted soilnailed
excavations in the San Francisco Bay area during the October 17, 1989 Loma
Prieta earthquake was analyzed on the basis of post-earthquake visual inspections,
subsequent stability analyses and dynamic centrifuge model tests. None of the
excavation showed any signs of movements or significant distress, even though one of
them was located in the vicinity of the earthquake epicenter which experienced strong
shaking and important seismic-related damage to other structures.
E-2-Seismic Soil Nail Stability Evaluation
As implied by the foregoing discussion, a rational procedure to evaluate seismic response
of permanent soil nail walls is by the evaluation of seismic induced deformations just as
is the case for slope stability. The minimum acceptable deformation is judged to be 0.5
percent of the height of the wall or 0.5 inch whichever is larger unless the physical
constraints of the project dictate smaller deformations.
E-3 Discussion
The nine wall configurations as reported by Vucetic et al are summarized on Figure E-4.
The analysis results tabulated in Table 1 for eight of walls shown on Figure E-4 were
plotted and interpolated and extrapolated to compute yield acceleration as a function of
initial computed factor of safety. The results are plotted on Figure E-5. As shown on
Figure E-5, Ky increase with increasing initial static factor of safety in a relatively narrow
range for 7 of the 8 walls.
I want know the cost soil nailing per square feet
Posts: 14,118
Threads: 61
Joined: Oct 2014
Deep excavation is a common part of development to use underground space in densely populated areas. The protection of contiguous building and properties is a major concern of space design. The nailing of the ground is one of these techniques to interchange the conventional retention system for deep excavations. It will also donate significant savings in cost and construction time compared to conventional retention systems. In this study an attempt has been made to make a deep vertical excavation on a terrain of 10 m of height using a wall of ground nail. We also studied the enactment of the soil nail wall under different inclinations of nails to horizontal, ie Ѳ = 0 ° and Ѳ = 15 ° with the water table. The analysis of finite elements of the soil nail wall was carried out to study the behavior of the maximum horizontal displacement of the wall, the maximum horizontal displacement of the nails, the support of the base, the maximum axial force in the nail, The maximum shear force on the nail, Conditions using PLAXIS 2D. The construction process is performed in stages and a global safety factor (FSG) value is maintained above 1.5 to ensure its stability. The length of the nail has a major impact on the behavior of the floor nail wall system; Increased nail length will increase the FSG. The numerical analysis results indicate that the use of the soil nail wall is desirable for imparting stability to the retention systems.
Soil nailing has become a widely accepted method and offers a practical solution for the construction of permanent retaining walls, the stabilization of slopes and the protection of existing cuts against faults. In Malaysia, soil nailing is typically performed on the cutting slope and is installed with the injection as a preventive method due to erosion problem. However, although the effectiveness of the ground-nailing system can be well understood by practitioners, failure of slope and collapse of deep excavation occur continuously, especially for construction in the earthquake zone. Malaysia has numerous earthquake experiences, even this country has been categorized as a low seismicity group. Therefore, it is important in the field of geotechnical engineering to analyze and study the effect of the earthquake to the systems of soil nailing in Malaysia. The objectives of this work are to focus and study this technical question using the finite element program application. This research study selects PGA of 0.08g based on the location of the main population in Malaysia. The safety factor was calculated in this finite element program using the phi-c reduction. The nailing in the ground offers a relatively satisfactory response under seismic, so a pseudo-static method is applied for the study of seismic load. Based on the results of the static analysis, the FOS for deep excavation stabilized with nailing in the soil is 1.54. However, considering the earthquake or seismic load, the FOS is reduced to 1.16 and the percentage reduction is approximately 25%.
The concept of nailing the soil is by inserting steel reinforcement bars or so-called nails to strengthen the soil mass internally. This method is classified as passive inclusions to reinforced soil slopes, excavations or retaining walls. The function of the steel rods introduced into the soil mass is to stabilize the soil mass for deep excavation and this method normally sprayed with the concrete as its lining to prevent erosion. These nails are commonly installed at an inclination of 10 ° to 20 ° horizontally and are tensioned to improve the shear strength of the floor. The nailing of the floor is a topbottom construction. Detailed soil nailing analysis is highly necessary before beginning any nailing installation in the field. One of the methods is the finite element, and recently, the application of finite element advances simultaneously with the development of computer technologies. The finite element analysis is undoubtedly the most suitable to be used to examine the actual deformation characteristics and the failure mechanism of the reinforced structures of the soil.
