Self Drilling Soil Nailing Method
- Hollow bars are used in self driven soil nailing method.
- Bars are drilled into the slope surface. Grout injected simultaneously during the drilling process.
- It is faster than drilled grouted nailing.
- Lastly, self-drilling soil nailing method provides more corrosion resistance to nails than driven nails.
Fig.8:Self driven soil nail method
Soil Nailing For Slope Stabilization
INTRODUCTION
Slope failure downward movement of soil ØShear stresses > Shear strength ØShear strength is the function of cohesion & internal friction >
Slope stability represented in terms of factor of safety ØSafety factor = Resisting force / Driving force ØIf FOS > 1, then safe or stable slope Ø If FOS < 1, then unsafe or unstable slope
LEM Based on static equation of forces Ø Soil mass above the slip surface is divided into slices Ø Shear & normal inter slice forces are determined v
FEM Based on the concept of stress strain relationship ØStructure is divided into smaller elements called finite elements ØProperties of these elements are formulated & combined to obtain solution for the entire structure
ÒSlope stability analysis using LEM & FEM methods
SCOPE
Soil nailing provides: ÒHigh durability, reduced maintenance cost and highly resistant against environmental influences ÒImproved infrastructure in terms of speed & ease of construction, economy, aesthetics etc. ÒIncreased interaction with soil ÒControl erosion and landslides
OBJECTIVES
ÒSlope stability analysis using Swedish Circle Method ÒFEM model study using PLAXIS 2D ÒVerification of effect of nail length, nail inclination, nail configuration and spacing of nails
STABILITY ANALYSIS SWEDISH CIRCLE METHOD
Procedure v\
Draw the slip surface vTo locate the most critical circle, Fellenius line AB
is drawn vTo draw Fellinius line AB, B is located at a depth H and at a
SCOPE FOR FUTURE WORK
Numerical Analysis Of The Effects Of Soil Nail On Slope Stability
@article, author=, journal=, year=, volume=, pages=}
- Computer Science
- International Journal of Computer Applications
- Journal of Physics: Conference Series
- Engineering, Technology & Applied Science Research
- Mathematics, Physics
- IOP Conference Series: Earth and Environmental Science
- View 2 excerpts, cites background
- International Journal of Geo-Engineering
- View 1 excerpt, cites methods
- Environmental Science
- View 1 excerpt, cites background
- View 1 excerpt, references methods
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What If The New Slope Has Poor Subsoils
While there is often good control over the materials and methods used to construct a new slope, the existing subsoils may be a problem that could create instability. If these pre-existing soils exhibit low shear strength and/or high compressibility, this could create slope stability issues for the newly constructed slope regardless of the care taken during slope construction. Methods to improve slope or embankment subsoils include Ground Improvement, and Rigid Inclusion approaches. The Geopier Ground Improvement Methods have been very successful in stabilizing subsoils for new slopes, embankments, or retaining walls.
How Is Slope Stability Achieved For New Slope Construction
New slope construction provides the design team with the advantage of conducting detailed engineering of the proposed slope and the availability of multiple approaches, depending on the specifics of the planned slope. Many factors are involved in the design of new slopes/embankments. They include the height of slope, slope inclination, right of way or available land, materials used in construction, existing and future groundwater and surface water conditions, and existing subsurface soils.
Slope stability for new slopes is achieved through various methods, depending on the nature of the grade separation, embankment dimensions, and shape, as well as other factors. Typical methods for building new slopes from steep-sloped to vertical faces include Mechanically Stabilized Earth walls , Reinforced Soil Slopes with wire mesh-faced systems , and often include a geogrid or steel-strip tieback system. Other approaches for near-vertical walls or step-back systems include cast-in-place retaining structures, gabion baskets, and stacked natural or cultured stone/block systems.
If the proposed new slope is a cut-slope and there is not enough accessible land for a slope that is stable naturally , the Geopier SRT system can be applied to steepen the cut slope to as much as 1H:1V very cost-effectively. This can provide more useable land above or below the slope and allow the slope to fit within Right of Way constraints.
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Launched Soil Nail Support Type In Slide2
The creation and inclusion of the Launch Soil Nail support type in Slide2 culminates a years-long collaboration between Rocscience and GeoStabilization. The Launched Soil Nail support type in Slide2 allows the user to input the structural properties of the outer tube and inner reinforcing bar. It also allows the engineer to specify the resistance type the support provides – tensile, shear, or a combination of the two. Slide2 2018 uses the theory outlined in the USFS/FHWA manual to calculate the ultimate shear resistance, performing the calculations within the program code, thereby streamlining the analysis and reducing the opportunity for transposition errors between separate programs.
We are excited that these updates to Slide2 allow designers to add this important tool to their geohazard mitigation toolbox, states Roch Player, PE, GeoStabilizations Chief Engineer. He continues, by providing more options to the profession, the better we all can serve the public and protect them from the dangers of geohazards.
Slope Stability And Soil Nailing
DeepEX performs slope stability analyses according to several methods , so that user do not have to export data to another package! DeepEX can also design soil nail walls as it incorporates the recommendations by the French Clouterre, AASHTO LRFD, and Eurocodes.
No Additional Cost: The Slope Stability Analysis module is available in all DeepEX versions! Review All Versions
Using this method, and working from the top downward, a mass of reinforced soil is gradually built up. In order to keep the soil from caving in between the bars, some sort of facing needs to be installed. This facing is generally constructed with some shotcrete reinforced by a welded wire mesh. This facing can be vertical, battered to a wide variety of angles, or made up of a series of benches. The passive bars are often referred as nails and the soil reinforcing technique is known as soil nailing.
Once constructed, a soil nailed wall shows a certain similarity with a Reinforced Earth wall. However, the fact that a soil nailed wall is been built downward with the soil being reinforced in situ, while a Reinforced Earth wall is constructed by building an embankment that is then strengthened as the work progresses, constitutes an essential difference between the two.
DeepEX can also design soil nail walls as it incorporates the recommendations by the French Clouterre, AASHTO LRFD, and Eurocode.
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Soil Nails For Slope Stability
Retaining and protection of foundation excavation is supporting, reinforcing and protecting method to guarantee safety of the underground structure and surrounding environment.
As a structural system, retaining and protecting of foundation excavation should meet the demand of stability and deformation, thats also the ultimate limit state and servicing limit state.
The ultimate limit state refers to larger-scale instability when supporting structure is damaged, toppled, slid and collapse. While servicing limit state refers to that soil bodies deformation influences normal use, but it doesnt create instability.
So supporting design should have enough safety factors to avoid instability and then control displacement.
As for rigid supporting structures, like soil retaining pile, continuous wall support system, their displacement is small and should be controlled in 30mm As for soil nails for slope stability in good geological conditions, advance support and pre-stressed bolt are adopted to control to smaller displacement and it will be greater than 30mm.
Advantages Of Soil Nails
- Versatile: Easily adjusted for subsurface conditions due to various installation methods and design redundancy
- Constructed in a wide variety of soil and rock conditions
- Easy to install along irregular surfaces
- Ideal for tight/difficult access, high/low reach, low overhead conditions, and lateral obstructions
- Minimal noise and vibrations are generated during construction
- Can be designed for limited space compared to gravity, cantilevered, or anchored wall systems
- Can be used as a backform for new structures/foundations
- Shotcrete facing, used in conjunction with soil nails, can be sculpted to provide a decorative permanent retaining wall
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Soil Nails For Temporary Shoring Applications
Excavation is a critical part of many construction projects. Whether you are building a new roadway, hospital, school, or mixed-use development, it is often necessary to perform significant cuts of soil in order to facilitate the overall construction of the project. In many cases, it is costly or impractical to lay back the excavation at a safe angle based on the soil type. If this is the case, utilizing soil nails and for provides a safe and economical advantage when compared to other systems such as soldier pile/lagging and secant pile walls in the right soil conditions.
Slope Stabilization & Soil Nails
Soil nailing is an efficient, effective and economical method of soil reinforcement. The reinforcement is installed into the slope face of in-situ ground, whether natural soil or an existing fill, stabilizing such material. Soil nailing can be used to stabilize, existing structures such as unstable slopes, embankments and retaining walls. The use of soil nails can be adopted for the stabilization of cuttings and coastal and quarried cliffs. The construction of new steep slopes for widening of infrastructure routes, new developments and new retaining walls, has seen an increase in the use of soil nailing.
This method of soil reinforcement can be used for both permanent and temporary applications and has been used by all the main UK infrastructure owners.
The Ischebeck TITAN soil nail is a self-drilling, case-less installation using the cement grout to stabilize the drill hole, during the installation. The TITAN system is therefore installed at a much faster production rate than that of a drilled and cased technique which is required for a solid bar soil nail.
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How Oasys Proved Invaluable
AnalysisA parametric study was carried out by varying the nail parameters, including nail inclination, nail length etc. and slope geometry.To perform the stability analysis, basic input parameters required for Oasys Slope were: Failure criteria Material strength parameters including soil, nail and facing Factor of safety for materials Position of phreatic surfaces Selection of approximate centre and radius of the slope circleIn the study, the Mohr-Coulomb failure criteria was selected for the stability analysis i.e. circular failure surfaces were selected. The input soil properties are unit weight of the soil, both in saturated and unsaturated conditions, cohesion and internal angle of friction of the soil. Slope stability analysis was performed with and without phreatic surface. For selection of the slip circle, it was assumed the slip circle should pass through the toe of the slope and no portion of slip circle should pass through the base layer of the slope.Influence of nail layout on the FOS of soil-nailed slope
Influence of facing thickness on the factor of safety of soil-nailed slopes
Variation of FOD with and without phreatic surface
Link to paper:
Launched Soil Nail Method
- In this method of soil nailing, the steel bars are forced into the soil with a single shot using compressed air mechanism.
- The installation of soil nails is fast, but controls over length of bar penetrating the ground is difficult.
- Utilized to reinforce an unstable or potentially unstable soil mass. capacity into the sliding soil.
- Finally, nail diameter is 38mm and its length is around 6m.
Fig.10:Launched soil nail method
- Stabilization of existing retaining wall
- Excavating retaining structures in urban areas for high rise buildings and underground facilities.
- Landslide redemption
- Stabilization of highway and roadway embankments and cut slopes
- Tunnel portals in unstable and steep stratified slopes
- Construction and retrofitting bridge abutments
- Steep cutting stabilizations
- Stabilizing of over steep existing embankments
- Provide long term stability to existing concrete structures without demolition and rebuilding costs
- Lastly, temporary excavation shoring
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Jet Grouted Soil Nailing Method
- In jet grouted soil nailing method, jets are used for eroding the soil for creating holes in the slope surface.
- After that, steel bars are installed in this hole and grouted with concrete.
- Finally, jet grouted soil nailing provides good corrosion protection for the steel bars .
Fig.9:Jet grouting soil nail method
Launched Soil Nails In Slide2
As long-time users of Rocscience geotechnical analysis tools, the design-build teams at GeoStabilization International are excited about the many updates and improvements to Slide2, one of the most comprehensive slope stability analysis programs on the market. GeoStabilization engineers have been serving as beta testers of the new program, exploring the new features and capabilities. The inclusion of the Launched Soil Nail support type as one of the types available for designers in Slide2 will save engineers that design with these elements many hours of tedious iterations required in older design processes.
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Numerical Analysis Results And Discussion
Sensitive analysis for five different slope and soil nail parameters was carried out. Considered variables in this analysis were slope inclination , nail spacing , nail inclination , and nail head size are summarized in Table 4. Since each slope angle had 120 models based on the number of each variation of parameters then 480 simulations were conducted in total. In this study, 1.5 of minimum factor of safety was chosen for the verification in the reinforced slope by soil nail . And then the result of soil nailed slope stability with flexible facing systems was presented in terms of a combination of soil nail parameters.
Table 4 The variation range of soil nail parameters
Soil Nails For Roadways
Soil nails are used throughout the country on a wide variety of projects involving roadways. These projects range from local municipality roads all the way up to large-scale DOT projects. Applications for soil nails include roadway cuts, roadway widening, tunnel portals, and repairing existing retaining structures such as bridge abutments, just to name a few.
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Design Of Soil Nail Walls: Construction Advantages And Disadvantages
Soil nail walls consists of installing passive reinforcement in existing ground by installing closely spaced steel bars or sections and placing a front face support. Soil nails are later grouted if they are installed in drilled holes. Ungrouted soil nails are also possible if nails are driven into the ground. Figure 1 shows typical details of a soil nail wall:
Figure 1: Typical soil nail wall arrangement
SNAILPlus soil nailing software, used by TX-DOT, WA-DOT and more!
FHWA Equations included in Report!
Soil nail wall construction proceeds from the top to bottom, and head plates are installed on each nail. Shotcrete or concrete is typically applied on the excavation face to provide continuity when a soil nail wall is constructed. For a soil nail wall the general construction procedure involves:
a) Excavate for the first nail
b) Install the 1st nail.
c) Construct 1st phase shotcrete on soil face with wire mesh or other reinforcement if required.
d) Install soil nail head plate
e) Construct 2nd phase shotcrete .
f) Excavate to next soil nail level, and install next soil nail, shotcrete etc.
g) Repeat steps c) through f) until the final excavation level is reached.
h) Construct additional permanent facing if required.
* Drainage filters and drainage pipes are also commonly installed during construction.
Figure 2: Typical soil nail head plate and shotcrete details
Soil nailing has proven economically attractive and technically feasible when:
What Is Soil Nailing
An engineered method to remediate unstable natural slopes or construct new or existing over-steepened slopes, the soil nailing process consists of inserting thin reinforcing elements into slopes. The practice involves drilling solid or hollow bar components to depths specified by a geotechnical engineer. GeoStabilizations innovative Soil Nail Launcher utilizes compressed air to blast up to 20-foot-long nails into the slope at speeds reaching 250-mph.
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Launched Soil Nail Concept
Launched soil nails are a proven technology that allows rapid stabilization of shallow landslides in soil. Tens of thousands of launched soil nails have been installed in the U.S., Canada, U.K., New Zealand, and Australia. Utilizing what has been termed as a nail gun on steroids, GeoStabilization and its partner companies launch soil nails into the ground to reinforce an unstable or potentially unstable soil mass by transferring the nails tensile and shear capacity into the sliding soil. These 1.5-inch-diameter, up to 20-feet-long nails are installed in a single shot using a compressed air cannon at velocities of up to 250 miles/hour, and at rates approaching 250 nails/day.
The single impulse, high-installation velocity creates a shock wave at the nail tip, which displaces the adjacent soil as the nail penetrates. The compressed air cannon induces tensile stresses in each tube as it penetrates the ground. This tension counteracts the compressive stresses induced by the displaced soil and thereby prevents nail buckling.
The typical launched soil nail consists of three parts:
Driven Soil Nailing Method
- It is used for temporary stabilization of soil slopes.
- Driven soil nailing method is considerably fast.
- However, it does not provide corrosion protection to the reinforcement steel or nails.
- In driven soil nailing method, the nails are driven in the slope face during excavation.
- Diameter of the nail is around 19mm to 25mm which is comparatively small.
- Lastly, nail spacing is 1m to 1.2m.
Fig.7:Driven soil nail method
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Drilled And Grouted Soil Nailing Method
- In this type of soil nailing methods, the holes are drilled in walls or slope face
- Then, nails are inserted in the pre-drilled holes.
- after that, the hole is filled with grouting materials such as concrete, shotcrete etc.
- Finally, diameter of nails ranges from 100-200mm with spacing of 1.5m.
Fig.6:Drilled and grouted soil nailing method
