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Soil Nail Walls��Module 4: Construction Inspection Activities

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Introduction

Training support files are available as attachments from the resources link.

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Course Map

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Course Map

Module 1

Module 2

Module 3

Module 4

Module 5

Introduction to Soil Nail Walls

Fundamentals of Soil Nail Walls

Pre-Construction and Construction

Construction Inspection Activities

Testing and Monitoring

Production: Please add relevant icons for each module. Do not use the example shown for Module 3.

Construction Inspection Activities

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Module Overview

This module will take approximately 60 minutes to complete.

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Module Overview

Excavation and Drilling

Nail Installation and Grouting

Initial Wall Facing

Construction Inspection Activities

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Module Learning Outcomes

Upon completion of this module, you should be able to:

Summarize the key inspection activities involved in the excavation and drilling steps of soil nail wall construction
Describe the key inspection activities involved in the nail installation, grouting, and drainage steps of soil nail wall construction
Summarize the key inspection activities involved in construction of the wall facing for a soil nail wall

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Module Learning Outcomes

Construction Inspection Activities

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Pre-Construction and Inspection

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Constructional Inspection Activities

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Hello again! Welcome to this active construction site…

Select the “Enter Site” box to get started.

ENTER SITE

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Construction Inspection Activities

Script (Jake): Hello again! Welcome to this active construction site. In the previous module, you explored the inspector's role in pre-construction and materials inspection. Now, you’ll join me as we go on a detailed exploration of the inspection activities at each step of active soil nail wall construction. Don’t forget to wear your hard hat! Select the “Enter Site” box to get started.

Production: Recreate an animated sequence.

Navigation: The user selects the “Enter Site” box to advance to the next slide.

Image: Man in a hard hat and vest looking official with clipboard

Source: Articulate

Image: Workers and business people

Source: iStock ID: ID:164852831 https://www.istockphoto.com/photo/workers-and-business-people-walking-in-quarry-gm164852831-164852831?searchscope=image%2Cfilm

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Construction Inspection Activities

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Step 1 - Excavation

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Production: This image can be any construction background

You’ll recognize these six steps of top-down construction…

Select Step 1 – Excavation to learn…

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Construction Inspection Activities

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Construction Inspection Activities

Menu: [indent]

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 1 – Excavation

In Step 1, excavation is done in stages if more than one row…

Wall face

Proper excavation of the wall face…

As an inspector, your role is to monitor excavation height…

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SMEs, do you have an animation or short video clip to demonstrate?

Note: Ideally, all of the “See it” diagrams would be replaced with SME-provided animations or a set of pictures we could animate.

Construction Inspection Activities

Script (Jake): In Step 1, excavation is done in stages if more than one row of nails is required. Proper excavation of the wall face is essential to prevent sloughing—that's when loose soil starts to break away from the face. Careful excavation also helps avoid removing too much soil. The contractor is responsible for making sure excavation happens in the right location and at the correct levels. As an inspector, your role is to monitor excavation height, lift requirements, and elevation throughout the entire process.

Production: Recreate an animated sequence. Text boxes are highlighted as narrated.

Navigation: Users must toggle both “See It” and “Inspect It” to complete the steps.

Image: Figure 2.2. Typical soil nail wall construction sequence. Step 1- Excavate Initial Lift.

Source: FHWA GEC 007 February 2015

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Construction Inspection Activities

Menu: [indent]

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 1 - Excavation

Evaluate type, nature, and moisture condition of excavated materials and those present at the excavation face
Identify unexpected soft zones, seepage areas, or fill
Monitor for recurrent raveling or sloughing of the excavation face
Document condition of the excavation face at the start and end of each work day
Note which portions of the face have been left unprotected, if any
Verify stability of the retained soils, area behind or upslope of the wall, and the bottom of the excavation (at least twice daily)

Production: “X” appears only on Inspect It tab. Please improve design.

SMEs, do you have any photos we could use?

Construction Inspection Activities

Script (Jake): When you're inspecting the excavation phase, start by evaluating the soil conditions - look at the type, nature, and moisture level of the excavated materials, especially at the excavation face. You'll want to keep an eye out for any unexpected soft zones, areas with water seepage, or fill material that wasn't anticipated. Throughout the day, monitor the excavation face for any signs of raveling or sloughing - this is where small pieces of soil break away, which could indicate stability issues. It's really important to document the condition of that excavation face both at the beginning and end of each workday.

Make sure you note any portions of the face that have been left unprotected. And don't forget to verify the stability of all retained soils - check the area behind and upslope of the wall, as well as the bottom of the excavation. This needs to be done at least twice daily for safety.

Production: Pop up for Step 1 - Excavation

Navigation: User select X to return to steps menu. The X only appears on the Inspect It toggle.

Image: Figure 2.2. Typical soil nail wall construction sequence. Step 1- Excavate Initial Lift.

Source: FHWA GEC 007 February 2015

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Construction Inspection Activities

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Drilling of the Nails

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 2 – Drilling of Nails

SMEs, do you have an animation or short video clip to demonstrate?

Steel Casing

Used in unstable soil

Drilling Equipment

Rotary or percussion

Drill Angle

Slightly downward

Nail Spacing

Typically 5 ft apart

Drilled Hole

Diameter and depth must match the design

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Uncased

Used in stable soil

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Construction Inspection Activities

Script (Jake): In Step 2, holes are drilled for the soil nails. You might see either rotary drilling, which cuts through soil by spinning, or percussion drilling, which breaks up soil by hammering. Depending on the ground conditions, the contractor may drill with a steel casing to support the hole, or they may leave the hole uncased if the soil is stable enough. The angle of the drill is important—it should be slightly downward, as shown in the project plans, not horizontal. This ensures the nails are positioned to properly reinforce the retained soil.

Inspectors should observe the diameter and depth of the hole—these need to match the design exactly. Nails are typically spaced about 5 feet apart both vertically and horizontally, but your plans may specify different spacing.

Before continuing with the installation, some of the drilled holes will be used for testing. These include proof tests to verify load capacity and creep tests on designated sacrificial nails to evaluate long-term performance under sustained load

Production: Recreate an animated sequence. Text boxes are highlighted as narrated

Navigation: Users must toggle both “See It” and “Inspect It” to complete the steps

Image: Drill Holes (in color)

Source: https://www.spargrp.com/soil-nailing/

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Construction Inspection Activities

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Drilling of the Nails

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 2 – Drilling of Nails

Note equipment and installation method
Check drill fluid pressure, flow rate, and volume
Watch for ground subsidence above drill location
Look for excess soil removal with little drill progress
Record drill method, bit type, casing diameter and length, drill string length, and fluid type
Measure drill bit, string, and casing before drilling
Record final hole length after flushing
Track how long hole stays open before tendon insertion

SMEs, do you have any photos we could use?

Construction Inspection Activities

Script (Jake): When inspecting the drilling phase, first document what equipment and installation method is used by the contractor. Pay attention to the drilling fluid - its pressure, flow rate, and volume. These factors need to be controlled carefully to keep the drilling moving while avoiding problems in the surrounding soil. Watch the ground surface above where the drilling is happening. Any sinking of the ground (known as subsidence) could signal an issue. Also note if large quantities of soil are being removed with little or no advancement of the drill head. You'll need to record all the technical details - the type of drilling method and tools used, including drill bit type, casing diameter if one is being used, final length of casing, length of drill string, and the type of drilling fluid being used. When possible, observe the soil cuttings and note any areas where drilling seems particularly difficult or easy. Before drilling starts, measure the length of the drill bit, drill string sections, and any casing sections. After the hole is flushed, record its final length before tendon insertion.

Track how long each drill hole is left open before the tendon is inserted. Holes shouldn't remain open for long periods - ideally, the tendons should be inserted and grouted right after drilling to prevent water seepage or cave-ins

Production: Pop up for Step 2 – Drilling of nails

Navigation: User select X to return to steps menu. The X only appears on the Inspect It toggle.

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Construction Inspection Activities

Menu: [indent]

Nail Installation and Grouting

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 3 – Nail Installation and Grouting

SMEs, do you have an animation or short video clip to demonstrate?

In part one, the steel tendon is placed into the drilled hole along with a tremie grout pipe…

…it fills up the space around the outside of the tendon

In part two, the strip drains are installed…

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Construction Inspection Activities

Script (Jake): In part one, the steel tendon is placed into the drilled hole along with a tremie grout pipe. Grout is poured into the top of the pipe, and gravity helps it flow down to the bottom of the hole. As more grout is added, it fills the space around the outside of the tendon. Any air, water, or leftover drilling material is forced up and out of the hole. Grout can also be placed with a low-pressure pump of less than 10 pounds per square inch to help it flow more steadily.

Then, in part two, the strip drains are installed. These are long, vertical drainage strips placed against the excavation face. They go between adjacent nails and are installed as the wall is excavated, one lift at a time. At each stage, more of the same strip is unrolled, extending it slightly below the bottom of the current lift. By the time excavation reaches the bottom of the wall, each strip forms one continuous path from the top of the wall all the way to the base.

Production: Recreate an animated sequence. Text boxes are highlighted as narrated

Navigation: Users must toggle both “See It” and “Inspect It” to complete the steps

Image: Drill Holes (in color)

Source: https://www.spargrp.com/soil-nailing/

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Construction Inspection Activities

Menu: [indent]

Nail Installation and Grouting

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 3 – Nail Installation and Grouting

Confirm correct nail are being used
Check bar size and length, corrosion protection and centralizers
Verify centralizers are spaced according to specs and securely attached to the tendon

Check grout consistency and identify if mix appears too thin or watery
Report any issues to your team or engineer
Confirm the hole is grouted withing the required time after drilling
Confirm grout placement and coverage is reached

Confirm wall batter matches design plans (vertical or sloped)
Confirm nail inclination follows the wall batter.
Verify nails are aligned with the slope of the wall

Confirm strip drains are:

Spaced according to plans
Facing the correct direction
Attached securely (stapled or pinned)
Installed per manufacturer’s instructions

SMEs, do you have any photos we could use?

Nail Installation

Wall Batter

Grouting

Drainage

Construction Inspection Activities

Script (Jake): When inspecting Step 3, you'll check four key areas: nail installation, wall batter, grouting, and drainage. Start by confirming that the correct nails are being used. Check the bar size, length, corrosion protection, and the use of centralizers. Centralizers help keep the nail centered in the hole. They must be spaced according to the specs and securely attached to the tendon, usually with tie wire, because they can shift as the nail is inserted.

Next, check that the wall batter matches the design plans. Some walls are built vertical, while others have a slight batter which means they lean back away from the excavation. This impacts the soil nail placement. For example, a 10:1 batter means the wall leans back 1 foot horizontally for every 10 feet of height. Confirm the nail inclination follows that wall batter. The nails should be aligned to match the wall’s slope.

Next, check the grout. Daily samples are usually sent to a lab to test compressive strength. You won't be collecting the samples, but you can still catch problems early in the field.

Keep a visual check on the grout’s consistency. If it looks thin or watery, the water-to-cement ratio might be off. Let your team or an engineer know if you see anything unusual.

Also, confirm the hole is grouted within the required time. For example, CDOT requires grouting within two hours of drilling. Grout is placed using a tremie tube which is a long PVC pipe connected to a grout hose. It should fill the hole from the bottom up and flow out the face of the nail when complete. If there’s groundwater in the hole, you may first see water or watery grout being pushed out. Keep an eye on the flow to confirm when full grout coverage is reached.

Finally, inspect the strip drains. These are corrugated plastic strips wrapped in fabric and placed against the excavation face. Make sure they’re spaced correctly, facing the right direction, and installed securely, usually stapled or pinned in place. They must follow the manufacturer’s installation instructions.

Production: Pop ups for Step 3 – Nail installation and grouting. Users select each area (e.g. nail installation, wall batter, grouting, and drainage) to trigger another pop up of the checklist for that area.

Navigation: User select X to return to steps menu. The X only appears on the Inspect It toggle.

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Construction Inspection Activities

Menu: [indent]

Construction of the Initial Shotcrete Facing

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 4 – Construction of the Initial Shotcrete Facing

SMEs, do you have an animation, short video clip, or photos to use here

…an initial shotcrete facing is applied to the exposed surface.

Welded-wire mesh is placed in the middle of the layer…

…a steel bearing plate is pressed into the fresh shotcrete…

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Construction Inspection Activities

Script (Jake): In Step 4, construction shifts from installing soil nails to building the wall facing. The initial shotcrete facing supports the exposed soil between the nails and the excavation face. It keeps the wall stable as excavation continues and helps tie all the components together into one system. Before the next lift of soil is excavated, an initial shotcrete facing is applied to the exposed surface. This layer is usually about 4 inches thick, though that can vary depending on the design. The shotcrete is lightly reinforced. Welded-wire mesh, or WWM, is placed in the middle of the layer, and extra horizontal and vertical bars are added around the nail heads for bending resistance.

As the shotcrete begins to cure, a steel bearing plate is pressed into the fresh shotcrete over the exposed tendon. This is called a wet set. Then, a washer and hex nut are added to hold the nail head in place. The hex nut should be wrench-tightened within 24 hours. Before excavation can continue, the shotcrete needs time to cure. It must reach its minimum 3-day compressive strength—usually about 72 hours. Depending on the project requirements, some of the installed nails may need to be proof tested at this stage to confirm their capacity or meet load criteria.

Production: Recreate an animated sequence. Areas on diagram are highlighted as narrated

Navigation: Users must toggle both “See It” and “Inspect It” to complete the steps

Image: Place temporary facing – Step 4 (in color)

Source: https://www.spargrp.com/soil-nailing/

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Construction Inspection Activities

Menu: [indent]

Construction of the Initial Shotcrete Facing

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 4 – Construction of the Initial Shotcrete Facing

The full inspection checklist comes after Step 6, but here’s a closer look at a few key details from Step 4.

Select each item to learn more

The steel bearing plate is pressed into the fresh surface while it’s still curing. A washer and hex nut are added to secure the nail head.

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Welded wire mesh is placed before shotcrete is applied.

Construction Inspection Activities

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Construction Inspection Activities

Menu: [indent]

Construction of Subsequent Levels

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 5 – Construction of Subsequent Levels

SMEs, do you have an animation, short video clip, or photos to use here

…the same process you saw in Steps 1 through 4 is repeated…

At each level, the strip drain is unrolled downward…

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Construction Inspection Activities

Script (Jake): In Step 5, the same process you saw in Steps 1 through 4 is repeated for the next excavation lift—and for every lift after that. At each level, the strip drain is unrolled downward so it continues to the next lift. This creates one continuous drainage path behind the wall. A new panel of wire mesh is installed, overlapping the panel above it by at least one full mesh cell. Then, shotcrete is applied again, connecting with the previous lift’s facing.

This process is repeated—excavate, install nails and drains, apply shotcrete—until the wall reaches its full height.

Production: Recreate an animated sequence. Areas on diagram are highlighted as narrated

Navigation: Users must toggle both “See It” and “Inspect It” to complete the steps

Image: Construction of Subsequent Levels– Step 5

Source: https://www.spargrp.com/soil-nailing/

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Construction Inspection Activities

Menu: [indent]

Construction of Subsequent Levels

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 5 – Construction of Subsequent Levels

The full inspection checklist comes after Step 6, but here’s a closer look at a few key details from Step 5

Select each item to learn more

Each new welded-wire mesh panel must overlap the one above it by at least one full mesh cell. This keeps the facing reinforced between lifts.

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SMEs, do you have a photo of a new welded-wire mesh panel being placed below a previous one?

SMEs, do you have a photo showing the strip drain being extended to a new lift?

At each new lift, the strip drain is unrolled downward to continue the drain path.

Construction Inspection Activities

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Construction Inspection Activities

Menu: [indent]

Construction of the Final Facing

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 6 – Construction of the Final Facing

SMEs, do you have an animation, short video clip, or photos to use here

In step 6, construction wraps up with the final facing.

These can include weepholes, a foot drain at the base, and drainage ditches.

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Construction Inspection Activities

Script (Jake): In Step 6, construction wraps up with the final facing. This happens after the wall reaches its full height and all soil nails have been installed and tested.The final facing provides long-term protection and appearance. It may be made of cast-in-place reinforced concrete, reinforced shotcrete, or prefabricated panels, according to the project plans. If reinforcement is required, rebar can be tied to the bearing plates using welded studs. Finally, drainage components are added to carry water away from the wall. These can include weepholes, a foot drain at the base, and drainage ditches. Together, they help discharge water collected in the strip drain system.

Production: Recreate an animated sequence. Areas on diagram are highlighted as narrated

Navigation: Users must toggle both “See It” and “Inspect It” to complete the steps

Image: Construction of Subsequent Levels– Step 6 (in color)

Source: https://www.spargrp.com/soil-nailing/

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Construction Inspection Activities

Menu: [indent]

Construction of the Final Facing

Excavation

Drilling

Installation

Initial Facing

Subsequent Levels

Final Facing

Inspect It

See It

Step 6 – Construction of the Final Facing

Confirm the nozzleman is experienced and certified if required
Verify shotcrete depth, rebar spacing, coverage, and nail head hardware
Check that shotcrete is placed from the bottom up
Check there are no voids behind mesh, rebar, and bearing plates
Confirm wall surface has clean edges and accurate lines
Verify weather conditions are acceptable or properly managed

SMEs, do you have 3-4 high quality photos of completed soil nail walls?

Construction Inspection Activities

Script (Jake): The inspection checks you see here include Steps 4 through 6 because they all relate to the wall facing. While some items are checked during each lift, others are easier to confirm once the full wall is constructed at Step 6. Confirm that the nozzleman applying the shotcrete is experienced, and certified or prequalified if required. Verify that the shotcrete has the specified depth, rebar spacing, coverage, and nail head hardware. Check that shotcrete placement begins at the bottom of each lift. Check to be sure there are no voids behind mesh, rebar, and bearing plates. These elements should be fully embedded with no gaps. Confirm that the wall surface has clean edges and accurate lines, shaped using screen boards, guide wires, or spacers. Verify that weather conditions are acceptable during shotcrete application. If conditions are poor, confirm that appropriate mitigation measures are in place.

Production: Pop up for Step 6– Construction of the Final Facing

Navigation: User selects X to close and auto advance to the next slide if all six steps have been explored.

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Limitations of Soil Nail Walls

Read each description below and choose the step number that matches the activity being described. Write your answer in the provided box. Select Submit when you’re satisfied with your answers.

Menu:

Knowledge Check – Name that Step!

Submit

Description	Step Number (your answer)
A). A new mesh panel overlaps the one above, and shotcrete connects with the previous layer.
B). Grout is placed from the bottom up using a tremie tube.
C). The wall is excavated one lift at a time to expose a fresh face for drilling
D). After all nails are installed, the final facing and drainage features are installed.
E). Holes are cleaned and centralizes are placed on the tendon before it’s inserted.
F). Shotcrete is applied, and a bearing plate is pressed into place over the wall.

Answer Choices

Step 1 – Excavation

Step 2 – Drilling of Nails

Step 3 – Nail Installation and Grouting

Step 4 – Construction of Initial Facing

Step 5 – Construction of Subsequent Levels

Step 6 – Construction of Final Facing

Construction Inspection Activities

Script (Jake): You’ve just explored all six steps of the soil nail wall construction process, along with the key inspection activities that go with them. Great job! Do you think you can spot what’s happening at each stage now? Let’s find out in this next knowledge check. It’s time to play Name that Step!

Read each description below and choose the step number that matches the activity being described. Write your answer in the provided box. Select Submit when you’re satisfied with your answers.

Production: Knowledge check where participant select the correct construction step to match the description. Up to two incorrect attempts before debriefing. Correct answers are Step 5 / Step 3 / Step 1 / Step 6 / Step 2 / Step 4

Navigation: User writes their answer in each box and then selects Submit.

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Limitations of Soil Nail Walls

Read each description below and choose the step number that matches the activity being described. Write your answer in the provided box. Select Submit when you’re satisfied with your answers.

Menu: [Indent]

Name that Step - Debrief

Submit

Description	Step Number (your answer)
A). A new mesh panel overlaps the one above, and shotcrete connects with the previous layer.
B). Grout is placed from the bottom up using a tremie tube.
C). The wall is excavated one lift at a time to expose a fresh face for drilling
D). After all nails are installed, the final facing and drainage features are installed.
E). Holes are cleaned and centralizes are placed on the tendon before it’s inserted.
F). Shotcrete is applied, and a bearing plate is pressed into place over the wall.

Step 5

Step 3

Step 1

Step 6

Step 2

Step 4

Answer Choices

Step 1 – Excavation

Step 2 – Drilling of Nails

Step 3 – Nail Installation and Grouting

Step 4 – Construction of Initial Facing

Step 5 – Construction of Subsequent Levels

Step 6 – Construction of Final Facing

Construction Inspection Activities

Script (Jake): How did you do? Let’s check your answers:

Description A described a new mesh panel overlapping the one above, and shotcrete connecting with the previous layer. That’s Step 5 – Construction of Subsequent Levels.

Description B was about grout being placed from the bottom up using a tremie tube. That’s Step 3 – Nail Installation and Grouting.

Description C explained how the wall is excavated one lift at a time to expose a fresh face for drilling. That’s Step 1 – Excavation.

Description D mentioned that after all nails are installed, the final facing and drainage features are added. That’s Step 6 – Construction of Final Facing.

Description E was about cleaning the holes and placing centralizers on the tendon before insertion. That’s Step 2 – Hole Cleaning and Nail Placement Prep.

Description F described shotcrete being applied, and a bearing plate being pressed into place over the wall. That’s Step 4 – Construction of Initial Facing.

Production: Example debrief layout. Make it as clean and readable as possible

Navigation: Users select “Next” to advance to the next slide

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Learning Outcomes

You should now be able to:

Identify the key responsibilities of an inspector in the construction of soil nail walls
Recall the key activities related to pre-construction preparation and materials inspection of soil nail walls
List the key steps in a typical soil nail wall construction sequence

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Learning Outcomes

Construction Inspection Activities

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Summary

This concludes Module 4: Construction Inspection Activities

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Module Complete

You have reached the end of this module.

Select the next module to continue.

Construction Inspection Activities