Yes, there are methods to repair broken terra cotta/clay duct banks without removing the existing cables, and your idea using a split PVC conduit as a sleeve is a viable option. Here's a breakdown of the procedure and considerations

General Approach

The core idea is to:1. Assess the Damage

Determine the extent of the break in the terra cotta duct. How much is missing or crumbled? This will influence the size and length of the repair section.2.

Clean and Stabilize

Carefully remove loose debris and any crumbling terra cotta around the break. You might need to temporarily support the existing cables to prevent further damage.3.

Create a Sleeve/Encasement

This is where the split PVC comes in.4.

Install and Secure the Sleeve

Position the sleeve around the cables and into the remaining duct.5.

Seal and Backfill

Fill any gaps and secure the repair to prevent water ingress and maintain structural integrity.

Detailed Procedure Using Split PVC Conduit

This is a practical method you suggested:1. Safety First



De-energize if possible

Consult with the utility or appropriate authority to see if you can temporarily de-energize the cables. This is the safest option, but often not practical.

If energized

Treat the cables as live. Use insulated tools and wear appropriate PPE (rubber gloves, insulated sleeves, etc.). Have a qualified electrician present to oversee the work, if possible.

Grounding

Ensure proper grounding procedures are followed.

Excavation Safety

If underground, follow all trenching and excavation safety guidelines.2.

Excavation and Access (if underground)

Carefully excavate around the damaged duct bank section to expose the break. Dig wide enough to comfortably work. Shore the excavation if necessary to prevent collapse. Consider using hand tools (shovels, picks) close to the duct bank to avoid damaging the cables.3.

Preparation



Clean

Thoroughly clean the inside of the existing terra cotta duct bank on either side of the break. Remove any dirt, debris, or loose fragments.

Stabilize Cables

If the break is significant and the cables are sagging or unsupported, use temporary supports (straps, blocks) to hold them in place. Be very gentle.

Measure

Accurately measure the outside diameter of the cables and the inside diameter of the terra cotta duct. This will help determine the appropriate size of PVC conduit.

Select PVC Conduit

Choose a rigid PVC conduit of a sufficient diameter to comfortably accommodate the cables with some clearance. Consider schedule 40 or 80 depending on the anticipated stress and soil conditions. Ensure the conduit is rated for underground use.

Cut and Split PVC

Cut the PVC conduit to the necessary length to cover the damaged section and extend a reasonable distance into the existing duct on both sides (e.g., 6-12 inches, depending on the damage). Carefully split the PVC conduit lengthwise into two halves. Use a saw designed for cutting PVC, and take care to make clean, even cuts.

Smooth any sharp edges after cutting to prevent damage to the cable insulation.4. Installation



Trial Fit

Before applying adhesive or sealant, do a dry run to make sure the PVC halves fit around the cables and slide easily into the existing terra cotta duct. You may need to slightly widen the split if the cables are tightly packed.

Position and Assemble

Carefully position one half of the split PVC conduit around the cables. Then, carefully position the other half. Ensure the halves are aligned properly.

Secure the PVC Halves

Temporarily secure the PVC halves together using cable ties or strong tape. This will hold them in place while you move on to the next step.

Slide into Duct Bank

Gently slide the assembled PVC sleeve into the existing terra cotta duct on both sides of the break. Work carefully to avoid snagging or damaging the cables.5.

Sealing and Backfilling



Seal Gaps

Use a flexible, waterproof sealant (e.g., silicone sealant or polyurethane-based sealant designed for underground applications) to seal the gaps between the PVC sleeve and the existing terra cotta duct on both ends. Also, seal along the seam where the two PVC halves meet. This is crucial to prevent water from entering the duct.

Support and Secure

Add external support to the sleeve. You can secure it using duct tape wrapped around the sleeve and attached to the terra cotta duct, or using zip ties around the sleeve and duct.

Backfill (if underground)

Carefully backfill the excavation with suitable material (e.g., compacted soil, sand). Avoid using large rocks or sharp objects that could damage the PVC sleeve or cables. Compact the backfill in layers to prevent settling.

Important Considerations



Cable Spacing

Ensure there's adequate spacing between the cables within the PVC sleeve to prevent overheating. If the cables are tightly packed, this method might not be suitable.

Duct Bank Configuration

The specific configuration of the duct bank (number of ducts, spacing) will influence the ease of the repair.

Heat Dissipation

Replacing clay duct with PVC can slightly alter the heat dissipation characteristics of the duct bank. This is usually not a significant issue for short repair sections, but it's something to be aware of, especially for high-voltage or heavily loaded cables.

Alternatives

Other repair methods might be more appropriate depending on the situation. For example, if the damage is minor, you might be able to patch the terra cotta with a suitable mortar or epoxy. For more extensive damage, you might need to expose a larger section of the duct bank and replace the damaged section with a complete PVC duct section (which would require cutting and splicing the cables – a more complex and risky procedure). Epoxy resins specifically designed for concrete or clay repair are also available, but they may be difficult to apply properly around energized cables.

Consult with Experts

It's always a good idea to consult with a qualified electrician or civil engineer experienced in underground utility work before attempting this type of repair. They can assess the specific situation and recommend the best approach.

Advantages of Using Split PVC



No cable removal

This is the biggest advantage, as it avoids the complexity and risk of cutting and splicing cables.

Relatively simple

The installation process is relatively straightforward.

Waterproof

PVC is inherently waterproof, and with proper sealing, the repair can provide good protection against water ingress.

Durable

PVC is a durable material that can withstand underground conditions.

Readily Available

PVC conduit is readily available and relatively inexpensive.

Disadvantages



Heat dissipation

PVC is a less effective heat conductor than terra cotta.

Space constraints

Tight spaces can make it difficult to maneuver the split PVC sections into place.

Sealing is critical

Improper sealing can lead to water ingress and premature failure of the repair.

In summary, using a split PVC conduit to sleeve a damaged terra cotta duct bank is a feasible and practical repair method, as long as you take the proper safety precautions, carefully follow the procedure, and ensure proper sealing. Always prioritize safety and consult with qualified professionals when working with energized cables. Flag for review