Precast Concrete Products

Introduction

The Vanstone Panel Manhole is a kit-form light duty precast concrete inspection / service chamber suitable for underground telecoms services.

The kit consists of a base or floor, 4 wall panels and a lid section including a cast iron cover and frame. The wall spanels have a total of 28 convenient knock-outs for service entry.

Dimensions:

• Inside: 600 x 600 x 700mm deep
• External: 780 x 780 x 770mm height
• Wall thickness: 65mm
• Weight (total): 385kg

Service entry holes:

• North-South: 8 x 110mm and 2 x 75mm diameter
• East-West: 4 x of 110mm diameter
• Base: 1 x 40mm diameter drainage hole.

Click here for detail of knock-out holes

Without CI cover

Installation

The total external height of the manhole is 770mm. It is often preferred that the rim of the manhole project above the ground or paving by at least 75mm. This determines the depth of excavation. Excavate for the manhole and over-excavate for the sides sufficiently to allow for compaction equipment. Where sufficient accuracy of excavation can be achieved, only slight over excavation is required, which may be backfilled with a cement stabilized gravel or mass concrete if preferred.

Backfilling should always be at least as strong and serve the same purpose as the surrounding soil. To aid the drainage of occasional rain water, a subsoil drain may be installed under the manhole. This can be in the form of a small sump under the centre hole that can hold extra water or a system that drains water away from the manhole. Simply over-excavate to the size required and fill with any constant size crushed stone.

In the bottom of the excavation, prepare a true and level 50mm thick bed of riversand, crusher sand, fine clean gravel (particle size < 6mm) or cement stabilized topping material. Place the manhole base or floor carefully on the bed ensuring proper and even seating. Place the wall panels on the base, ensuring that the panels are the right way up and facing the right way when looking at the service holes. Knock-out dimples should face inward. The panels sit on the edge of the base panel and fit into each other's corner recesses. See picture above. Hold the walls upright and make sure that the wall tops are together at the corners. Place the lid surround (frame) on top of the walls and make sure that all the wall tops fit into the recess underneath the surround. Once the lid surround is securely in place, the necessary holes for service entry can be knocked out carefully. Use a steel hammer (4lbs max.) and knock from the outside in. Do not use excessive force. The knocking-out may be done before the manhole is assembled but the risk is wrong orientation of holes or even breaking of a panel. The manhole can now be used to install sleeves, cables and other services.