Herns Lane, Welwyn Garden City | Piling Contractors | Keller UK

Herns Lane, Welwyn Garden City

Compaction Grouting
The process is the injection of a very stiff, low slump mortar type grout under relatively high pressures to displace and compact the soils in place.  Grout casings are installed in a pre-determined design pattern and grout is injected to form homogeneous bulbs as the casings are extracted.

Contract Statistics
Number of Compaction Grout Holes – 551no
Total Metres Drilled – 9929m
Number of 1.0m Stages Injected – 5705no
Total Volume of Compaction Grout Injected – 1995m3

Keller Geotechnique were contracted by Crest Nicholson, working on behalf of the National House Building Council (NHBC), to carry out Compaction Grouting Works to Chalk Solution Features identified below the proposed footprint of New Build Properties at Black Fann Road/Herns Lane, Welwyn Garden City.

2no x Klemm 708 tracked drilling rigs were utilised for the works encompassing a 114mm diameter drill casing and sacrificial/lost point drill bit, Due to the estimated quantities of Compaction Grout required KG utilised Ready Mix Compaction Grout (a stiff low slump mortar like grout) from local suppliers. Volumes in excess of 80-90m3 per day were injected.

Validation of the Compaction Grouting Works was carried out by using Dynamic Probing techniques (Super Heavy Dynamic Probing DP-SH).  Where areas were found to have low blow counts, additional holes were drilled and grouted and further Dynamic Probes were carried out. A few areas still showed low blows and again were re-drilled and grouted.

System: Compaction Grouting

Client: Crest Nicholson

Contractor: Keller Geotechnique

Engineer: Reuby & Stagg


Case Studies