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Civil Engineering Projects

2No 32m² tunnels x 1,000m long each, 6m high x 5m wide (concrete lined). Included circa 100m re-lining of existing tunnels.
S.A.T.S. Engineer: S.A.T.S. Reference: J. Hoffmeyer. Sub Contracted to Buccimazza, Pompei & Bassi. Trackless Drill & Blast. Duration 30 months

2No 32m² tunnels x 500m long each, 6m high x 5m wide (concrete lined)
S.A.T.S. Engineer: S.A.T.S. Reference: A. Vernetti of Torro (Pty) Ltd. Sub Contracted to Torro (Pty) Ltd. Trackless Drill & Blast . Duration: 16 months

2No 32m² tunnels x 250m long each, 6m high x 5m wide (concrete lined)
S.A.T.S. Engineer: S.A.T.S. Reference: G. Frederici of Imprefed. Sub Contracted to Imprefed of Italy. Trackless Drill & Blast. Duration: 10 months

Consulting – Tunneling method of work & equipment selection
MTR Contract 406 & 407. Main Contractor: Paul Y Construction. Reference: J. Blake. 7,000m long, 32m2 tunnels, concrete lined. Our mandate was to prepare the method of work and cycle times including the selection of plant and personnel requirements.

32m² tunnel x 400m long, 6m high x 5m wide (concrete lined)
S.A.T.S. Engineer: S.A.T.S. Reference: D. du Toit. Trackless Drill & Blast. Duration: 7 months

7,000m long, 3.35m high x 3.1m wide (dolomitic aggregate concrete lined)
City Council of Johannesburg. Engineer: Design Branch, Engineering Department, City of Johannesburg. Reference: D. Easton (LTA Construction). JV with LTA Construction. Drill & Blast – railbound equipment including ‘Grandori’ designed hoppers, headgear and tippler system. 10m2 tunnel traversing quartzites and lava at 1:1200 slope. Duration: 42 months.

3,800m long, 2.75m high x 2.6m wide
National Roads Department. Engineer: VKE. Reference: D. Hurter (LTA Construction). 50/50 JV with LTA Construction. Drill & Blast using railbound mucking equipment 7m2 tunnel. Just short of 100m from the portal the tunnel ran into a formation of mud which swept men and machines out of the tunnel – fortunately without injury. Bomar adopted ground freezing method to transverse this section (first time ground freezing used in South Africa). Duration: 24 months.

Consulting – Methodology, site personnel organisation and equipment selection
MTR Contract 430. Main Contractor: LTA/Marples Ridgeway. Reference: D. Easton Chief Estimator. Excavate 4 multi level underground basements adjacent to the Metro station. Area 5,145m2 with a total volume of 30,224m³. A vertical shaft and a system of orepasses plus the use of scraper shovels was the unlikely mix chosen, which proved very successful under difficult working conditions.

1,400m long x 2.6m high x 2.6m wide (Concrete lined 2m wide x 2m high)
Electricity Department, Johannsesburg Municipality. Engineer: City Engineers Department Reference: H.D. von Opple – Chief Engineer. Drill & Blast using railbound mucking equipment 6m2 tunnel at 1:68 gradient for electrical distribution cabling. Developed, in some sections only 2m below street level, under Jeppe and Delver Streets with extensive steel arch support. Duration: 20 months

120m long, 2.6m high x 2.6m wide (Concrete lined 2m wide x 2m high)
Rand Water Board. Engineer: Rand Water Board. Reference: Chief Engineer – RWB. Drill & Blast 6m2 tunnel and line with concrete pump remaining outside tunnel of the tunnel). Duration: 4 months.

500m long, 2.6m high x 2.6m wide (Concrete lined 2m wide x 2m)
Durban Corporation. Engineer: Durban Corporation. Reference: Mr. van de Linde. Drill & Blast 6m2 tunnel at 1% gradient. (Lined with pump remaining outside the tunnel). Duration: 10 months

Water Board. Engineer: KSI. Reference: F. Ilse. Sub Contracted to Clifford Harris. Bored 6m2 tunnel traversing under Westville University, 3800m long x 3.05m lined diameter. Duration: 24 months

Consulting – Ramp excavation methodology & costing
British Petroleum. Consultation on methods and cost for 1,000m long, 17.4m² long spiral ramp at 8 degrees and 2No, 400m long exploratory drives

5No vertical shafts, x/sectional area 15.75m² x 40m each deep
Mozambique Water Authority. Reference: A. Tamai, Chief Overseas Operations of CMC Italy. Sinking of shaft through weathered ground, spiling. Duration: 5 months

“Telex from italstrade, mozambique 14/10/84. We are happy to confirm that mario pietromartire has carried out exploration work inshaft for this company to our full satisfaction. Best regards – strade coop mozambico c.M. / italstrade regards / tamai”

Sink and line 2No, 7m x 5m elliptacle vertical shafts
Rand Water Board. Engineer: SRK. Reference: F. Jeffries-Director-Esor. Sub Contracted to Esor Ground Eng. (OFS side 36m deep, TVL side 65m deep) Accesses for tunnel development under the Vaal River. Drill & blast, mucking done with Eimco 630 when conditions permitted, lashing into kibbles hoisted by mobile cranes. Mesh reinforced shotcrete lined. Extremely poor ground conditions encountered with continuous grouting to minimise ingress of ground water. Duration: 14 months

Diversion Tunnel – 400m long, 9.2m high x 8m wide (68m²); Outlet Tunnel – 450m long 7.2m high x 8m wide (57m²), Penstock 6.5m wide x 4.25m high & concrete invert floors
Main Contractor – Komati Dam JV. Engineer: Consult4, Lahnmeyer, Swazi Group. References: P. Taylor – Project Manager, KDJV; Mr. Matchett of MDJV. 50/50 Joint Venture with Shaft Sinkers. Sub Contracted to KDJV. Full face drill & blast 4m long rounds using a 3 boom drill jumbo, pumpable emulsion explosives and electronic initiation. Broyt and Front end loaders and trucks for mucking. Steel arches, mesh & shotcrete support at the portals. Rockbolts ranging from 3m to 6m long and steel fibre shotcrete support. Best advance – 206m in one month. Duration 7 months.

Intake Shaft – 200m² x 21m deep vertical shaft and shotcrete line
An innovate and cost effective methodology was elaborated by Bomar to complete in the allowed time of 3 months. A drop-raised pilot hole was first blasted from the tunnel to surface. The shaft was then sliped, using the pilot hole to gravitate the rock to the tunnel below. Drilling with hand held jackhammers and for cleaning a scraper winch mounted on a custom designed turntable / frame was postitioned on top of the pilot hole with a tower crane and the blasted rock scraped to the pilot hole. A front end loader lrehandled the rock in the tunnel below. Duration 3 months.

2No Access Shafts & 605m long 2m high x 2m wide lined Tunnel
Johannesburg Water. Engineer: Goba-Keeve Steyn. References: GMKS -Trevor Nxumalo; Johanesburg Water – Paul Muller, Project Manager. Sub
Contracted to Cerimele-Phenduka JV. Drill & blast under residential areas – all blasts
controlled and monitored including PPV records. Concurrent dolomitic concrete lining. Tunnel excavated from both ends, both via access shafts equipped with heagears & hoisting gear. 150m of the tunnel required steel arch & lagging support. Railbound mucking equipment in tunnel. The invert concrete floor was cast after completion of tunnel excavation and crown lining. Duration 11 months.

760m long 3m high x 3m wide (2.7m high x 2.7m wide lined) Tunnel
Tshwane Metropolitan Council. VKE: References: C. Viljoen. Sub Contracted to Cerimele-Penduka JV. Concurrent dolomitic concrete lining. With the majority of the tunnel to be excavated through very hard quartzites (UCS in excess of 300MPa). Bomar opted to develop from one portal only using a heavy duty imported railbound twin boom drill-rig, complimented by Bomar’s HLS (Hopper Loading System) for fast cleaning. 150m of the tunnel required steel arch & lagging support. The invert concrete floor was cast after completion of tunnel excavation and crown lining. Duration 13 months.

Sinking, grouting, dewatering and civil works – 7m lined diameter deep foundation shafts – 6No for John Vorster Viaducts & 5No for Jean Avenue Viaducts
Bombela JV. Reference: S. De Boer – Project Director – North. Sub Contract. Design, fabricate, supply & install Temporary Works shaft stage platforms, winches, bank steelwork, kibbles, shutters, etc. Sink 8m diameter shafts from 17m to 35m deep. For blasting programmable electronic initiation was used. To mitigate wall in-stability in poor conditions while traversing dolomite formations, Bomar used conical formwork enabling pouring of fast set concrete at any time as temporary support that was kept at the bottom of the advancing shaft. A track drill-rig and hand held jackhammers were used for drilling. Unique blast protection screens installed on top of the shafts when blasting for safe blasting near structures and next to the highway so as not to interrupt traffic flow. Extensive probe / cover drilling and cavity grouting. Mini excavators were used for mucking into kibbles which were hoisted using 25t dedicated mobile cranes. Pumping of ground water inflows. Handling and fixing of wall rebar was facilitated by using custom AFrames. 80t cranes were used to lower pre-assemble shaft bottom rebar cages with mass of some 18t. For the final lining, cast from bottom up ready mix trucks delivered concrete to custom made shutters. Duration 12 months.