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Drilling, HDD and Pipelines

As the methodologies for underground installations works basically for installation of pipes may varies therefore there are a few acceptable methods to execute such activity.

Dalak Pipeline - Initial stage of design study for pipeline chambers and foundation

Open Trenching or Cut and Fill
This is the most basic method among all the later mentioned methods since it does not involved any complication except basic surveying work to ensure the trench excavated is parallel to the required/designated level. Upon completion of trenching, the desired installation are placed and then filled up to suitable level with endorsed suitable materials.

Another popular method is the shaft method where during manual excavation, a shaft shall be build to desired level and manual excavation will start to place. Although during modern era, this method has evolved to be part of the excavation processes rather than a single process coupled with manual human labor digging to build tunnels leading to proposed inlet and outlet.

During the modern years, tunneling has evolved from a manual shove armed labor to the deployment of Tunnel Boring Machines (TBMs) to undertake such hazardous job under the calculation and supervision of specialist. Depending on the soil conditions and risks, reinforcements shall be applied to avoid collapse of the wall during and after tunneling process(es). Aside from big TBMs there are microtunneling for smaller sizes boring work. These TBMs are controlled and monitored through various sensor and a graphic display will show the profile of the work and the position and the condition of the cutter head.

Pipejacking, as earlier said is a method of tunneling which emphasize on smaller pipes (up to 2400mm) under existing structures and/or installations. This procedure enable the pipes to be driven by mechanical means. At most time a shield or trust wall shall be constructed to provide reaction against of which to jack or namely the pressure by self weight or lateral pressure from the ground surface reacting against the jacking hole. In certain circumstances, this wall shall be structurally reinforced and strengthen. To ensure the jacking forces is distributed accordingly, a thrust ring is used to transfer the load. A minimal of two pit is needed for a basic pipejacking which are thrust pit and reception pit.

Horizontal Directional Drilling

In civil engineering especially in Malaysia, not many have come upon the technique called Horizontal Directional Drilling or HDD in short. It has been an advancement in tunneling and also the best alternative to the usual open trenching works for several engineering works namely pipe sleeves, pipeline, utilities conduit installation and also laying of cables. In Malaysia, there are several organizations which are well known for their provided services in this field of work.

It is good to understand that HDD is totally different comparing to pipesjacking works. While pipejacking method emphasize on  using driving force through various manner to thrust the specially design pipes into the ground simultaneously with the event of excavation manually or with machines.

Unlike the pipejacking method, the HDD method emphasize and deploys another method mechanism called the jet bit which set at the end of the pilot string. This equipment will bore a design path or pilot hole  as per designated profile through the ground avoiding all the barriers thus leads to minimal environmental disturbance surrounding it. Based on the bored path earlier, the pre-reaming and final reaming process(es) will take action where it will bore to size a path compatible with the size of the desired installation (pipe, sleeves or conduits) using a reamer. A pull-back pipe (or back ream) is installed behind the reamer and to be pulled to the intended end during the final reaming.

During this drilling process, viscous chemical (water and betonite or polymer) mixture known as drilling mud or drilling fluid which will lubricate passage of pipes, to stabilize the hole, to cool the drill bit and also to facilitate the drilling process during removal of cuttings.

The relevant issues of joint applications and deflections of the installation is reserved for future explanation under review sections. For more information and on how to design the drilling profile, please contact MCS.