Sensors and Soil Treatment at the Pantai Trunk Sewer in Kuala LumpurIn December 2003, the Sewerage Services Department under the Ministry of Energy, Water and Communication awarded the Shimizu-Road Builder-Hitachi Plant JV the contract to construct Phase 1, Package 1 of the sewage treatment plant project for Kuala Lumpur (KL). The contract involves the construction of a new sewer network (click here) and upgrading of five existing sewage treatment plants in and around KL. The Pantai trunk sewer forms the main pipeline to carry effluent which is collected by the network to the largest of the treatment plants at Pantai Dalam. Visit www.shimz.co.jp/english/index.html, www.rb.com.my and www.hitachi-pt.comThe route was determined by existing sewer systems and the scheme was devised by Nippon Jogesuido Sekkei (NJS) Consultants. Detailed route and segment design was undertaken by Shimizu designers. Visit www.njs.co.jp Two Kawasaki EPB TBMs drove a total length of 5,365 metres. Both of the TBM operations were carried out concurrently. The alignment is one single length with six shafts (1, 2, 3, 4, 5 and Pantai). The TBMs were launched from shaft 4 and Pantai shaft. TBM 2 drove from Pantai to 5 to 4 (length of 2,430 m, inner diameter 2.8 m). TBM 1 drove from 4 to 3 to 2 to 1 (length of 2,935 m, inner diameter 2.5 m). TBM 1 worked from 9th August, 2004 to 27th October, 2005. TBM 2 worked from 1st September, 2004 to 22nd July, 2005. Each shield is 7 m long (100 m approx. with back-up) and weighs 85 tonnes. TBM 1 had a 3.45 m-diameter cutter head for 3.38 m segments while TBM 2 was 3.75 m in diameter for 3.68 m segments. Visit www.khi.co.jp/index_e.htmlEach ring comprises of four universal segments and one key. The segments were made by SPC Industries in Johor Bahru, Malaysia. They also made jacking pipes for the Pantai sewer network and have made jacking pipes and secondary lining pipes for segment tunnels on the DTSS project in Singapore. Project planners adopted the DTSS idea of lining the segment tunnel with pipes instead of casting in situ HDPE-lined concrete. Mucking-out consisted of a screw conveyor then a conveyor belt into loco/muck train. The earth was hoisted to a surface muck pit by a 30 t gantry. Then excavator/dump trucks at surface.Tunnelling and lining are complete. Shaft 1 is still waiting for a pipejacked connection, shaft 2 and 3 and construction is ongoing at four manholes. Shaft 5 manhole is completed. Pantai shaft has been backfilled. The project is built at an estimated tunnelling cost of USD34.6 million.The EPB shield method involves the application of a suitable pressure to the excavation chamber of the TBM in order to balance with the earth pressure. This is very important to avoid over-excavation around the tunnel. Excavated soil in excavation chambers is discharged by a screw conveyor. One of the critical operations of the EPB method is how smoothly and safely the excavated soil is discharged from the chamber while a suitable pressure is maintained.With reference to the result obtained from soil investigations, the TBMs were expected to encounter UCS with a strength of 30 MP in weathered sandstone. Therefore the cutter heads were designed based on the maximum UCS strength of 30 MP. Based on past experience in similar ground conditions and the known durability of cutter bits, 425 mm-diameter tip-insert double roller cutters were selected as the main cutters. GeologyThe Pantai trunk sewer site is situated on the area with the geological formation known as the Kenny Hill formation, which was formed in the periods of Carboniferous to the Triassic. It consists of sedimentary rock such as mudstone, shale, phyllite and sandstone. These rocks are usually weathered into residual soil of various degrees and various depths. The residual soils are composed of silt, clay, sand and their mixture depends on the degree of weathering and type of origin rock. The Quaternary deposits are usually composed of clay, silt and loose sand with gravel. The tailing material of ex-mining operations is possibly dumped along the tunnel route especially at Pantai Dalam area. Soil conditionerIn this project several types of polymer were used as a soil conditioner and dome-shaped cutter heads with 43.2 cm double roller-utter bits were used for excavation in the Kenny Hill formation. The function of soil conditioner is to increase the quantities of fine particles to create a suitable slurry condition for EPB tunnel operation. Such soil conditioners are required for sand, gravel, sandstone and mudstone profiles. Furthermore, the major advantage of the conditioner is to decrease the friction and adhesion of original soil.Normally, coarse material such as sand and gravel has a relatively large particle size with a large space between the particles. Therefore it has very high permeability. In other words there is no water resistance. Soil conditioner is ideally applied for water resistance and to create low permeability for coarse soil material. A function of soil conditioner is converting the water into fine particles into the void between the particles, thus generating low permeability of sandy mud soil.A high molecular compound (acrylic-resin type) polymer was chosen. This polymer has a high molecular compound and is easily diluted in water. For EPB TBMs, acrylic resin polymer or a mix of acrylic resin and cellulose polymer is normally used. One reason for using the polymer in EPB tunnels is to produce a suitable muddy soil by reducing the friction angle and improving the plasticity and fluidity of the existing soil. SensorsA TBM is equipped with various electronic systems whose function is to display various data and information on the soil profile throughout the excavation. Sensors are installed inside TBMs and various data obtained from the sensors are displayed and analyzed. This data is used to decide excavation parameters. These sensors are very important to manage the TBM excavation, but all depends on various ground conditions and water levels. Therefore information gathered from these sensors is studied to decide the following excavation parameters. Several types of sensors were installed on board the Kawasaki TBMs.The face pressure sensor is the most important sensor for EPB shield machine excavation. The machine applies suitable pressure to the excavation chamber in order to balance the shield pressure against earth pressure, thus avoiding over-excavation.There are various types of geological conditions such as weathered rock, sand, clay and residual soils. The cutter-motor sensor determines proper operation in order to excavate, as well as a guide whether cutter pressure or excavation speed should be increased or reduced. It all depends on this cutter-motor sensor.The excavated soil is conveyed from the chamber to the screw conveyor. To maintain the ideal face pressure, the revolution speed of the screw conveyor and hydraulic oil pressure is adjusted during excavation thanks to a screw conveyor sensor. In addition, the screw conveyor discharge gate opening hydraulic pressure and ratio are also monitored.The TBMs used 12 jacks to push against installed segments to move forward. The condition of the earth being excavated could be judged from the total thrust of these shield jacks monitored by a shield jack sensor. Also, this sensor is the most important part in controlling the direction of the TBM machine. The stroke of the jack influences the excavation length. Thus the excavation speed is controlled by the speed of the jack stroke. For TBM guidance, a gyroscope for horizontal control and a water level system for vertical control were adopted. These two sensors were used in the guidance control system of the TBM. The excavated soil is directly discharged from the screw conveyor. In this process noxious fumes and combustible gases could be mixed in the soil, thus leading to a hazardous environment. To monitor this, a gas detection warning system was installed in the TBMs and the percentage of oxygen and combustible gas in the tunnel was observed continuously.The shaft is a busy and hazardous area, as muck skips and locomotives are in motion either to unload segments or pipes. Control and coordination was exercised at all times so as not to invite any dangerous activity, which could have caused accidents. The shaft top and bottom were observed using a CCTV camera which is set up at the top of the shaft. Visit www.nodig06.im.com.au/pdfs/8%20Alex%20Terry.pdf 13/07.