|Gere HPP Waterway System||References_6445|
The Gere HPP was conceived in previous design phases as a traditional high-head scheme with a nearly horizontal, approx. 2 km long low-pressure headrace and an 800 m long buried penstock. The low-pressure headrace was designed as a tunnel with an exposed pressure line inside, as the tunnel was also intended to be used as access to the headworks during winter.
During the offer preparation for engineering services including tender, detail design, site supervision and commissioning, Lombardi as a member of the JV IGSL proposed a scheme modification with a 2.6 km long inclined tunnel from the powerhouse area up to the desander facilities and the Tirolean intake. The winter access function of the tunnel was maintained as in the original layout. The project was awarded to IGSL adopting this layout optimization.
Drill-and-blast underground excavation is carried out from the d/s portal only. The tunnel portal is located close to the powerhouse, easily accessible and just approx. 300 m from the designated dumping area. After excavation completion, the GRP-line is installed in the tunnel from u/s to d/s. It was possible to optimize and dramatically simplify site logistics compared to the original project layout: the two cableways for conveyance of the excavation material to the dumping area and for penstock installation are no more needed and the project environmental impact are further reduced.
Lombardi has been in charge of all conceptual and design project issues whereas our JV partner is responsible for project management and site supervision.
|Greater Beirut Water Supply Project - General Planning||References_2000|
The project consists in the construction of a 24 km long headrace tunnel and 10 km of adduction pipes in order to exploit the Litani and Awali rivers for domestic use. The water is drawn from a hydro power plant, located in Joun at about 30 km apart from South Beirut, and conveyed to the Hadath and Hazmieh tanks, under design on the city uplands.
The water supply system is calculated to support future growing flow rates starting from 3 up to 9 m³/s and includes:
- 3 tunnels of about 24 km length and 2.8 m of diameter, excavated by 2
TBMs, and with a double ring of shotcrete and concrete coated with inserted
PVC waterproof membrane;
- 2 ventilation shafts, near the Damour syphon and a piezometric tank at the
North portal of Khalde;
- 1 syphon, which leads to a difference of 140 m in elevation and allows the
underground crossing of the Damour river. The connecting branches are
excavated into the rocks with conventional method and crossing in open air in
the fluvial deposits;
- 2 buried pipes, 10 km long and 1’400 mm of diameter each, both designed for
pressures up to 25 bar;
- 1 SCADA system for the plant control, which commands the numerous valves
of controlling and interception.
The watertight tunnel is designed taking into account low overburden and high pressure.
|Alto Piura Water Transfer||References_6453|
The Alto Piura Project is located in the north of Peru in the Piura Region, provinces of Huancabamba and Morropón, both on the east of Piura City. The aim of the project is to transfer water from the Huancabamba river situated on the east of the Peruvian Andes to the Pacific basin by means of a tunnel crossing through the Andes.
The Project includes various hydraulic infrastructure works and will have a significant impact on the economy of the region, as the water will serve to irrigate 50’000 ha of farmland providing 335 M cubic meters of water per year. In this way, the total area of irrigated land will increase by about 19’000 ha, which will contribute to expand the current agricultural exports of the region.
The main components of the Project are the Tronera Sur Dam, the Transfer Tunnel and the Access Roads.
The works at the Tronera Sur Dam comprise mainly a gated barrage with four radial gates (5.35 m high and 7.60 m wide) and a smaller radial gate (5.35 m high and 3.00 m wide). Additionally, there is a desander structure with 3 basins, each of them sub-divided into two smaller basins. The structure of the desander is approximately 51 m long and 44.8 m wide.
The stilling basin of the spillway is 38.5 m long and 41.4 m wide. The desander is equipped with a gated flushing system and an intake structure which is located in the channel of the Huancabamba river. The design flow is 26.4 m3/s which will be transferred by the 12.7 km long tunnel with a hydraulic section of 15.65 m2.
|Rehabilitation of Cassarate Penstock||References_6444|
AEM (Azienda Elettrica di Massagno SA) operates the hydropower plant Cassarate which exploits the flow of the rivers Cassarate and Franscinone in Canton Ticino (CH). The plant comprises a headrace tunnel at an elevation of 598 m. a.s.l. (maximum headpond water level) and a powerhouse at an elevation of 346 m. a.s.l. located in the Lugano suburbs. The hydropower plant has a gross head of 252 m and an installed capacity of 3.8 MW. The total length of the buried penstock, built in the year 1975, is about 1’520 m with a diameter of 1’000 mm.
The rehabilitation works consist in the renewal of the internal corrosion protection coating of the steel penstock and the decommissioning of the existing headpond, by means of directly connecting the headrace tunnel to the penstock.
The work phases of the renewal of the steel pipe are the following:
- Preparation of temporary openings in the penstock, cutting the pipe for a
length of 4 m in three points at equal distance, given that the diameter of the
existing manholes is not suitable for a good access into the pipe (450 mm);
- Removal of the existing internal protective coating byHDW (high pressure
water jetting) and sand blasting;
- Expansive cleaning and restoration of the existing corrosion pits inside the
pipe, by means of surface refining (grinding);
- Application of the new protective coating in 4 layers for a total thickness of
The existing Sonvico headpond will be decommissioned and bypassed by a PRFV pipe with a diameter of 1100 mm linking the headrace tunnel directly to the penstock. In fact, the headrace tunnel has a compensation volume of 16'000 m3, higher than that of the decommissioned basin, and the gross head of the HPP is slightly increased in the new configuration.
|Resses embankment - Villargondran (73)||References_6919|
|ENEL - Linee guida gallerie con TBM||References_5505|
In the last 60 years the excavation methods varied greatly, mechanized tunneling bringing significant progress to the safety and quality of the final product and the execution rate. The design approach extends more than the evaluation of the overall rock or soil conditions and characteristics, the subsequent convergence-confinement behavior or rock wedges (deep tunnels) and chimney-silo-caving risks and relevant loads (shallow tunnels). The risks involved by mechanized excavation become more visible with the time passing, for more complex and difficult conditions are often to be crossed by the more recent projects. The selection of the suitable method is a challenge for the designer, confronted not only with the geological, hydrogeological and geotechnical aspects for selecting the suitable countermeasures but adjusting the work progress to the variations of the local conditions. By mechanized methods, these adjustments can be only limited. Therefore the design good for construction should represent the suitable balance between an economical construction approach and the need for assuring the successful crossing of all the conditions foreseen to be encountered, in their worst expression. The thoroughly analysis of the known conditions is then to be supported by a risk analysis focused to the critical verification of "what/if" situations in order to assess the completeness of the design and to determine if and at how contingency measures and residual risks are to be considered for the construction and for financial or insurance allocations. In all this, collateral aspects such as the logistics (accesses, supply lines/times and possible emplacement of the support installations) and the human factors (experience of the contractor and general construction culture at the project location) become significant aspects, possible to be killer factors for a solution by mechanized tunneling.
The task is the formulation of a guideline through this process, for allowing the selection of the most suitable excavation method or methods in a given project layout and conditions.
|Greater Beirut Water Supply Project - Transient Analysis||References_6485|
The project includes the construction of a 20 km long headrace tunnel and 10 km of adduction pipes in order to exploit water of the Litani and Awali rivers for domestic use. The water is drawn from a hydro power plant, located in Joun at about 30 km apart from South Beirut, and conveyed to the Hadath and Hazmieh tanks, under design on the city uplands.
The scope of the work was to analyze the overall transient response of the hydraulic system, which includes mass oscillation and waterhammer phenomena. Calculations were made with the software PIPE 2016 Surge for the transient analysis.
The following scenarios have been investigated:
- Control operation (Gradual start up and gradual shut down);
- Emergency cases (burst scenario in different configurations);
- Extreme events (shut down at the same time of the Flow Control valves
FCV) in the final reservoirs and total close of the Flow Isolation Valves (FIV)
in case of fault in the Distribution Chambers stretch).
The transient analysis for the Tender Design lead to the conclusion that the design of the hydraulic system needs to be adapted and optimized in order to ensure acceptable responses for all critical transient scenarios.
The solutions proposed consisted of:
- Change the detection system of fault;
- Split the system in the adduction pipes (independence of the two pipes);
- Increase the dimension of OIP (Ouardaniye Inlet Portal);
- Install feeder tanks in KOP (one for each pipe);
- Install air valves downstream of the FIVs in KOP and upstream of the check
valves and BV located at HCC (Hazmieh Connection Chamber).
|Sihl Flood Relief Tunnel, Owner's engineering SIA phases 32-33||References_7006|