Special foundations

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Vedeggio-Cassarate Road Tunnel - Section in Loose MaterialReferences_3716
The Vedeggio-Cassarate tunnel (L = about 2'630 m) connects the Vedeggio valley in the west with the Cassarate valley in the east, near the city of Lugano, Switzerland. The tunnel is flanked by a safety tunnel at a distance (interaxis) of 30 m along its entire length. In the first 200 m from the Cassarate portal, the tunnel crosses extremely heterogenous quaternary deposits consisting of fine sands with silt, sandy and clayey silts, from medium to strongly consolidated and generally not very permeable. The paleochannels of the Cassarate river are interspersed in these soils, filled with coarser fluvial deposits with higher permeability which appear as layers or lenses in which pressurized aquifers (artesian groundwaters) with water levels reaching up to 20.0 m above ground level can be found. On the surface there are some residential buildings and the high school of Canobbio. For the excavation, the ground was pre-consolidated both from the surface in the initial section (10 m for the safety tunnel, 30 m for the main tunnel) with a low covering, and starting from the heading face on the next section up to the contact with the rock. The consolidation from the surface was achieved by using by-fluid jet-grouting forming vertical secant columns. The underground consolidation for both tunnels was performed in dvance of the excavation front with single-fluid jet grouting at the boundary of the excavation and in the excavation face. The jet-grouting columns are 15.0 m long and have an overlap of 5.0 m. Due to the presence of several residential buildings and the Cantonal High School on the surface, an intensive measuring system (total station, extensometer, piezometer, etc.) with automatic data supply is set up. Part of this is the measurement- and intervention concept, which defines the structure and responsibilities of the monitoring team as well as intervention measures for the different alert levels.
Pianturino Viaduct - Stability Analysis of Anchored StructuresReferences_8743
The Pianturino Viaduct is located along the N02 road, near the Cadenazzo Municipality. It was built between 1978 and 1980. It is a reinforced concrete structure with 3 spans (55-70-55 m) crossing the valley of the same name at about 70 m above the valley bottom. The project provided for the use of permanent pre-stressed anchors to ensure the stability of the protection walls of the pier foundations and the retaining structures of the abutment on the Chiasso side. In 1992, the anchored structures were subjected to extraordinary maintenance consisting in the integration of new anchors. Following the general inspection in 2019, FEDRO commissioned Lombardi SA to conduct a study with the aim of quantifying to what extent the stability of the slopes and anchored structures depend on the current state of preservation of the anchors. The methodological approach adopted was based on the logical sequence foreseen by SIA 269 and on the procedural approach of FEDRO Directive 12005. The updating information phase included the general examination of the structures, definition of the conservation state of the anchors and updating the geological-geotechnical reference model. The updated geotechnical and structural verifications of the anchoring elements showed that, with reference to the safety levels required by the regulations in force and the residual service life of the viaduct, the stability of the slopes and the structural safety of the works depend on the contribution of the prestressed anchors. Given the impossibility of establishing the ultimate anchor strength, linked to the evolution of the degradation processes of the system (reinforcement and header), retrofitting of the anchored structures was proposed in relation to two types of approaches: preservation of the existing and replacement of the anchors, respectively. Different investment scenarios related to the remaining service life were provided to the client.
Stöckalp - Melchsee-Frutt, Rehabilitation of the foundation of the penstockReferences_790
The power plant Hugschendi is located close to Stöckalp (Melchtal) and was put into operation in 1957. Two Pelton turbines with an output power of 7 MW each were installed. Water from the catchment area Melchsee-Frutt, which is stored in the Lake Tannen and Lake Melch, is released through the turbines. The gross head is around 830 m. Since the completion of the plant, the 3’385 m long penstock (Ø=0.7-0.9 m) leading from Melchsee-Frutt to the Stöckalp has been permanently in operation. At every horizontal or vertical bend of the open line, there is a fix-point. Downstream of these fix-points there is always an expansion joint, with which the longitudinal expansions can be accommodated. Between the fix-points, the penstock is held in regular intervals. On behalf of the operator Obwalden EWO, the condition of all 80 existing penstock plain bearings were registered. Depending on the assessed good to defective status of the structure, a prioritization of certain foundations and a corresponding graded schedule planning for the rehabilitation works were proposed. Based on the status report, in further commissions for the EWO, a measure planning for all foundations as well as the final design, submission and realization of a pilot project for the entire replacement of the foundations have been elaborated.
ATG - Gotthard Base Tunnel - Settlement calculations cut-and-cover section BodioReferences_313
The Bodio Portal at the southern end of the 57 km long Gotthard Base Railway Tunnel consists of a cut and cover section with two tubes of approx. 380 m length. Both cut and cover tunnels connect the actual portal with the underground section, advancing through a section with heterogeneous blocky soil. Based on the local geology and geological history, no time depending settlements were expected at the beginning of construction. However, after initial settlements a continuation at a constant low rate, showing almost no changes for years, was observed. As consequence, further ground investigations with deep core drillings up to a depth of approx. 200 m were carried out. Lombardi Ltd. was charged with the interpretation of the results of these additional ground investigations as well as the analysis of possible mechanism including the prediction of the future development of these settlements. Two mechanisms or the combination of both of them could be identified as possible cause for the still ongoing ground deformation. One possibility is that the settlements are caused by an ongoing consolidation of the deep lacustrine deposits (between 100 m and 160 m beneath the tunnel. The ongoing deformation could, however, also be referred to creep phenomena within the cohesive formations.
Hausmatt Tunnel - Cut and Cover Section WestReferences_806
The construction of the 4.5 km long bypass between the roundabout Säli and the connection to the Mittelgäustrasse close to Rickenbach presents an important step to solve the regional traffic congestion in the region of Olten. The 45 m long cut and cover section is directly followed by the bored tunnel section and underpasses two existing industrial tracks. For the planned works, the tracks can be put out of service for only short time periods. Therefore, and because of the geometry of the track system, the cut and cover section was constructed using the top-down method, whereupon the excavation underneath the cover was performed. The cut and cover profile is designed as a rigid closed frame structure; it is partly located 3 m below the groundwater level, so that it had to be designed as a waterproof concrete structure.
Vedeggio-Cassarate Road Tunnel - Civil worksReferences_109
The Tunnel Vedeggio-Cassarate (L=ca.2'630 m) links the Valley of the Vedeggio River to the Valley of the Cassarate River northern of the city of Lugano in Switzerland. The project is a single bidirectional tunnel. The cross section has an intermediate slab, which separates the traffic space from the exhaust air aspiration channel. A parallel safety tunnel (Ø 4.5 m) was excavated on the south side of the main tunnel (30 m). Every 300 m, there are bypasses alternately for pedestrians and vehicles linking both tunnels. The first 2’350 m from the portal Vedeggio were excavated by D&B through the crystalline rock of the south alpine formations. The following ca. 200 m up to the portal Cassarate were excavated in loose material composed of quaternary heterogeneous glacial-river deposits in different consolidation states, with several independent artesian water tables characterized by pressures up to 2 bars.In the loose ground stretch the ground had to be previously consolidated with jet grouting. Where this was not possible from the surface the ground was consolidated in advance of the tunnel face with jet grouting and fore polling. In the middle of the tunnel is located a cavern equipped with two ventilators for the aspiration of the fume in case of fire and electromechanical devices serving the whole tunnel. The exhausted air is then expelled through a 60 m long tunnel and a 100 m high vertical shaft to the surface. The tunnel crosses twice the new Ceneri Base tunnel of the Gotthard main railway line with only few meters overburden (5 m and nearly 2 m).
Galgenbuck Tunnel - Preliminary Cut EngiReferences_910
The portal pit Engi is prerequisite for the construction of the Galgenbuck Tunnel . The portal is located on the weste of the Tunnel and represents the access for all excavation works. After the conclusion of the excavation works, a cut & cover tunnel will be built in this same pit, shaping the ground with its original form. The portal pit Engi is approximately 80 m long and 75 m wide. The maximum excavated height is approx. 22 m. The support walls are formed by separated or tangential bored piles Ø 80 and Ø 100 cm. The pile walls are supported with several layers of pre-stressed tendons whose forces are distributed by means of a longitudinal steel bracing. Due to the 6 year long duration of the works, the tendons had to be designed and executed as permanent tendons, i.e. with a full corrosion protection. Construction methods: Wall of separated piles with shotcrete reinforcement; Walls of tangential piles; Tendons with longitudinal steel bracing. Characteristic values: Total length excavated piles (Ø 800 and Ø1‘000 mm): 2‘350 m; Reinforcement of the piles: 99 to.; Pre-stressed tendons: 11‘000 m; Longitudinal steel bars: 77 to.; Passive anchors and nails: 540 m; Excavated material (rock and loose material): 44‘000 m³
Cityring Lucerne - Foundation EngineeringReferences_918
The A2 motorway around Lucerne on the Basle–Chiasso axis is one of the busiest road stretches in Switzerland. The Emmen-Lucerne-Kriens section is characterized by a number of 1970's-era engineering structures: the Lehnen viaduct along the Reuss in the north, the roughly 600-metre-long Reussport tunnel, the Senti bridges over the Reuss linking to the city as well as the 1.5-kilometre-long Sonnenberg tunnel to the south. After almost 40 years of operation, steadily increasing traffic has left its marks. Between 2009 and 2013 the total renovation project of the Lucerne Cityring includes the upgrade of the roads and tunnels to a technology and safety level according to today’s standard. To maintain the flow of commuter traffic during the day and at the peak travel periods, the total renovation was done during night and on selected weekends. The construction demanded a lot from contractors, planners and builders, authorities, commercial enterprises as well as the residential population around Lucerne. Joining forces allowed to meet the challenges of this highly ambitious project. Thanks to the tremendous efforts of the building professionals, the extensive transport and structural measures as well as intensive outreach, the job was completed in time and at tolerable impact for the Lucerne region.
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