Multi layered shotcrete design for tunnel construction

Shotcrete linings have been applied successfully for a large number of tunnel constructions within the last couple of decades all around the world. While up to the 1980’s the structural design of the shotcrete linings mainly was based on experience gathered throughout the construction and some simplified analyses in the following years the application of the Finite Element Method lead to much more sophisticated design and more accurate estimation of deformations and stress state in the shotcrete lining. This was amongst others achieved by considering the time and construction sequence - dependent development of the deformations as well as by applying simplified time dependent material laws for shotcrete. The design verification as such is commonly done by using the methods as stated in Eurocode 2 for ULS and SLS. The design becomes even more complex for cases in which during a first construction stage one shotcrete layer is applied and stressed and only later additional, stress free layers are applied in order to carry additional loads caused by further construction stages. With such situations tunnel designers have to deal frequently in cases when cross sections between two main tunnels need to be installed or a second, parallel tunnel is driven while the first tunnel is already in place. Within this paper the special case of such multi – layer shotcrete linings is discussed and proposals for the calculation of the stress state in the lining and the design verification are made

Untersammelsdorf Tunnel – Challenges, Special Measures and use of Special Shotcrete for Tunneling in Lacustrine Clay

The 665 m long, twin-track Untersammelsdorf Tunnel is being built in the course of the construction of the Koralmbahn line between Graz and Klagenfurt. The tunnel is located in extremely challenging subsoil conditions consisting of silty to fine sandy lacustrine deposits. The developed tunneling concept provided wide-ranging special underground engineering measures as piling, jet grouting and temporary struts and represents a unique construction method to date. Accordingly, numerous challenges arose in the design phase, which could be verified by carrying out extensive trials and investigations in the preparatory period or for which fallback levels had to be provided for the support system. Please click Additional Files below to see the full abstract

Burden of hospital admissions and resulting patient interhospital transports during the 2020/2021 SARS-CoV-2 pandemic in Saxony, Germany

Abstract Secondary transports of patients from one hospital to another are indicated for medical reasons or to address local constraints in capacity. In particular, interhospital transports of critically ill infectious patients present a logistical challenge and can be key in the effective management of pandemic situations. The state of Saxony in Germany has two characteristics that allow for an extensive evaluation of secondary transports in the pandemic year 2020/2021. First, all secondary transports are centrally coordinated by a single institution. Second, Saxony had the highest SARS-CoV-2 infection rates and the highest COVID-19 associated mortality in Germany. This study evaluates secondary interhospital transports from March 2019 to February 2021 in Saxony with a detailed analysis of transport behaviour during the pandemic phase March 2020 to February 2021. Our analysis includes secondary transports of SARS-CoV-2 patients and compares them to secondary transports of non-infectious patients. In addition, our data show differences in demographics, SARS-CoV-2- incidences, ICU occupancy of COVID-19 patients, and COVID-19 associated mortality in all three regional health clusters in Saxony. In total, 12,282 secondary transports were analysed between March 1st, 2020 and February 28th, 2021, of which 632 were associated with SARS-CoV-2 (5.1%) The total number of secondary transports changed slightly during the study period March 2020 to February 2021. Transport capacities for non-infectious patients were reduced due to in-hospital and out-of-hospital measures and could be used for transport of SARS-CoV-2 patients. Infectious transfers lasted longer despite shorter distance, occurred more frequently on weekends and transported patients were older. Primary transport vehicles were emergency ambulances, transport ambulances and intensive care transport vehicles. Data analysis based on hospital structures showed that secondary transports in correlation to weekly case numbers depend on the hospital type. Maximum care hospitals and specialized hospitals show a maximum of infectious transports approximately 4 weeks after the highest incidences. In contrast, standard care hospitals transfer their patients at the time of highest SARS-CoV-2 case numbers. Two incidence peaks were accompanied by two peaks of increased secondary transport. Our findings show that interhospital transfers of SARS-CoV-2 and non-SARS-CoV-2 patients differ and that different hospital care levels initiated secondary transports at different times during the pandemic