Numerical Analysis of a Deep Excavation in Front of MarmorKirken, Copenhagen

In this paper, the main results of a numerical geotechnical analysis of the deep excavation carried out in front of MarmorKirken in Copenhagen are presented and compared with the observed performance. The excavation has a maximum depth of about 35 m; a full top-down construction technique was adopted in order to minimize the effects induced by the excavation works on the monument. Foundation soils are characterized by the presence, starting from a depth of about 13 m, of a limestone formation. The comparison between predicted and observed performance shows that a significant amount (about 50%) of the maximum settlements experienced by the church occurred during the construction stage of the retaining wall panels in front of the church. Numerical analyses got the order of magnitude of displacements, but underpredicted both panel construction and excavation induced settlements of the church, while a better agreement was found for horizontal displacements

Exploitation of drainage water heat: A novel solution experimented at the Brenner Base Tunnel

Deep tunnels in permeable fractured rock-masses and under high piezometric levels can drain notable volumes of warm water, which are collected under gravity in specific conduits towards the portals, where heat can be exploited. The utilization of this energy source is generally narrowed by the limited presence of end-users near the portals, while other promising heating and cooling needs can be found directly along the tunnel length. The work presents the design, construction and installation of a geothermal system prototype exploiting the drainage water heat directly inside the tunnel. The prototype was named Smart Flowing due to the peculiarity of its heat exchange process. The system was realized and installed inside the exploratory tunnel of the Brenner Base Tunnel, near the border between Italy and Austria. The Smart Flowing modules were built outside and later moved inside the tunnel, where they were placed and assembled concurrently to the advancement of the Tunnel Boring Machine. A design procedure was proposed and validated against a testing and monitoring campaign. The data from the experimental activity confirmed that the drainage water flow guarantees long-term stabilization of circulating water temperature and fast heat recovery afterwards, thus securing the considerable power and performance values of a water-water heat pump connected to the system. A sensitivity analysis allowed the reproduction of different working scenarios, in order to generalize the application of Smart Flowing beyond the specific installation context

A new in situ test for the assessment of the rock-burst alarm threshold during tunnelling

Rock-burst is one of the most serious risks associated with hard rock tunnelling and mining at high depths. Monitoring of acoustic emissions emitted by the rock-mass during excavation and their interpretation now permits the early assessment of failure events and makes the safe management of the construction works possible. A reliable set-up of the alarm threshold is thus fundamental for the correct implementation of the procedures planned to minimise rock-burst related risk. This paper focuses on a novel in situ test specifically developed to provide an experimental basis for a more accurate assessment of the alarm threshold during tunnelling, representative of the local geomechanical conditions. The test, thanks to the compression induced by two flat jacks at the tunnel side wall, produces an artificial failure process during which acoustic emissions are measured and correlated to the mechanical response of the rock-mass, without the typical limitations of scale that characterised the laboratory experiments. The new methodology, named the Mules method, was successfully tested during the excavation of some stretches of the Brenner Base Tunnel in the Brixner granite, affected by mild spalling episodes. The case-history is fully described in the paper to illustrate the practical application of the proposed approach

Class A predictions of damage level in an historical fortress induced by twin tunnelling

Tunnelling below historical city centres requires the accurate analysis of the impact of construction works on cultural heritage monuments, which need to be preserved from any possible damage. In this paper, the undercrossing of an historical masonry structure in the city of Florence (Italy), the Fortezza da Basso, by two tunnels of the new high-speed railway underground line is analysed. The interaction problem is studied by a 3D class-A finite element numerical model. Advanced constitutive laws are adopted to describe the key features of the mechanical behaviour of both soil layers and masonry structures. The results of the analyses show that the excavation process is likely to induce a negligible to slight damage in the historical fortress when a typical surface volume loss of 0.5% is considered in greenfield conditions

3D modelling of soil-rock mixtures considering the morphology and fracture characteristics of breakable blocks

Failure mechanisms of a soil-rock mixture (S-RM) can be efficiently investigated by the discrete element method (DEM). This paper proposes a stochastic approach for 3D DEM modelling of S-RM samples accounting for morphological features and internal fractures of blocks and their potential breakage. The research refers to the case-history of an artificial S-RM filling slope, mainly containing highly-weathered shale blocks, constructed at the ±500 kV electronic converter station in the Funing County, Yunnan Province, China. The 3D morphological features of the blocks and the characteristics of their internal fractures were obtained by CT technology and image processing. A stochastic method based on harmonic series was developed starting from the real blocks, allowing the generation of random block clusters with characteristics similar to the original ones. Another stochastic approach was implemented for the creation of the internal fractures, simulated as voids in the block clusters, following the characteristic of the real fractures. Finally, the procedure was applied for the definition of a 3D S-RM DEM model with 40% block proportion, whose meso-parameters were determined for simulating direct shear tests. These latters were also useful to explore the mechanical response of the sample at the mesoscale, including the formation and development of the localization band. The numerical results showed that the generated random S-RM DEM model well reproduced the experimental behaviour of S-RM samples with breakable blocks. Also, they highlighted the importance of modelling the block breakage and internal fractures; in fact, companion simulations with unbreakable blocks and breakable blocks without fractures were all characterised by increased shear strength with higher friction angle but reduced cohesion

レーザー ニ ヨル カクユウゴウエネルギー ノ カイハツ

研究ノー

Tunnel–framed building interaction: comparison between raft and separate footing foundations

This paper investigates the influence of the foundation configuration (raft or separate footings) on tunnel-soil-framed building interaction using geotechnical centrifuge testing. Tunnelling-induced soil movements and deformation fields, framed building displacements, and structure shear distortions (with associated modification factors) are illustrated. Framed building stiffness and footing bearing capacity are also evaluated experimentally. Results show that the foundation configuration plays an important role in determining the ground response to tunnelling, affecting soil displacement fields as well as the distribution of soil shear and volumetric strains. In particular, foundation settlements and differential horizontal displacements are larger for separate footings compared to raft foundations. The effects of building width, weight, and eccentricity (with respect to the tunnel) on foundation settlements and structural distortions is quantified for separate footings and contrasted against results for raft foundations. The modification factor of the maximum building shear distortion is linked to the relative soil-building shear stiffness; interestingly, for buildings with similar values of relative stiffness, the level of shear distortion within framed buildings is lower for separate footings than rafts

Tunneling-Induced Deformation of Bare Frame Structures on Sand: Numerical Study of Building Deformations

The paper compares the performance of two Finite Element Method approaches in reproducing the response of bare frame structures to tunneling in dry dense sand. A fully coupled approach, in which the tunnel, frame and soil are accounted for, is compared with a two-stage method incorporating simpler structural and soil models. The two approaches are validated against centrifuge test results of tunneling in sand beneath frames founded on either rafts or separate footings. Both approaches provide good estimates of displacements and distortions experienced by the frames provided that the soil-foundation interface and structural stiffness are correctly accounted for. The numerical models are also employed to extend the range of eccentric configurations investigated with centrifuge tests. The results demonstrate that shear deformations play an important role for all considered buildings, whereas only frames on separate footings are sensitive to horizontal ground movements. Finally, data are synthesized using modification factors and recently proposed relative stiffness terms

Holmium laser enucleation of the prostate with Virtual Basket mode: faster and better control on bleeding

Background: To compare clinical intra and early postoperative outcomes between conventional Holmium laser enucleation of the prostate (HoLEP) and Holmium laser enucleation of the prostate using the Virtual Basket tool (VB-HoLEP) to treat benign prostatic hyperplasia (BPH). Methods: This prospective randomized study enrolled consecutive patients with BPH, who were assigned to undergo either HoLEP (n = 100), or VB-HoLEP (n = 100). All patients were evaluated preoperatively and postoperatively, with particular attention to catheterization time, operative time, blood loss, irrigation volume and hospital stay. We also evaluated the patients at 3 and 6 months after surgery and assessed maximum flow rate (Qmax), postvoid residual urine volume (PVR), the International Prostate Symptom Score (IPSS) and the Quality of Life score (QOLS). Results: No significant differences in preoperative parameters between patients in each study arm were found. Compared to HoLEP, VB-HoLEP resulted in less hemoglobin decrease (2.54 vs. 1.12 g/dl, P = 0.03) and reduced operative time (57.33 ± 29.71 vs. 42.99 ± 18.51 min, P = 0.04). HoLEP and VB-HoLEP detrmined similar catheterization time (2.2 vs. 1.9 days, P = 0.45), irrigation volume (33.3 vs. 31.7 l, P = 0.69), and hospital stay (2.8 vs. 2.7 days, P = 0.21). During the 6-month follow-up no significant differences in IPSS, Qmax, PVR, and QOLS were demonstrated. Conclusions: HoLEP and VB-HoLEP are both efficient and safe procedures for relieving lower urinary tract symptoms. VB-HoLEP was statistically superior to HoLEP in blood loss and operative time. However, procedures did not differ significantly in catheterization time, hospital stay, and irrigation volume. No significant differences were demonstrated in QOLS, IPSS, Qmax and PVR throughout the 6-month follow-up. Trial Registration: Current Controlled Trials ISRCTN72879639; date of registration: June 25th, 2015. Retrospectively registred

Performance of the CMS Cathode Strip Chambers with Cosmic Rays

The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 microns to 243 microns. The efficiencies for local charged track triggers, for hit and for segments reconstruction were measured, and are above 99%. The timing resolution per layer is approximately 5 ns