Mud pumping in the roadbed of ballastless high-speed railway

International audienceMud pumping that is deliberately avoided in the design of a ballastless high-speed railway still occurs and induces extraordinary track vibrations. In this study, in situ investigations and laboratory tests were performed to disclose the initiation and development of mud pumping detected in the field. The in situ investigations indicated that mud pumping principally appeared at both ends of the concrete base up to a maximum distance of 2 m. Precipitation, instead of groundwater, was found to be the water source triggering mud pumping; this infiltrated the graded gravel roadbed through the detachments of the ends of the overlying concrete bases due to the whipping effect. Once mud pumping occurred, the vibrations of concrete bases were aggravated and caused severe track settlements under train loads. The results of laboratory tests indicated that the infiltrated rainwater was retained in the roadbed above the less permeable subgrade, and the roadbed contained an unstable particle skeleton with excessive plastic fine particles, both of which provided favourable conditions to form mud pumping under dense high-speed train loads. Soil particles of less than 7·1 mm in diameter migrated during mud pumping; these first accumulated at the lower roadbed, then gradually migrated to the upper roadbed, actuated by the hydraulic gradient generated, and were finally pumped out through the detachments around the expansion gaps, thereby resulting in large amounts of voids in the roadbed and a vicious cycle if not treated in a timely fashion. These features of mud pumping in ballastless tracks differ from those of ballasted tracks and will benefit the development of remediation measures and improvement of slab track designs

Remediation of mud pumping in ballastless high-speed railway using polyurethane chemical injection

International audienceMud pumping induced by repeated train passages is one of the most serious distresses not only for ballasted tracks but also for ballastless tracks. In this study both field and laboratory tests were performed to find out the main influencing factors and to further develop a new remediation method. Field observations showed that mud pumping in ballastless track mostly occurred at both ends of concrete base (the expansion joints), triggered mainly by the whipping effect of track vibration due to repeated train passages. Based on the results from cyclic uniaxial test on polyurethane-aggregate specimen, showing an excellent resilience behavior and a high and stable quasi-static elastic modulus under the stress amplitude of 80 kPa for 3 million cycles, a remediation method with Polyurethane Chemical Injection (PCI) was developed for mud pumping in ballastless track, which consisted in injecting polyurethane chemical materials into roadbed at an angle of 45° to get a large stabilized area. Field testing and monitoring showed that after PCI remediation, the vibration acceleration decreased by 16.7% at the end of track slab and by 9.1% in the middle of track slab in 12 h; the deviator of the vertical track alignment was reduced from −9.58 mm to −0.08 mm in 3 days. A longer 6-month filed monitoring showed that the vertical track alignment deviator remained in a relatively low level (less than −0.62 mm) after PCI remediation, and there was no mud pumping reoccurrence in the PCI remediated area, indicating the performance of the proposed remediation method

A new record and a novel morph description of Boiga stoliczkae (Squamata, Colubridae) from China

The Asian Cat Snake genus Boiga Fitzinger, 1826 includes 37 species, with high species diversity. Five species of Boiga have been recorded in China including B. multomaculata (Boie, 1827), B. kraepelini (Stejneger, 1902), B. cyanea (Duméril, Bibron & Duméril, 1854), B. guangxiensis (Wen, 1998) and B. siamensis (Nutaphand, 1971). Previously, the validity of the species Boiga stoliczkae (Wall, 1909) was controversial. B. stoliczkae was considered in synonymy with B. ochracea. Currently, the taxonomy of B. multomaculata and B. ochracea (Theobald, 1868) was revised so that B. multomaculata and B. ochracea actually represent a single species and B. stoliczkae was recognised as a valid species. B. stoliczkae was previously known to be found in the west from central Nepal through Darjeeling, Sikkim and Bhutan to Arunachal Pradesh and Assam in north-eastern India.One adult female specimen of the Asian Cat Snake was collected from Gyirong County, near the China-Nepal border, Tibet, China during fieldwork on August 2023. We compared morphology and mitochondrial DNA sequence data with all the species of the genus Boiga. Both datasets strongly supported referring the Chinese specimens to B. stoliczkae (Wall, 1909) due to the 21 mid-dorsal scale rows and the uncorrected p-distance (mitochondrial DNA gene cytochrome b) between this specimen and B. stoliczkae which is 1.7%. We further described morphological characters of the Chinese specimen in detail and compared these with the specimens that had been previously described. The dorsal ground colour of the Chinese specimen is dark brown, with a black stripe distributed almost evenly across the tail. This is a novel morph of the species B. stoliczkae. The newly-collected Chinese specimen expands the distribution of the species on the Himalaya range

Metal mixture and osteoporosis risk: Insights from plasma metabolite profiling

The pathophysiology of osteoporosis (OP) is influenced by exposure to nonessential harmful metals and insufficient or excessive intake of necessary metals. Investigating multiple plasma metals, metabolites, and OP risk among older adults may reveal novel clues of underlying mechanisms for metal toxicity on bone mass. A total of 294 adults ≥ 55 years from Wuhan communities were included. Plasma concentrations of 23 metals and metabolites were measured via inductively coupled plasma-mass spectrometry and global metabolite detection. To investigate the relationships between plasma metals, OP risk, and OP-related metabolites, three different statistical techniques were used: generalized linear regression model, two-way orthogonal partial least-squares analysis (O2PLS), and weighted quantile sum (WQS). The mean ages were 66.82 and 66.21 years in OP (n = 115) and non-OP (n = 179) groups, respectively. Of all 2999 metabolites detected, 111 differential between-group members were observed. The OP risk decreased by 58.5% (OR=0.415, 95% CI: 0.237, 0.727) per quartile increment in the WQS index indicative of metal mixture exposure. Consistency remained for bone mineral density (BMD) measurements. The O2PLS model identified the top five OP-related metabolites, namely, DG(18:2_22:6), 3-phenoxybenzoic acid, TG(16:1_16:1_22:6), TG(16:0_16:0_20:4), and TG(14:1_18:2_18:3), contributing most to the joint covariation between the metal mixture and metabolites. Significant correlations between each of them and the metal mixture were found using WQS regression. Furthermore, the five metabolites mediated the associations of the metal mixtures, BMD, and OP risk. Our findings shed additional light on the mediation functions of plasma metabolites in the connection between multiple metal co-exposure and OP pathogenesis and offer new insights into the probable mechanisms underpinning the bone effects of the metal mixture