Model tests on subsurface cavities below road pavement due to sand eruption from the liquefied ground

A significant number of subsurface cavities was found in the liquefied ground after the 2011 Great East Japan earthquake. Using the results of the radar exploration conducted along the coastal area of Tokyo Bay, characteristics of subsurface cavities were investigated. The size and shape of the cavities are larger and thinner compared to those of cavities observed in the non-liquefied ground. A series of model tests was conducted in order to understand the mechanism of sand eruption and underground cavity formation when liquefaction occurs. It was found that the flow rate at the opening seems to be the most important factor for the sand eruption

Exploring the micro-to-macro response of granular soils with real particle shapes via \u1d741\u1d46a\u1d47b-aided DEM analyses

This contribution provides high fidelity images of real granular materials with the aid of X-ray micro computed tomography (μCT ), and employs a multi-sphere approximation to reconstruct non-spherical particles. Through the discrete element method (DEM) simulations on granular samples composed of these non-spherical clumps, the effect of particle shape on the macroscopic mechanical response and microscopic soil fabric evolution is examined for sheared soil assemblies under triaxial loading conditions. Simulation results indicate that materials with more irregular particles tend to show higher shear resistance in both peak and critical stresses, while more sphere-like materials tend to exhibit lower void ratio and mean coordination number values under isotropic loading conditions and in the critical state. The proposed critical state parameters for describing the sensitivity of the mean coordination number to confining pressures are larger as particles become more irregular. At a microscopic level of observation, more irregular materials appear to exhibit higher fabric anisotropy in terms of contact normal and particle orientation in the critical state. The critical stress ratio determined through experimental and simulation results are found to be linearly linked to the shape-weighted fabric anisotropy index

Variation of small strain stiffness for piping-influenced Toyoura sand

Landslides triggered by piping are frequently reported during stormy periods. Despite large amount of model tests related with internal erosion, there is little research on the mechanical properties of disturbed soil by means of element experiment. In this paper, an attempt was made to create artificial piping by dissolving water soluble material (glucose) in sand. Chains of voids were generated when water was infiltrated and drained out through the specimen. Small torsional cyclic loadings were conducted on the hollow cylindrical specimens in order to obtain the small strain stiffness of the soil before/after piping erosion. According to the results, reduction of shear modulus was found in specimen with internal pipes after water infiltration, and piping-induced anisotropy was found to be obvious

p53 expression in squamous dysplasia associated with carcinoma of the oesophagus: evidence for field carcinogenesis

Squamous epithelial dysplasia is often observed multifocally in the cancerous oesophagus and is presumably considered to be a pre-cancerous lesion. A mutation of the p53 tumour suppressor gene is commonly identified in oesophageal cancer and dysplasia. p53 mutations can be anticipated immunohistochemically. In order to confirm the biological and clinical significance of p53 expressions in oesophageal field carcinogenesis, immunostaining for p53 in cancerous and multifocal precancerous lesions from resected human oesophagus was systematically investigated, while paying special attention to the contiguity of these lesions. Lesions expressing p53 were detected in 46.5% (20 of 43 lesions) of the invasive carcinoma, and in 51.0% (46 of 90 lesions) of the carcinoma in situ, and in 51.4% (92 of 179 lesions) of the dysplasia. Next, the p53 expression in dysplasia was compared with that in carcinoma for the same case. 37 of 39 (94.8%) dysplasias contiguous to p53-positive carcinomas also expressed p53 (P < 0.0001). On the other hand, the isolated dysplasias without contiguity to p53-positive carcinomas, only expressed p53 protein in 44.0% (11 of 25 lesions). No significant correlations were found between the p53 staining and either the clinicopathological features or prognosis. Discordant p53 alterations, such as those seen in cancerous and isolated precancerous lesions, may thus demonstrate further evidence for a multicentric or field carcinogenesis of the human oesophagus. © 2000 Cancer Research Campaig

Investigation into the multiple recent sinkholes in Pokhara, Nepal

Since November 2013, numerous sinkholes have been forming in the Armala area of Pokhara Valley, Central Nepal, posing serious threat to local residents. In order to provide countermeasures for reducing sinkhole risk, detailed investigations into the cause and the formation mechanism of the sinkholes are crucial. Preliminary surveys were conducted in June 2014 and November 2014. Comparison of photos, taken in the two surveys, clearly indicates not only the formation of new sinkholes, but also the re-activation of filled sinkholes. By means of dynamic cone penetration tests and surface wave investigations, qualitative characterization of the soil profile was attained, and shallow weak soil layers which are believed to be the location for future sinkholes could be identified. On the basis of the preliminary field investigation, possible sinkhole formation mechanisms are considered. A risk of sinkhole does not seem to disappear as white turbid water continuously springs. It indicates that the internal erosion of white clayey silt layer is still in progress. In August 2015, a boring was carried out beside one of the largest sinkholes. The overall structure of ground layers was first revealed and a 2.5m high cavity at 7.5-10m deep from the ground surface was found within a thick white clayey silt layer. Further ground investigations including surface wave exploration were conducted in December 2015 and the results are reported

Successful Late Management of Esophageal Perforation with T-Tube Drainage

The late management of spontaneous esophageal perforation is the most challenging problem for the surgeon. In this paper, we present a case in whom a spontaneous esophageal perforation was successfully treated by T-tube drainage after unsuccessful conservative treatment. The patient, a 68-year-old male, was admitted to the hospital with sudden upper abdominal pain. After 2 days, esophageal perforation was diagnosed, and conservative management was begun. Thereafter, the subcutaneous emphysema disappeared, and the patient's temperature decreased. However, on day 13, the patient's temperature spiked above 38°C, and computed tomography showed a mediastinal abscess. An emergency left thoracotomy with laparotomy was performed. Since a 2-cm longitudinal perforation with severe inflammatory reactions was observed, the T-tube drainage method was performed. The patient was discharged without postoperative complications and has not experienced any gastrointestinal symptoms, such as gastroesophageal reflux or dysphagia. In conclusion, the T-tube drainage method appears to be a simple and effective method for the late management of esophageal perforation with severe inflammatory reaction