Elaboration De La Carte Géotechnique De La Ville De Lubumbashi Guide Technique De Sélection Des Sites D’implantation D’ouvrages Du Génie Civil

Geotechnical data processing that ignores the spatial aspect leads to loss of information, specification errors, non-convergent and ineffective estimation, and prediction errors. These data often present a spatial dependence (problem of spatial autocorrelation) and a heterogeneity in space (clustering problem) and sometimes temporal. The geotechnical mapping of Lubumbashi soils based on 1672 observations according to the AASHTO classification system (designation ASTM D-3282 M145), divided these soils into 11 subgroups: A-1-a (sandy gravels with clays), A-1-b (gravelly sands with clays), A-2-4 (gravelly sands with silts), A-2-5 (sandy gravels plastic silts), A-2-6 (gravelly sands with clays), A-2-7 (gravelly sands with active clays), A-4 (silts with sands), A-5 (plastic silts with sands), A-6 (clays with sand), A-7-5 (active clays), A-7-6 (active clays). Class A-3 has not been identified. Soils with an index 5 contain clays of the illite type whereas the others consist of kaolinites on plasticity Casagrande chart. Class A-1 and A-2 are good for foundation engeneering and form the potential aquifers of the city (groundwater, drainage zone, groundwater recharge zone). They also constitute favorable sites for the implantation of the cimeteries (aerated soils) because the time necessary for the destruction of bodies is brief. In this case the rotation of 5 years can be used without problem for a city with dense population like the city of Lubumbashi. Soils A-4 and A-5 are also good for subgrade-foundations, but are highly vulnerable to erosion and liquefaction. Soils A-6 and A-7 form impervious bedrock substrates. These sites can be used as the landfill site. They are also considered clay deposits in the manufacture of ceramics and refractory products. Taking into account the nature of the source rocks, the same lithology can give several types of soils depending on the parameters influencing weathering: climate (Lubumbashi's tropical climate), pH, Eh, topography, anthropization, etc. One type of soil may also come from several rock formations. The geotechnical map developed compared to the geological map of Lubumbashi, shows that soils A-1 and A2 come from conglomerates, sandstones and the lateritization process of rock formations very rich in iron such as dolomitic shale and shale. Soils A-4 and A-5 are often alteration products of silty shales and siltstones, while soils A-6 and A-7 are derived from the alteration of clay and dolomitic rocks: shales, dolomitic shales, silty shales, limestones and dolomites. The geological map is fondamental but not sufficient document for geotechnical studies. A detailed study of the soils and the state of weathering of the different parts of a rock mass is inevitable

Stress rotations and the long-term weakness of the Median Tectonic Line and the Rokko-Awaji Segment

International audienceWe used a field analysis of rock deformation microstructures and mesostructures to reconstructthe long-term orientation of stresses around two major active fault systems in Japan, the Median TectonicLine and the Rokko-Awaji Segment. Our study reveals that the dextral slip of the two fault systems, activesince the Plio-Quaternary, was preceded by fault normal extension in the Miocene and sinistral wrenching inthe Paleogene. The two fault systems deviated the regional stress field at the kilometer scale in their vicinityduring each of the three tectonic regimes. The largest deviation, found in the Plio-Quaternary, is a more faultnormal rotation of the maximum horizontal stress to an angle of 79° with the fault strands, suggesting anextremely low shear stress on the Median Tectonic Line and the Rokko-Awaji Segment. Possible causes of thislong-term stress perturbation include a nearly total release of shear stress during earthquakes, a low staticfriction coefficient, or lowelastic properties of the fault zones comparedwith the country rock. Independently ofthe preferred interpretation, the nearly fault normal orientation of the direction of maximum compressionsuggests that the mechanical properties of the fault zones are inadequate for the buildup of a pore fluidpressure sufficiently elevated to activate slip. The long-term weakness of the Median Tectonic Line and theRokko-Awaji Segment may reside in low-friction/low-elasticity materials or dynamic weakening rather than inpreearthquake fluid overpressures

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Brittle tectonics in the Lufilian fold-and-thrust belt and its foreland. An insight into the stress field record in relation to moving plates (Katanga, DRC)

The Lufilian fold-and-thrust belt also known as the Lufilian Arc and the Kundulungu foreland in the Katanga region (Democratic Republic of Congo) have attracted the attention of several generations of geologists thanks to the discovery of world class Cu-Co ore deposits. Its geological context, tectonic evolution and metallogenesis are relatively well known, in particular for the Neoproterozoic to early Paleozoic, Katangan sedimentary sequences that have been folded and faulted during the Lufilian orogeny as a result of the interaction between the Kalahari and the Congo-Tanzania cratons in the context of the Pan-African amalgamation of Gondwana. The Lufilian Arc and its foreland, as the adjacent Mesoproterozoic Kibara belt, also show signs of active tectonics, with incipient rift basins, diffuse seismicity and thermal springs. This region is presently undergoing continental extension in the context of the poorly defined, embryonic south-western branch of the East-African Rift System. But the tectonic evolution of the Lufilian Arc and its foreland between the paroxysmal deformation stages of the Lufilian orogeny at ~ 550 Ma and the late Neogene to Quaternary development of the south-western branch of the East African rift system, remains poorly understood, although it can be related to an important Cu-dominated mineral remobilization leading to world-class ore deposits. This long period is essentially characterized by brittle tectonics.This research focuses on this long period of brittle tectonics. The outer part of the Lufilian Arc is suitable for this study thanks to well exposed fault-rocks in open mines spread over the entire arc and foreland. In the arc, observations of mesoscopic faults lead to the definition of three different domains (south-eastern, central and north-western), all with diversely oriented faults with breccia and megabreccia. Megabreccia are widespread at regional scale and can be interpreted as a tectonic unit formed during the major Lufilian faulting event. In the south-eastern part of the outer Lufilian Arc, breccia are bordered by thrust faults parallel to the Lufilian trend. In the central part, however, megabreccia are delimited by subvertical faults with variable orientations, at high angle to the trend of the belt. They show either an oblique thrust or a dip-slip reactivation of bedding planes. In the north-western domain, thrust sheets are dominant features. Before this work, the curved architecture of the belt, which reflects the lateral zonation from SE to NW, has been interpreted by some as sourced from a crustal indentation at the last stage of the Lufilian orogeny. We sampled and analysed brittle structures in the Lufilian Arc and its foreland. Our work confirmed the unequal distribution of fault characteristics in the entire outer belt. At each site, dissimilar outcrops provided fault-slip data obeying to a consistent cross-cutting relationship that allowed a chronologic separation. This was used as a criterion for manual separation of large data sets into homogeneous subsets. When computed, coeval sets gave comparable stress tensors. In this work, we reinterpreted the dissimilar geometrical characteristics of the diversely oriented mesoscopic faults that were neglected in previous tectonic models (D1-D3). The presence of large tectonic basins in the arc, its foreland and the Kibara basement that can be correlated with seismotectonic features such as earthquake epicentre and thermal springs, is also taken into account. The modern techniques of fault-kinematic analysis and tectonic stress inversion have been used to resolve these questions. We present new fault-kinematic field observations and paleostress results computed from a database of 1889 fault-slip data at 22 sites by interactive stress tensor inversion and data subset separation. They have been assembled and correlated into 8 major brittle events, their relative succession established primarily from field-based criteria and interpreted in function of the regional tectonic context. The first brittle structures observed were formed during the Lufilian compressional climax, after the transition from ductile to brittle deformation (stage 1). They have been re-oriented during the orogenic bending that led to the arcuate shape of the belt (stage 2). Unfolding the stress directions allowed to reconstruct a well-defined N-S to NNE-SSW direction of compression, consistent with the stress directions recorded outside the belt. Constrictional deformation occurred in the central part of the arc, probably during orogenic bending. After the bending, the Lufilian Arc was affected by a NE-SW transpression of regional significance (stage 3), inducing strike-slip reactivation, dominantly sinistral in the Lufilian Arc and dextral in the Kundelungu foreland. The next two stages were recorded only in the Lufilian Arc. Late-orogenic extension was induced by a &#963;1 &#963;3 stress-axis permutation in a more transtensional regime (stage 4). Arc-parallel extension (stage 5) marks the final extensional collapse of the Lufilian orogen. Stages 2 to 5 are accompanied by important Cu-Co deposits due to fluid circulation in the related brittle mesostructures. In early Mesozoic, NW-SE transpressional inversion (stage 6) was induced by far-field stresses generated at the southern active margin of Gondwana. Finally, this region was affected by still active rift-related extension, successively in a NE-SW direction (stage 7, Tanganyika trend) and NW-SE direction (stage 8, Moero-Upemba trend).The variation of tectonic stresses trough time reflects several first-order geodynamic events that affected a much wider region than the one investigated. The brittle data illustrate several stages of a first geodynamic event related to the Lufilian orogeny, since the onset of the brittle realm, at about 550 Ma ago: from the paroxysm of orogenic compression (stage 1), oroclinal bending (stage 2) to orogenic collapse (stage 5). The oroclinal bending, resulting in the Lufilian Arc, is considered to be constrained by the Kibara belt to the northwest and the Bangweulu block to the east. The related constrictional deformation also lead to accentuated salt tectonics and the formation of tectonic megabreccia prior to the Lufilian transpressional inversion (stage 3). A second geodynamic event (stage 6) was recorded as a transpressional inversion, which is interpreted as a far-field effect of the Gondwanide orogeny as recorded in the Cape fold belt (South Africa) during the early Mesozoic. The effects of the widely recognised late Santonian and late Maastrichtian regional inversion events have not been found. After the early Mesozoic inversion, the Lufilian region has been affected by extensional tectonics related to the break-up of Gondwana. It is not clear when the extensional conditions started, but two major directions of extension apparently succeeded in time (stages 7 &amp; 8), with the last (stage 8) one fitting the current extension directions deduced from earthquake focal mechanisms. Fault-kinematic analysis of brittle structures and the reconstruction of related stress states allowed contributing to an overall geodynamic model of the Lufilian Arc and its foreland. The D1-D3 Lufilian phases are redefined. The new model suggests that only two orogenic phases the D1 (Kolwezian) and D2 (Monwezian) phases are part of the Lufilian orogeny. The D3 (Chilatembo) phase, recorded in orogen-orthogonal structures, is interpreted post-orogenic, related to the previously undocumented far-field stress induced by the Gondwanide collisional transpressional inversion (stage 6). D1 occurred under N-S compression (stage 1) between North and South-Gondwana, Congo-Tanzania and Kalahari cratons respectively. D2 occurred under an NE-SW transpressional inversion (stage 3) during the closure of the Mozambique Ocean caused by the collision between East- and West-Gondwana. Finally, by working on sites with several sub-sites where a large data set can be gathered and which are characterised by a polyphase brittle deformation history, we advanced the methodology of fault-kinematic analysis and tectonic stress inversion by adapting the Win-Tensor program to the context of fold-and-thrust belts. With our experience of the Lufilian Arc, some methodological add-ons such as the interactive data sorting have been developed.nrpages: 182status: publishe

Tectonic stress inversion of large multi-phase fracture data sets: application of Win-Tensor to reveal the brittle history of the Lufilian Arc, DRC

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Minéralisation et context structural au Katanga (RDC)

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Evidence for late Lufilian orogenic mineralizing fluids at the Kamalondo Cu-Co deposit (Tenke Fungurume, Democratic Republic of the Congo)

The Democratic Republic of Congo, part of the Central African Copperbelt, contains numerous Neoproterozoic world-class Cu-Co deposits. The Kamalondo Cu-Co deposit, located in the Tenke Fungurume Mining District, is a mega-fragment of the Mines Subgroup. The Cu-Co mineralization is characterized by a multistage origin, from a diagenetic mineralization, to a syn-orogenic phase (carrollite, chalcocite, chalcopyrite, bornite), and a final supergene enrichment (chrysocolla, heterogenite, malachite). The late Lufilian orogenic Cu-Co mineralization shows carbonate veins (brittle stage 5) crosscutting both carbonate and quartz veins related to brittle stages 1 to 4. The petrography of fluid inclusions reveals the presence of two-phase (liquid and vapor), three-phase, and four-phase inclusions (liquid, vapor and solids, such as anhydride, halite and sylvite). The fluid inclusions microthermometry indicate that the Cu-Co mineralization formed from a fluid with a minimum temperature of 60 degrees C and a salinity >= 26.5eq. wt.% NaCl. These temperature and salinity data are lower than the values typically recorded from the late diagenetic and syn-orogenic stages (homogenization temperature >= 270 degrees C; salinity between 35-45.5 eq. wt.% NaCl)