Expansion Of Cavity Research Articles

Theoretical solution for drained cylindrical cavity expansion in clays with fabric anisotropy and structure

This paper presents a novel, exact, semi-analytical solution for the quasi-static drained expansion of a cylindrical cavity in soft soils with fabric anisotropy and structure. The assumed constitutive model is the S-CLAY1S model, which is a Cam clay-type model that considers fabric anisotropy that evolves with plastic strains, structure and gradual degradation of bonding (destructuration) due to plastic straining. The solution involves the numerical integration of a system of eight first-order ordinary differential equations, three of them corresponding to the effective stresses in cylindrical coordinates, other three corresponding to the components of the fabric tensor and one corresponding to the amount of bonding and another corresponding to the specific volume. The solution is validated against finite element analyses. When destructuration is considered, the solution provides slightly lower values of the effective radial and mean stresses near the cavity wall. Besides, the specific volume is further reduced due to loss of bonding. Parametric analyses and discussion of the influence of soil overconsolidation, expansion of the cavity and initial amount of bonding are presented.

Fused yolk sacs in a case of forked umbilical cord in monochorionic diamniotic twin pregnancy: sonoembryological implications

Forked cord (FC), which presents as a fused insertion of two umbilical cords into a monochorionic placenta, is a rare entity, especially in monochorionic diamniotic (MCDA) twin pregnancies. Herein, we describe a case of a MCDA pregnancy with FC, which showed characteristic findings on first-trimester ultrasound examination. A healthy 29-year-old nulliparous woman presented at 8 weeks of gestation following a positive result on pregnancy self-testing. Transvaginal ultrasound revealed two fetuses with active heartbeats and both had their own amniotic membrane, suggesting a MCDA pregnancy (Figure 1a). Noteworthy was that the two yolk sacs were completely fused (Figure 1b) and the connecting stalks, which are the site of the future umbilicus, were located in close proximity to one another (Figure 1c). On transabdominal ultrasound screening at 16 weeks of gestation (Figure 2a), FC was diagnosed but no other abnormalities were detected. The pregnancy course was uneventful and healthy female babies, weighing 2285 g and 2345 g, were born vaginally at 36 weeks. The umbilical and placental inspection revealed that each umbilical cord had two arteries and one vein, which fused near the placental surface, where the amniotic membranes divided the amniotic cavities (Figure 2b). Most cases of previously reported FC were observed in monochorionic monoamniotic (MCMA) twin pregnancies, which were frequently accompanied by an acardiac twin1, 2. Thomas et al. was the first to report an antenatally diagnosed case of FC in an otherwise uncomplicated MCDA pregnancy, in which FC was recognized at 30 weeks, and healthy infants (weighing 2460 g and 2490 g) were delivered at 35 weeks3. Frisch et al. reported a case of FC in a MCMA pregnancy diagnosed at 10 weeks, in which the twin pair (weighing 1169 g and 935 g) was delivered at 29 weeks because of abnormal fetal heart rate patterns4. In our case, which is the third report in the literature of liveborn twins with prenatal diagnosis of FC, the unique findings were the fused yolk sacs, with the amniotic membranes dividing the two fetuses as early as 8 weeks of gestation, in addition to the closely located connecting stalks. From an embryological viewpoint, the folding of the embryo and the expansion of the amniotic cavity, which bring the connecting stalk and yolk sac together to form the umbilical cord, occur after 9 weeks of gestation5. We postulate that our findings at 8 weeks of the fused yolk sacs and the closely located connecting stalks might be forecasting subsequent FC, even when the amniotic membranes dividing two embryos are visualized. As for the blood volume balance between the twins, we agree with the speculation of Thomas et al. and Frisch et al. that a fenestration between the two umbilical vein walls may have had a protective effect on the hemodynamic status of the twins3 and that FC itself in MCMA and MCDA pregnancies does not necessarily cause adverse perinatal outcome4. Our first-trimester findings provide new insights into sonoembryology, especially in relation to umbilical cord development from connecting stalks.

Association of ADRB2 gene polymorphism with dilated cardiomyopathy

Aim. To study the association of the rs1042713 polymorphism of the ADRB2 gene with cardiomyopathies of various origins.
 Material and methods. The study included patients with dilated cardiomyopathy (DCMP) and myocardial dilatation of ischemic genesis (DM IG).The total number of people surveyed is 221. The average age of the subjects was 55.309.69 years. Patients were divided into 2 groups: one of them patients with a diagnosis of dilated cardiomyopathy idiopathic (predictors of expansion of the heart cavities are excluded) and the other-patients with dilated myocardium of ischemic origin (a history of IHD). The number of patients in the first group was 111, including 99 (89.2%) men and 12 (10.8%) women. The average age of patients in this group is 51.739.74 years. The second group included patients with myocardial dilatation of ischemic origin. Their number is 110 people, including 100 (91.5%) men and 10 (8.5%) women. The average age of the respondents is 58.688.38 years. The control group consists of individuals who did not have any manifestations of cardiovascular diseases. Their number is 221 people (average age 53.64.8 years). Laboratory and instrumental studies, coronary angiography, and molecular genetic studies of the rs1042713 polymorphism of the ADRB2 gene were performed for all participants in the study. Those patients who were excluded predictors of the occurrence of dilation of the heart cavities were assigned to the first group. The second group included patients with a history of CHD.
 Results. In the group with DCMP, 10.8% of patients were carriers of the common homozygous AA genotype, the heterozygous AG genotype 48.6%, and the rare homozygous GG genotype 40.5%. In the group of patients with DM IG, 16.4% of patients were carriers of the common homozygous AA genotype, the heterozygous AG genotype 51.8%, and the rare homozygous GG genotype 31.8%. In the control group, 11.8% of patients were identified as carriers of the homozygous genotype for the common allele, 47.5% carriers of the heterozygous genotype, and 40.7% carriers of the homozygous genotype for the rare allele. No statistically significant results were obtained in the group of patients with DCMP and DM IG compared to the control group of the rs1042713 polymorphism of the ADRB2 gene.
 Conclusion. No association of ADRB2 gene rs1042713 polymorphism with DCMI and DM IG was revealed.

Avoiding anticoagulation drugs for postoperative atrial fibrillation enabled successful conservative treatment of left atrial dissection: a case report

BackgroundLeft atrial dissection is a rare complication of cardiac surgery, most commonly associated with mitral valve surgery. Herein, we report on the successful conservative treatment of left atrial dissection while avoiding anticoagulation therapy.Case presentationA 64-year-old man developed left atrial dissection during operation for acute type A aortic dissection, most likely due to retrograde cardioplegia cannulation. As there was no connection between the left atrial dissection cavity and the left atrium on enhanced computed tomography, we did not administer anticoagulants to prevent expansion of the left atrial dissection cavity. However, the patient developed atrial fibrillation, which was successfully managed by beta-blocker and amiodarone administration. Follow-up imaging showed gradual left atrial dissection reduction, and the patient was started on anticoagulation therapy.ConclusionWe were able to resolve left atrial dissection by preventing the use of anticoagulation therapy in the acute stage by managing the atrial fibrillation with antiarrhythmic drugs.

Precise Assembly and Supramolecular Catalysis of Tetragonal- and Trigonal-Elongated Octahedral Coordination Containers

The construction of distorted or irregular coordination polyhedrons with specific shapes and functionalities is highly challenging. Here, we demonstrate a viable strategy for attaining a severely d...

Size effects on the plastic shock formation in steady-state cavity expansion in porous ductile materials

In this paper, we have studied the hypervelocity expansion of a spherical cavity in an infinite medium modeled with the extension of the porous plasticity criterion of Gurson (1977) developed by Chen and Yuan (2002) to account for plastic strain gradient induced size effects. Following the self-similar, steady-state solution derived by Cohen and Durban (2013) for size-independent porous materials, we have computed the critical cavity expansion velocity which leads to the emergence of plastic shock waves for a wide range of initial void volume fractions and different values of the length scale parameter that controls the effect of size. We have shown that size effects hinder the emergence of plastic shock waves, so that as the length scale parameter increases, the expansion velocity required for the plastic shock to be formed increases. In addition, while porosity favors the formation of plastic shocks, as shown by Cohen and Durban (2013), our results indicate that the effect of initial void volume fraction on plastic shock wave formation decreases for size-dependent materials.

Sequential conformational changes in transmembrane domains of presenilin 1 in Aβ42 downregulation.

Alzheimer disease (AD) is the most common neurodegenerative disease worldwide. AD is pathologically characterized by the deposition of senile plaques in the brain, which are composed of an amyloid-β peptide (Aβ) that is produced through the multistep cleavage of amyloid precursor protein (APP) by γ-secretase. γ-Secretase is a membrane protein complex, which includes its catalytic subunit presenilin 1 (PS1). However, much about the structural dynamics of this enzyme remain unclear. We have previously demonstrated that movements of the transmembrane domain (TMD) 1 and TMD3 of PS1 are strongly associated with decreased production of the Aβ peptide ending at the 42nd residue (i.e. Aβ42), which is the aggregation-prone, toxic species. However, the association between these movements as well as the sequence of these TMDs remains unclear. In this study, we raised the possibility that the vertical movement of TMD1 is a prerequisite for expansion of the catalytic cavity around TMD3 of PS1, resulting in reduced Aβ42 production. Our results shed light on the association between the conformational changes of TMDs and the regulation of γ-secretase activity.

Controllable combustion behaviors of the laser-controlled solid propellant

Microsatellites have been widely applied in the fields of communication, remote sensing, navigation and science exploration due to its characteristics of low cost, flexible launch mode and short development period. However, conventional solid-propellant have difficulties in starting and interrupting combustion because combustion is autonomously sustained after ignition. Herein, we proposed a new type of solid-propellant named laser-controlled solid propellant, which is sensitive to laser irradiation and can be started or interrupted by switching on/off the continuous wave laser. To demonstrate the feasibility and investigate the controllable combustion behaviors under different laser on/off conditions, the combustion parameters including burning rate, ignition delay time and platform pressure were tested using pressure sensor, high-speed camera and thermographic camera. The results showed that the increase of laser-on or laser-off duration both will lead to the decrease of propellant combustion performance during re-ignition and re-combustion process. This is mainly attributed to the laser attenuation caused by the accumulation of combustion residue and the change of chamber ambient temperature. Simultaneously, the multiple ignition tests revealed that the increased chamber ambient temperature after combustion can make up for the energy loss of laser attenuation and expansion of chamber cavity. However, the laser-controlled combustion performance of solid propellant displayed a decrease trend with the addition of ignition times. Nevertheless, the results still exhibited good laser-controlled agility of laser-controlled solid propellant and manifested its inspiring potential in many aspects of space missions.

Elastoplastic solution of drained expansion of a cylindrical cavity in structured soils considering structure degradation

An elastoplastic solution of drained cylindrical cavity expansion is presented based on a well-known critical state model for soils exhibiting a natural structure. The model referred to as the structured Cam-clay (SCC) model is capable of describing the properties of the soil structure and its subsequent stress-induced degradation. The asymmetric stiffness matrix of the elastoplastic constitutive equation for structured soils is derived due to the assumption of the non-associated plastic flow rule. The solution procedure is formulated by transforming the boundary value problem of cylindrical cavity expansion into the problem of solving four ordinary differential equations with three stress components and the specific volume as the basic unknown variables. The theoretical solution is numerically calculated and validated against the existing solution and finite element simulation results. Furthermore, the significance of the soil structure and its stress-induced degradation in the expansion response, and the interaction between the soil structure and overconsolidation are emphasized by extensive parametric analyses. The results demonstrate that the soil structure has a substantial influence on the cavity expansion response, and its degradation is closely related to overconsolidation. Particularly, among the solutions considered, the solution considering the soil structure provides higher effective stress values near the cavity surface due to the additional strength conveyed by the natural structure.

Adiabatic heating effect in elastic-plastic contraction / expansion of spherical cavity in isotropic incompressible material

The paper presents an analytical solution to the coupled problem of spherically symmetric elastic-plastic deformation accompanied by heating of the material due to the plastic dissipation, which in turn changes the mechanical properties of the material. The dependence of both elastic and plastic mechanical properties of the material on temperature can be arbitrary. Both elastic and plastic deformations are assumed to be finite. The thermal expansion of material is neglected. Heating is assumed to be adiabatic. Instead of a spatial coordinate, temperature is considered as an independent monotonic variable. This made it possible to reduce the problem to solving the first order ODE. The obtained solution is valid for any incompressible hyperelastic solid with arbitrary pressure-independent non-singular yield condition, perfectly-plastic or isotropic strain-hardening/softening. Example of solution for the linear thermal-softening and strain hardening material with tension-compression asymmetry in yielding is given.

An elastoplastic solution to undrained expansion of a cylindrical cavity in SANICLAY under plane stress condition

Although cylindrical cavity expansion under plane stress condition is commonly encountered in geotechnical problems, most currently available solutions have been developed for cavity expansion under plane strain condition. This paper develops a novel elastoplastic solution for undrained expansion of a cylindrical cavity in SANICLAY under plane stress condition. The SANICLAY model, which could well represent the mechanical behaviour of the anisotropic soil and overconsolidated soil, is employed in the present solution to model the responses of the soil around the expanded cavity. The problem is formulated as a system of first-order differential equations with the unknown variables as the functions of an auxiliary coordinate, which are solved as an initial value problem. The expansion responses under plane stress condition are comprehensively compared with those under plane stress condition to highlight the unique expansion responses under plane stress condition. The results show that the present solution could well reflect the unique expansion responses under plane stress condition, which are totally different from those under plane strain condition. It is expected the proposed solution could provide a reasonable approach to interpret the pressuremeter test and model pile installation effects near the surface of the natural anisotropic clays.

A Dynamic expansion of a cylindrical cavity in a compressible elastic-plastic medium. The Analysis of medium resistance to dynamic penetration of a sharp-nosed impactor

This paper presents the solution of the problem related to the dynamic cylindrical cavity expansion in a compressible elastic-plastic medium. Finite strains, nonlinear compressibility and dependence of the yield stress versus pressure are taken into account in the problem formulation. The study targets at developing a new engineering model on the penetration of a sharp-nosed impactor in the range of middle impact velocities based on the problem analysis results of the cylindrical cavity expansion in a half-space (cylindrical cavity expansion approximation). Based on the analytical approach a model is obtained that determines the resistance of the medium to dynamic cavity expansion. The main parameters of the model depend on the mechanical properties of the medium. For these dependences we proposed approximating relations based on manipulation of the mechanical properties of a number of materials (some alloys and soils). To derive the dynamic penetration model the A.Ya. Sagomonyan assumption of the radial expansion of the hole is used. It is assumed that particles of the medium material move in a radial direction from the surface of the impactor penetrating into the shield. Such assumption can be applied for the class of impactors in the form of slender sharp-nosed bodies of revolution. Based on the assumptions we obtained a model of the medium resistance to the dynamic penetration of a slender sharp-nosed body of revolution. The new model, in addition to the "standard" strength and inertial components, contains the "attached mass", which changes during the penetration process. The experimental validation of the new penetration model using a series of experimental studies on the penetration of various forms of impactors into aluminum alloys is considered. The influence of the “attached mass” and inertial forces of the medium resistance to the penetration is estimated. The conditions of applicability of the new model are obtained: the penetration model is applicable for estimation of the resistance of a compressible medium to penetration of a thin sharp-nosed body of revolution at impact velocities of 200-800 m/s.

Long bone histomorphogenesis of the naked mole-rat: Histodiversity and intraspecific variation.

Lacking fur, living in eusocial colonies and having the longest lifespan of any rodent, makes naked mole-rats (NMRs) rather peculiar mammals. Although they exhibit a high degree of polymorphism, skeletal plasticity and are considered a novel model to assess the effects of delayed puberty on the skeletal system, scarce information on their morphogenesis exists. Here, we examined a large ontogenetic sample (n=76) of subordinate individuals to assess the pattern of bone growth and bone microstructure of fore- and hindlimb bones by using histomorphological techniques. Over 290 undecalcified thin cross-sections from the midshaft of the humerus, ulna, femur, and tibia from pups, juveniles and adults were analyzed with polarized light microscopy. Similar to other fossorial mammals, NMRs exhibited a systematic cortical thickening of their long bones, which clearly indicates a conserved functional adaptation to withstand the mechanical strains imposed during digging, regardless of their chisel-tooth predominance. We describe a high histodiversity of bone matrices and the formation of secondary osteons in NMRs. The bones of pups are extremely thin-walled and grow by periosteal bone formation coupled with considerable expansion of the medullary cavity, a process probably tightly regulated and adapted to optimize the amount of minerals destined for skeletal development, to thus allow the female breeder to produce a higher number of pups, as well as several litters. Subsequent cortical thickening in juveniles involves high amounts of endosteal bone apposition, which contrasts with the bone modeling of other mammals where a periosteal predominance exists. Adults have bone matrices predominantly consisting of parallel-fibered bone and lamellar bone, which indicate intermediate to slow rates of osteogenesis, as well as the development of poorly vascularized lamellar-zonal tissues separated by lines of arrested growth (LAGs) and annuli. These features reflect the low metabolism, low body temperature and slow growth rates reported for this species, as well as indicate a cyclical pattern of osteogenesis. The presence of LAGs in captive individuals was striking and indicates that postnatal osteogenesis and its consequent cortical stratification most likely represents a plesiomorphic thermometabolic strategy among endotherms which has been suggested to be regulated by endogenous rhythms. However, the generalized presence of LAGs in this and other subterranean taxa in the wild, as well as recent investigations on variability of environmental conditions in burrow systems, supports the hypothesis that underground environments experience seasonal fluctuations that may influence the postnatal osteogenesis of animals by limiting the extension of burrow systems during the unfavorable dry seasons and therefore the finding of food resources. Additionally, the intraspecific variation found in the formation of bone tissue matrices and vascularization suggested a high degree of developmental plasticity in NMRs, which may help explaining the polymorphism reported for this species. The results obtained here represent a valuable contribution to understanding the relationship of several aspects involved in the morphogenesis of the skeletal system of a mammal with extraordinary adaptations.

Effects of Obesity and Spirometric Ventilatory Status in Male Medical Students of Amritsar

ABSTRACT Aim and objective To study the effects of obesity on the pulmonary functions in male medical students of Amritsar. Materials and methods Pulmonary function tests (PFTs) of normal, healthy, male medical students of Amritsar were determined and were compared and correlated with other studies. Criteria for obesity in our study taken were according to WHO criteria of BMI. The PFTs were carried out with a computerized spirometer “Med-Spiror”. The data were collected; compiled, statistically analyzed, and valid conclusions were drawn. Higher lung volumes and flow rates were achieved. Results There was a statistically highly significant decline in forced vital capacity (FVC) in obese when compared with nonobese groups. The values of forced expiratory volume in first second (FEV1) in both groups when were compared showed significant changes. The ratio of FEV1/FVC, the values of peak expiratory flow rate (PEFR), and forced mid-expiratory flow (FEF25–75%) showed insignificant changes but maximum voluntary ventilation (MVV) when were compared showed highly significant changes. Conclusion There is a decline of various respiratory functions in obesity. The cause of the decline of various respiratory functions in obesity may be due to a decrease in distensibility of the chest wall or limited expansion of the thoracic cavity and is the cause for reduced ventilatory volumes and total lung capacity. How to cite this article Mahajan S, Hundal GS, Arora AK, et al. Effects of Obesity and Spirometric Ventilatory Status in Male Medical Students of Amritsar. AMEI's Curr Trends Diagn Treat 2020;4(2):74–77.

Glial Tumors Of The Brain, With Associated Hydrocephalia

Despite significant advances in oncology and neurosurgery, glial brain tumors continue to be an urgent problem of modern healthcare. The proportion of gliomas in the total structure of glial neoplasms is 40-45%, mainly they are detected at the age of 30-60 years, affecting the most able-bodied part of the population. Glial neoplasms, as a rule, develop from cells of the astrocytic or oligodendrocytic population and are characterized by a rapid growth rate of the primary tumor node, invasiveness, a tendency to early metastasis, a high recurrence rate, and a poor prognosis. The primary importance of tumor removal in the treatment of the disease is also generally recognized in cases where the pathological process is complicated by persistent disorders of the cerebrospinal fluid, deformation and expansion of the cerebrospinal fluid cavities. Naturally, the development of hydrocephalus, especially hydrocephalic-hypertensive syndrome, changes the course and prognosis of the disease and requires significant correction of the diagnostic and therapeutic process. As with most malignant tumors, anaplastic types of gliomas are characterized by the intensive development of the pathological vasculature, which accelerates the growth rate of the neoplasm, the rate of invasion and metastasis, and also increases the risk for patients due to the possibility of hemorrhage into the tumor. The nodular type of growth with a clearly defined border and insignificant infiltration is less common in conditionally benign gliomas, which have a more favorable prognosis of treatment. In the end, it is concluded that the described methods do not exhaust all proposals for increasing the effectiveness of the treatment of glial tumors and the development of new methods will bring neurooncologists closer to solving this urgent problem.

Idiopathic normal pressure hydrocephalus and Alzheimer's disease in clinical practice: comorbidity and differentiation

The idiopathic normal pressure hydrocephalus (Hakim – Adams syndrome) is characterized by the expansion of cerebrospinal cavities, which is clinically manifested by triad symptoms: cognitive impairment, impaired gait and urination. In this research the severity and modality of cognitive impairment, the pattern of gait changes and the levels of protein biomarkers of amyloidosis and neurodegeneration and neuroimaging changes was evaluated for idiopathic normal pressure hydrocephalus, Alzheimer's disease and their combination. It has been established that for patients with idiopathic normal pressure hydrocephalus the most characteristic is the dysregulatory type of disorders of higher brain functions, while for patients with a combination of Alzheimer's disease and idiopathic normal pressure hydrocephalus, mnemonic disorders are also detected. The specific changes of cerebrospinal fluid in patients with idiopathic normal pressure hydrocephalus are higher levels of amyloid beta, a decrease concentration of tau and phosphorylated tau-protein compared to patients with Alzheimer's disease. In the case of a combination of diseases (comorbidity), it was characterized by intermediate results by cerebrospinal fluid biomarkers. We also revealed patterns of transformation of moderate cognitive impairment into dementia (according to the ratio of tau/Aβ‑42 and ftau /Aβ‑42). The value of evaluating the results of magnetic resonance imaging using special techniques that evaluate both the expansion of the ventricular system and atrophy of the brain parenchyma. Comorbid patients are characterized by a combination of these processes based on the results of neuroimaging. That is why it is necessary to use complex visually analog neuroimaging scales for differential diagnosis and establishing diagnosis. Also, in the course of this work, an algorithm is proposed for mandatory clinical-neuropsychological and laboratory-instrumental examination of patients with cognitive impairment in idiopathic normal pressure hydrocephalus, Alzheimer's disease and their combination.

Effect of primary creep on the relationship between indentation and uniaxial creep: A theoretical model

In this work, a theoretical model is developed to address the effect of primary creep on the relationship between indentation and uniaxial creep tests. By considering the expansion of a spherical cavity in the materials following the primary creeping law, a general expression of the conversion factor is deduced during the primary creep stage. For creep tests with spherical and flat punch indenters, a closed-form formula is specified for the conversion factor that is determined by the stress exponent and hardening exponent. By further considering the difference of the critical time at the onset of steady-state creep deformation between uniaxial and indentation creep tests, it becomes available to convert the indentation creep data into uniaxial creep results during the steady-state creep stage. The rationality and accuracy of the proposed model are verified by comparing with the experimental data of Sn37Pb solder, AZ31 Mg alloy and Succinonitrile. Furthermore, the comparison with previous theoretical models indicates that the ignoring of primary creep effect could lead to the deviation of converted indentation creep data from uniaxial creep results.

104 H. Bruchon. Dilatation uterine avec des laminaires. Perforation incomplete de la levre posterieure du col. (Nouv. Arch. D Obstetr. Et de Gynec. No. 5, 1892). Dilation of the uterus with kelp. Incomplete perforation of the posterior lip of the cervix.

The author, reporting the medical history of one patient, whom he, about the endometritis of the cervix and the body of the uterus and left-sided catarrhal salpingitis, made the expansion of the uterine cavity with kelp for curettage.

Gas injection test of remolded saturated soil with consolidation

Investigation of gas migration in saturated soil is of great theoretical and practical significance in marine science and engineering. The transport of gas bubbles in soil and its effects on soil physical and mechanical properties can be further studied. Gas injection and permeability tests were conducted using a self-developed oedometer with gas injection and water infiltration. Before the gas injection test, the remolded saturated soil was consolidated in an oedometer device to an effective vertical stress of 100 kPa. Gas injection tests were then performed to investigate the transport mechanism of bubbles in saturated soil and the changes in water permeability after gas injection. The results show that it is difficult for gas to migrate through capillary invasion and fracturing from the pore scale owing to the high gas entry pressure in fine-grained sediments. Hence, initial gas migration mechanism in pore scale is elastic-plastic expansion. The scale of cavities expands from micron to millimeter during gas injection, and gas pressure for fracturing reduces with the expansion of cavities. The fracturing initiated in millimeter scale and gas invades further into the soil. Interconnections of cavities and cracks resulting in an increasing of drainage rate and coefficient of permeability.

Centrifuge Modeling of Embankment Failure due to Underground Cavity and Its Electrical Resistivity Monitoring

In this paper, embankment or levee failure due to the interaction between a cavity within an embankment body and high water level was simulated in a centrifuge test and monitored by electrical resistivity tomography (ERT) survey technique. As the centrifuge modeling is an effective research tool for levee stability analysis and the ERT survey is generally adopted in field for health monitoring of levee, physical modeling of levee stability problem and its monitoring by the ERT survey in the centrifuge provides a great opportunity for researchers. Initially, 1 g preliminary test was performed for simulating the underground cavity using a buried ice block to ensure the simulation of such cavity in the centrifuge model. Subsequently, 20 g centrifuge test was performed. At the 20 g-level, over the three stages' water level in river side was maintained to simulate expansion of the underground cavity with increase in groundwater level. Continuous ERT survey was simultaneously conducted to monitor the variation of internal state of the embankment body. During the final high water level, subsidence of levee surface occurred at the vertical location on top of the cavity which can lead to embankment failure. The ERT results (two dimensional contour plots) from the centrifuge test correspond well to the expected process of levee subsidence caused by upward development of inner cavity by showing definite resistivity difference between the cavity and adjacent soil. From the centrifuge test, it is concluded that the cavity within the embankment body could induce failure upon interacting with the high water level, and the ERT monitoring could effectively capture the geotechnical process which shows the upward development of underground cavity.