Time-dependent displacement behaviour of model adfreeze and grouted piles in saline frozen soils

1994 ◽  
Vol 31 (3) ◽  
pp. 395-406 ◽  
Author(s):  
K.W. Biggar ◽  
D.C. Sego
Keyword(s):  
Field Studies ◽  
Frozen Soil ◽  
Silty Sand ◽  
Time Dependent ◽  
Test Results ◽  
Model Pile ◽  
Laboratory Test Results ◽  
Load Carrying ◽  
Pile Deformation

The findings of a laboratory study on the time-dependent displacement of model piles in saline frozen soil are reported. The short-term time-dependent pile deformation in ice-poor saline silty sand was best described using a simple power law of time, whereas the long-term time-dependent deformations were best described using a flow law formulation similar to that used to describe the long-term time-dependent deformation of ice or ice-rich permafrost. The use of cementitious grout as a backfill resulted in doubling of the pile load carrying capacity for a given displacement rate. The laboratory test results compare well with other laboratory and field studies. Key words : frozen soil, saline, model pile, time-dependent deformation, sand backfill, grout.

ESTIMATING LOAD-DISPLACEMENT BEHAVIOR OF SOFT CLAYS

2016 ◽  
Vol 3 (2) ◽  
Author(s):  
Murat Tonaroglu ◽  
Cem Akguner ◽  
Murat E. Selcuk
Keyword(s):  
Laboratory Test ◽  
Field Measurements ◽  
Soil Parameters ◽  
Model Parameters ◽  
Time Behavior ◽  
Test Results ◽  
Engineering Structures ◽  
Laboratory Test Results ◽  
Study Laboratory

Prediction of long term settlement of soft soils below civil engineering structures is an important issue in geotechnical engineering. The data from laboratory consolidation tests are used to estimate the ultimate settlement and problems arise in predicting settlement-time behavior in the field. In order to overcome this difficulty some empirical models or adjustments have been proposed based on field settlement measurements, even if they are available at least for the early stages of loading. In this study, laboratory test results and field settlement measurements obtained for the long term settlement of clayey layers underlying the Alibey Dam in Istanbul, Turkey are used in conjunction with a model proposed by Edil and Mochtar (1984) for peat-like soils. The soil parameters of the proposed model have independently been obtained using both laboratory test data and field measurements, and model predictions are compared with actual recorded settlements. It is observed that the field measurements could be predicted more closely if the model parameters are obtained from field measurements, but predictions based on laboratory consolidation and creep test results also provide satisfactory results following the initial stages of loading.

scholarly journals A Fractional Creep Constitutive Model for Frozen Soil in Consideration of the Strengthening and Weakening Effects

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Feng Hou ◽  
Quanming Li ◽  
Enlong Liu ◽  
Cheng Zhou ◽  
Mengke Liao ◽  
...  
Keyword(s):  
Shear Stress ◽  
Constitutive Model ◽  
Test Specimen ◽  
Confining Pressure ◽  
Frozen Soil ◽  
Strengthening Effect ◽  
Term Strength ◽  
Test Results ◽  
Creep Constitutive Model

The triaxial creep tests of frozen silty clay mixed with sands were performed under different pressures, and the test results demonstrated that, under the low confining pressure, when the shear stress is lower than the long-term strength, the test specimen exhibits an attenuation creep because the strengthening effect is greater than the weakening effect. When the shear stress is higher than the long-term strength, the test specimen exhibits a nonattenuation creep due to the level of the strengthening and weakening effects change in different stages. As the confining pressure increases, the test specimens only exhibit an attenuation creep because of the enhancing strengthening effect. Both the hardening parameter and the damage variable were introduced to describe the strengthening and weakening effects, respectively, and a new creep constitutive model for frozen soil considering these effects was put forward based on the theory of elastoviscoplastic and the fractional derivative. Finally, the model parameters were analyzed and their determination method was also provided to reveal the trend of parameters according to the triaxial test results. The calculated results of the constitutive model show that the proposed model can describe the whole creep process of frozen soil well.

scholarly journals Diabetes Insipidus and Concomitant Myocarditis: A Late Sequelae of COVID-19 Infection

2021 ◽  
Vol 9 ◽  
pp. 232470962199995
Author(s):  
Abu Baker Sheikh ◽  
Nismat Javed ◽  
Abdul Ahad Ehsan Sheikh ◽  
Shubhra Upadhyay ◽  
Rahul Shekhar
Keyword(s):  
Diabetes Insipidus ◽  
Young Male ◽  
Urine Osmolality ◽  
High Serum ◽  
Test Results ◽  
Global Pandemic ◽  
Laboratory Test Results ◽  
Late Sequela ◽  
Endocrine Complications

Severe acute respiratory syndrome coronavirus 2 causes coronavirus disease 2019 (COVID-19), which has become a global pandemic. Apart from the mild features of the disease, long-term complications involve many systems including both endocrine and cardiovascular systems. Myocarditis, secondary to COVID-19, has become a well-known complication of the disease. However, endocrine complications are generally not common, particularly isolated pituitary abnormalities. There is one other report of diabetes insipidus developing as a late sequela of COVID-19. In this article, we report a case of a young male who presented with features of myocarditis but developed diabetes insipidus on day 7 of admission as a long-term complication after recovery from COVID-19 infection. His laboratory test results at the time of developing the complication revealed a high serum sodium level and low urine osmolality. The patient recovered on administration of desmopressin and was discharged after 16 days of hospitalization.

Mucinous cystadenoma of the appendix – case report

2017 ◽  
Vol 89 (2) ◽  
pp. 65-68 ◽  
Author(s):  
Dariusz Janczak ◽  
Mateusz Szponder ◽  
Dawid Janczak ◽  
Michał Leśniak ◽  
Agnieszka Ziomek ◽  
...  
Keyword(s):  
Differential Diagnosis ◽  
Abdominal Pain ◽  
Benign Tumor ◽  
Mucinous Cystadenoma ◽  
Benign Neoplasm ◽  
Test Results ◽  
Imaging Studies ◽  
Laboratory Test Results ◽  
Long Term Prognosis

Tumors of the appendix are extremely rare and constitute about 0.4% of all tumors of the gastrointestinal tract. The most common benign neoplasm is mucinous cystadenoma, which can be found in 0.6% of all excised appendices and it rarely produces any symptoms. We present the case of a female patient who underwent surgery in the Department of Surgery due to suspicion of an appendicular abscess. On the postoperative pathology study, the diagnosis of a tumor of the appendix (mucinous cystadenoma) was made. Mucinous cystadenoma is rarely included in the differential diagnosis of a non-specific abdominal pain accompanied by non-characteristic laboratory test results and imaging studies. There are no unequivocal guidelines and algorithms of managing this disease. Long-term prognosis is good in the case of a benign tumor.

scholarly journals Polypropylene as a Retrofitting Material for Shear Walls

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2503
Author(s):  
Enea Mustafaraj ◽  
Yavuz Yardim ◽  
Marco Corradi ◽  
Antonio Borri
Keyword(s):  
Load Capacity ◽  
Shear Walls ◽  
Experimental Program ◽  
Test Results ◽  
Short Fibers ◽  
Epoxy Adhesives ◽  
Load Carrying ◽  
Energy Dissipation Capacity ◽  
Long Term Behavior

In recent years, on account of their excellent mechanical properties, composite materials (made of epoxy-bonded carbon, glass, or aramid fibers) have been used to reinforce masonry walls against in-plane actions. These materials have proven to be an effective solution for the strengthening of unreinforced masonry (URM) walls. Lately, research has shifted to the study of different types of fibers to avoid the use of epoxy adhesives, whose long-term behavior and compatibility with masonry are poor. This paper describes an experimental program that investigated the behavior of URM shear walls strengthened with two types of commercially available polypropylene products: short fibers (fiber length = 12 mm) and polypropylene nets. This investigation aimed to evaluate the influence of polypropylene reinforcement, embedded into an inorganic matrix, in terms of the improvement of the lateral load-carrying capacity, failure mechanism, ductility, and energy dissipation capacity of URM wall panels, where nine walls were subjected to in-plane loads using a racking test setup. The study showed that using two layers of polypropylene fibers embedded into a cementitious matrix greatly increased the in-plane load capacity of the brickwork masonry. On the other hand, the test results indicated that polypropylene nets, used as a repair method for cracked shear walls, cannot improve the structural performance of the walls.

scholarly journals Performance Improvement in Pile Anchor System for Deep Foundation Excavation Using Electroosmotic Chemical Treatment

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Lei Zhang ◽  
Bing-Hui Wang ◽  
Li-Yan Wang ◽  
Li-Ping Jing ◽  
Chen Fang ◽  
...  
Keyword(s):  
Laboratory Test ◽  
Performance Improvement ◽  
Chemical Treatment ◽  
Field Studies ◽  
Critical Parameters ◽  
Test Results ◽  
Deep Foundation ◽  
Anchor System ◽  
Laboratory Test Results ◽  
Deep Foundation Excavation

Anchoring force is vital to ensure the acceptable performance of a pile anchor system when supporting deep foundation excavation. The soft soil has several physical properties, such as low shear strength, high water content, large void ratio, and high flowability. Traditional grouting and anchoring techniques have demonstrated technical limits to deal with these soil properties in engineering projects, and accordingly, the anchoring force in the pile anchor system is difficult to meet design requirements. This paper conducted an experimental investigation on the performance improvement in a pile anchor system using the electroosmotic chemical treatment method, with an emphasis on the deep foundation application. Experimental tests and field studies were designed to enhance anchor capacity of a pile anchor system using self-designed devices. The laboratory experiments utilized a simplified anchor system in which anchors were designed as the electrodes to conduct the electroosmotic chemical treatment and consolidate the soft marine soil collected from the project site. In addition, static load tests were conducted on the tested soil to measure the anchoring force. Finally, parametric analyses were performed to investigate effects of several parameters on anchoring force in terms of the ultimate pull-out capacity of the anchor, identifying critical parameters for the field study. Based on laboratory test results, field studies were carried out in the Yingkou city. The results from field studies were compared with laboratory test results to validate feasibility of electroosmotic chemical treatment for a pile anchor system.

scholarly journals A Two-to-Five Year Follow-Up of a Pediatric Acute-Onset Neuropsychiatric Syndrome Cohort

2021 ◽  
Author(s):  
Caroline Gromark ◽  
Eva Hesselmark ◽  
Ida Gebel Djupedal ◽  
Maria Silverberg ◽  
AnnaCarin Horne ◽  
...  
Keyword(s):  
Clinical Course ◽  
Acute Onset ◽  
General Function ◽  
Test Results ◽  
Laboratory Test Results ◽  
Relapsing Remitting ◽  
Long Term Prognosis ◽  
Progressive Course

AbstractLittle is known about the long-term prognosis of children with pediatric acute-onset neuropsychiatric syndrome (PANS). Out of the 46 eligible patients from the Karolinska PANS cohort, 34 consented to participate in a follow-up (median 3.3 years). Participants underwent a thorough clinical evaluation and were classified according to their clinical course. Resulting groups were compared on clinical characteristics and laboratory test results. We observed significant reductions in clinician-rated PANS symptom severity and improved general function. Two patients were classified as remitted, 20 as relapsing–remitting, and 12 as having a chronic-static/progressive course. The latter group had an earlier onset, greater impairment and received more pharmacological and psychological treatments. Although remission was rare, the majority of children with PANS were significantly improved over the follow-up period but a non-negligible minority of patients displayed a chronic-static/progressive course and required additional treatments. The proposed definitions of flare and clinical course may be useful in future clinical trials.

Time-dependent behavior of rock-like specimen containing multiple discontinuous joints under uniaxial step-loading compression

2021 ◽  
pp. 105678952098524
Author(s):  
Wendong Yang ◽  
Chunjie Bo ◽  
Xuguang Chen ◽  
Chenchen Huang ◽  
Guizhi Li
Keyword(s):  
Jointed Rock ◽  
Time Dependent ◽  
Tensile Failure ◽  
Term Strength ◽  
Test Results ◽  
Joint Plane ◽  
Discontinuous Joints ◽  
Joint Length ◽  
Rock Specimens

Rock with multiple discontinuous joints widely exists in rock engineering, and its mechanical properties are complex, which greatly increases the difficulty of engineering design and construction. Time-dependent deformation characteristics and long-term strength evaluation of jointed rock masses remain poorly understood. In this work, the creep experiments of rock-like specimens with multiple discontinuous joints under uniaxial step-loading compression are carried out to explore the influence of joint geometry (rock bridge length, joint length, joint angle, and joint spacing) on creep strain, long-term strength, and failure pattern of specimens with multiple discontinuous joints. The following conclusions are drawn from the test results: 1) The deformation of jointed rock specimens has evident time-dependent effect, and the cumulative creep deformation increases as creep load increases; 2) The strength of jointed rock specimens under loading changes with time, and the ratio of long-term strength and creep peak strength ( σ∞/ σc) of the tested specimens ranges from 41% to 96%; 3) The distribution of initial joints affects the creep fracture modes of rock-like specimens. The rupture of rock-like specimens with different joints distribution is mainly caused by the growth of wing cracks and quasi-coplanar secondary cracks. Three different failure modes are observed from these specimens: i) tensile failure with cracks across the joint plane; ii) shear failure with cracks along the joint plane; and iii) tensile failure with cracks along the joint plane. Based on the principles of damage mechanics and fracture mechanics, a theoretical mechanistic model considering both the closure stage of pre-existing open joints and time-dependent propagation stage of new cracks is established. Considering the influence of joint length, joint angle and joint density, the evolution of creep strain of rock-like specimen with multiple discontinuous joints is analyzed. The theoretical model results agree well with the experimental results, which indicates that the established model can replicate the creep failure process of jointed rock mass. These theoretical and test results help us better understand the effect of multiple joints on the long-term behavior of rock mass.

Time-Dependent Finite Element Analysis of Prestressed Concrete Beams

2015 ◽  
Vol 1096 ◽  
pp. 548-552
Author(s):  
Ting Liu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Prestressed Concrete ◽  
Concrete Beams ◽  
Tensile Force ◽  
Time Dependent ◽  
Test Results ◽  
Element Analysis ◽  
Finite Element Software

Based on ABAQUS general finite element software, UMAT Fortran subroutine is compiled to estimate the long-term deflections of prestressed concrete beams. And the calculated values using the software corresponded well with the laboratory results. By generalizing key parameters impact on long−term deflections of prestressed concrete beams, time-dependent finite element analysis was conducted. Taking type of concrete, concrete grade, age of concrete when the initial stress was applied, effective prestressing tensile force, type of prestressed tendon, reinforcement ratio for nonprestressed compression steel reinforcement and mean relative humidity into account, a simplified formula for long-term deflection of prestressed concrete beam at midspan was suggested. And the calculated values using the suggested formula corresponded well with the laboratory and filed test results. The errors were within 10%. However, the calculated errors using the common codes were larger, which resulted in the unsafe values.

Sign in / Sign up

Export Citation Format

Share Document