Carlos Foko TambaLucas KengniPaul TematioDonato Ciampa...
1.1-1.14页
查看更多>>摘要：The environmental impact of the exploitation of geomaterials and their relatively high cost, coupled with the increasingly low financial capital in developing countries, are pushing road actors to turn to inexpensive local ecological materials. The present study is conducted on lateritic graveled soils of Bandjoun (LGSB) in the West Cameroon Region. The aim is to determine whether lateritic gravel soils, particularly those in Bandjoun, can be an ecological and economical alternative to rock aggregates in road construction, considering their geotechnical parameters and environmental impact. These soils were described in the field and were also subjected to complete geotechnical identification in the laboratory. The LGSB presents Californian bearing ratio indices ranging from 26% to 83.3%, a plasticity index of 10.11%, a fines content of 12.05%, an average methylene blue value of 4.25, a water content at the Proctor optimum of 27.6% and a dry density of 1.75 g/cm3. They are silty or clayey gravels and sands of subgroup A-2-7 according to the Highway Research Board classification; sandy and gravelly soils with fines of class B according to the classification of the Road Construction Guide; and silty gravels according to the classification of the Central Laboratory of Bridges and Highways. These soils can be used naturally in pavement layers, in particular in subgrade for all traffic classes and in subbase for low traffic. The tonnage of these soils has been estimated at 18,389 t. The global warming index shows that the use of these soils (18,389 t) in road construction can reduce 31,629–62,706 kg of carbon emissions. The use of lateritic soils in road construction is a very interesting alternative to reduce the environmental impacts associated with the manufacture of rock aggregates. So, lateritic soils should be used instead of rock aggregates for cleaner, more environmentally friendly road construction. The present work presented a specific evaluation of the geotechnical properties and ecological impact of lateritic graveled soils for road construction, as well as their potential for ecological and economic utilization.
查看更多>>摘要：In the Three Gorges reservoir area, the overhead upright pier is the primary structural form. For intelligent monitoring of existing terminals, this research chooses Chongqing Xintian Port as the study object and proposes a support vector machine (SVM) damage-inducing factor (DIF) inversion model based on particle swarm optimization (PSO). To apply the finite element method to analyze the stress distribution characteristics of quay pile groups under three main DIFs, including the stacking effect, ship impact load effect, and bank slope effect. After characterizing the stress data, it becomes evident that there exists a correlation between stress and each DIF parameter. Before generating the training sample set, principal component analysis is employed to reduce dimensionality and eliminate a substantial amount of redundant data. The model has an accuracy of 0.999 for the identification of the type of DIF and 0.975 for the identification of the location of the action of the DIF with F1 coefficients of 0.999 and 0.978, respectively. For the strength of DIF predictions, MAE and MSE were 4.871 and 1.202, respectively, R2 was 0.986, NSE was 0.986, WI was 0.996, and PBIAS was 0.095. After extracting every sample, the relative error for the ship impact load effect is 0.05, and the highest relative error for the bank slope effect is 0.02; the error for the stacking effect is limited to 0.08. The results suggest that the damage inducement inversion model of the SVM optimized by the PSO algorithm can effectively identify the DIF of the overhead upright pier.
查看更多>>摘要：Sixteen groups of comprehensive tests were undertaken to examine the modifications in the mechanical characteristics of weak expansive soil resulting from the inclusion of a composite material comprising cement and jute fibers. The aim of the tests was to analyze the unconfined compressive strength and shear strength. The results reveal that (1) as the modified material content increased, the stress–strain curve of the modified soil progressively became steeper, with a more pronounced peak value. Under the same strain condition, the stress variation increased accordingly. After the stress reached its maximum, a sudden phenomenon of brittle axial compression failure occurred. (2) With the increase in cement content, the unconfined compressive strength and shear strength of the modified expansive soil gradually increased, reaching the highest shear strength when the cement content was 8%. With the increase in jute fiber content, the unconfined compressive strength and shear strength of modified expansive soil increased first and then decreased, reaching the highest value when the content was 0.5%. (3) The cohesion of modified expansive soil increased with the increase in cement content. When the cement content was 8%, the cohesion of the soil sample was as high as 298.29 kPa. The cohesion of modified expansive soil increased first and then decreased with the increase in fiber content. When the jute fiber content was 0.5%, the cohesion reached the maximum value. (4) The internal friction angle of the modified expansive soil increased with the increase in cement content. When the cement content was 8%, the internal friction angle of the soil sample increased by 2.64°. The cohesion of modified expansive soil increased first and then decreased with the increase in fiber content. When the jute fiber content was 0.5%, the internal friction angle reached the maximum value.
查看更多>>摘要：This study investigates the seismic behavior of the T-shaped concrete-filled steel tubular (CFST) column to steel beam joints, aimed at expanding their applicability in areas with high-seismic fortification intensity. A construction form of T-shaped CFST column to steel beam joint with side plates is presented. The variables studied in these experiments include the side plate length, the axial compression ratio, the presence of side plates, and the presence of binding bars. The force mechanism, failure modes, load–displacement curves, strength, stiffness, ductility, and energy dissipation capacity of seven specimens were evaluated under low-cycle reciprocating load. The experimental results demonstrate that the joints of side plates show a full hysteresis curve, with the ductility coefficient ranging from 1.67 to 2.49, and the equivalent viscous damping coefficient between 0.147 and 0.234. The joint panel zone displays strong deformation and energy dissipation capacity. The inclusion of side plates and binding bars improves the seismic behavior of the joint. The setting of side plates enables the formation of a plastic hinge on the steel beam, creating a beam hinge failure mechanism and satisfying the seismic design principle of “strong column and weak beam, strong joint and weak member” as required by the building structures.
查看更多>>摘要：The study presents a development of a nonlinear finite element calculation technique for the prediction of the stability of the multistaged deep excavation in submerged multilayered soft soil retained by steel sheet pile walls structures performed from Cast3M FE code. Optimization numerical backcalculation results are given for the design and construction of retaining walls with adjustment parameters, horizontal displacements, and earth and hydraulic pressure measurements. The difficulties of modeling 2D sheet pile walls in 2D with irregular shapes were overcome by transforming the geometry and stiffness of these sheet steel sheet pile walls into retaining walls of equivalent bending stiffness on the one hand and regular geometric shapes on the other hand. The results of this approach are satisfactory in view of the horizontal displacement curves obtained on the steel sheet pile walls compared by the measures.
查看更多>>摘要：Understanding the mechanical properties of rock is of great significance for the development of unconventional reservoirs. However, a large number of bedding makes the mechanical laws of rock unclear. To investigate the effect of bedding properties on the uniaxial mechanical properties of rock, the coal model containing bedding is developed based on the continuous–discontinuous method, and the effect of bedding angle, bedding strength, bedding number, and loading rate on the uniaxial mechanical properties of rock is investigated. The failure morphology, stress–strain evolution, peak stress, and fracture degrees are analyzed and discussed in detail. The reliability of the numerical model in this paper has been verified by comparison with the indoor experiments. The results show that when the bedding angle is 0°, the peak stress of the rock is maximum, 8.16 MPa, and when the bedding angle is 90°, the fracture degree of the rock is maximum, 3.74%. For the different bedding strengths, the peak stress first decreases linearly with the decrease of the bedding strength. The peak stress barely varies when the bedding strength is less than 0.5 MPa. The fracture degree of the rock shows a nonlinear increase with the increase in bedding strength. For different bedding numbers, the activation of the bedding is not related to the bedding number. The loading speed also has a great influence on the mechanical properties of rock. With the increase in loading rate, the difficulty of bedding activation gradually increases, and the complexity of fractures gradually increases. This study aims to further improve the understanding of the effect of bedding properties on the uniaxial mechanical properties of rock.
查看更多>>摘要：With the ever-increasing number of large-span shield tunneling projects and the extended operational time, their distinctive internal component issues are becoming more pronounced and exhibiting unique characteristics. In order to reveal the cracking mechanism of concrete on the top of the middle partition wall, based on a large-span shield tunnel section of Nanjing Metro, the crack mode, distribution characteristics, and cracking process of concrete inside tunnel structure were studied by combined field investigation and extended finite element analysis. The results showed that: (1) there were 96 cracks of concrete on the top of the middle partition wall in the interval. Based on the propagation path, number, and shape of cracks, they could be divided into type I, II, III, Y, and Z, with type-Y and type-Z being subtypes of type-I. (2) The crack started at the opposite side of horizontal differential displacement of the flue plate. The development curves of the length and end width of type-I and type-II cracks showed the significant characteristics of three stages. The relationship between crack end width and length was nonlinear, showing that 250 and 225 mm, respectively, were the critical crack lengths growing with the rapid growth of the end width of type-I and type-II cracks. (3) In type-II cracks, the propagation curves of two cracks under the same working condition were consistent, and the spacing of plate joints greatly influenced the length and slope of each stage of the curve. For type-III cracks, the first crack propagation process was basically consistent with type-I and type-II cracks, and the propagation of the other two cracks had obvious brittle characteristics.
查看更多>>摘要：Because of the existence of clay minerals such as montmorillonite in red clay, the strength of red clay decreases significantly as water content increases. This study aims to improve the strength of red clay by using three different kinds of industrial solid waste powder, i.e., steel slag (SS) powder, fly ash (FA), and ground-granulated blast furnace slag (GGBS). At the same time, the ordinary Portland cement (OPC) was selected as a comparison of the improvement effect on the strength of red clay modified by the aforementioned industrial solid waste powder. The properties of the red clay and the industrial solid waste powder were documented comprehensively. The unconfined compressive strength (UCS) tests were conducted on the specimens of the red clay and the red clay modified by the OPC, SS, FA, and GGBS, which had been cured for 3, 7, and 21 days at a temperature of 25°C, respectively. The results showed that the strength of red clay can be significantly improved by the three kinds of industrial solid waste powder. After a 21-day curing period, the experimental results showed that the UCS of the red clay modified by 7% SS, 5% FA, and 5% GGBS increased by 252%, 131%, and 140% compared to that of the red clay without modification. However, the modification effects of the SS, FA, and GGBS on the red clay were generally inferior to that of the OPC. By observing the microstructures of the modified clay, the mechanism of industrial solid waste powder and cement improving the strength of the red clay was analyzed. The findings in this study can provide a reference for improving subgrade strength by a soil-modification method in road constructions.
查看更多>>摘要：Foundation settlement prediction is significant to the reuse and management of the reclaimed land from the sea by dykes where composite stratum of many strata with different physical and mechanical properties is encountered. Toward the foundation settlement analysis of reclaimed land in the Yellow Sea composite stratum in eastern China, a weighted-combination model is proposed in this paper combining the hyperbolic model, exponential curve model, and Asaoka model. First, the weight coefficient of the weighted-combination model is calculated by the reciprocal square method of average absolute error (MAE). Second, the settlement prediction results of different models are evaluated by the absolute error, MAE, root-mean-square error, and mean absolute percentage error. Finally, the settlement mechanism of reclaimed foundations in a composite stratum is analyzed from the point of view of the multistratum coupling, and the adaptability of different models to the settlement prediction of reclaimed foundations in a composite stratum is discussed. The results show that the predicted settlement duration curves of the weighted-combined model are in good agreement with the measured settlement duration curves, and the prediction performance is better than that of the hyperbolic model, exponential curve model, and Asaoka model. The MAE of the weighted-combination model is 75.7% lower than that of the exponential curve model, 90.2% lower than that of the hyperbolic model, and 70% lower than that of the Asaoka model. This model provides a new way to predict the settlement of reclaimed foundations in a similar composite stratum.
查看更多>>摘要：A finite element (FE) analysis of corroded circular hollow section T-joints repaired using grouted clamps is presented in this study. To ensure an accurate simulation, experiments on a T-joint with uniform corrosion and an intact T-joint with grouted clamp are reproduced separately using an FE model. The experimental and FE modeling results correlate closely, displaying similar failure behaviors and load–displacement responses. Subsequently, a total of 56 FE T-joint models with varying degrees of corrosion on the chord, repaired by grouted clamp, were then analyzed numerically. The corrosion was artificially applied to the chord’s outer surface at depths of 10%, 20%, and 30% of the chord’s thickness. The models also account for variations in joint geometry, dictated by parameters β and γ, which range from 0.565 to 0.678 and from 21 to 28, respectively. Furthermore, grouted clamp’s properties were examined, including sleeve length, thickness, strength, as well as the thickness and strength of the grout, in relation to the complexity of the repair. The grouted clamp demonstrated significant repair capability, increasing the ultimate strength of the corroded joint by up to 2.23 times. Reinforcements that are both thicker and longer substantially enhance the joint’s ultimate strength. However, inappropriate repair construction results in an abrupt termination of the load–displacement curve and a brittle failure phenomenon outside reinforced chord region. Additional weight from the grouted clamp requires reasonable control, and sleeve overlapping ratio should be guaranteed to be greater than 0.7. The joint bearing capacity can be efficiently increased by thicker grouts and sleeves only in ductile failure cases. The confinement effect and mechanism of the grouted clamp in joint deformation were visually analyzed as stress distribution from FE analysis results. Finally, a prediction equation is proposed to estimate the static strength of the repaired joint through regression analysis.
NETL
NSTL
Wiley