Arching Effect Research Articles

Dynamic correlation between Crude Oil Price and Exchange rate: The Case of ASEAN-5

This study examines the relationship between exchange rate and crude oil price of five Southeast Asia countries including Indonesia, Malaysia, Philippines, Thailand and Singapore from January 1979 to January 2022 using monthly data. Augmented Dickey-Fuller test is used to examine the stationarity of the data. DCC-GARCH model is used to investigate the correlation between oil price and exchange rate. The result shows that skewness, kurtosis, autocorrelation and ARCH effects were found in both oil price and exchange rate. Results suggested that both short run persistence (α) and long run persistence(β) are found to be highly significant for oil price and exchange rate of all countries except Indonesia. Furthermore, the correlation coefficients vary over times for all the countries studied. Negative relationship was found between oil price and exchange rate over most of the periods studied in all countries studied.

CALCULATION OF THE NONLIMITING PRESSURE OF THE FINITE SOIL BEHIND A RETAINING WALL BASED ON THE CURVED SLIDING SURFACE

Calculation of earth pressure of the finite soil between the retaining wall and structure surface is difficult for stability calculation of the retaining wall. Thus, a novel method to calculate the nonlimiting pressure of cohesionless soil having finite width behind a retaining wall was developed to investigate the relationship between soil parameters and the earth pressure of the finite soil. The backfill was assumed to have a cycloidal slip surface through the heel of the wall under the translational mode, and the principal stress deflection caused by the arching effect of the soil was considered. Subsequently, the calculation methods for the nonlimited earth pressure distribution, resultant force, and height of its action point were obtained. In addition, the correctness and rationality of the proposed method were verified by comparing the obtained values to those of previously reported experiments. Results show that the active pressure of the finite soil presents a drum distribution along the retaining wall. The critical sliding surface of the finite soil becomes closer to the retaining wall as the internal friction angle of the soil increases and moves further away from the retaining wall as the soil/wall friction angle increases. The obtained conclusions provide a significantly reference for the design of retaining walls adjacent to buildings. Keywords: Retaining wall; Finite soil; Nonlimited earth pressure; Curved sliding surface; Critical sliding surface

Numerical investigation of dry bulk cargo load during ship vertical motion

The accurate estimation of cargo load is important for designing double bottom structures. However, dry bulk cargo load due to ship acceleration has rarely been investigated in detail. In this study, DEM (Discrete Element Method)-FEM (Finite Element Method) coupling analyses with simplified vessel models were used to evaluate the dry bulk cargo load acting on the bottom plate; the dry bulk cargo and deformation of the bottom plate were expressed by discrete and finite elements, respectively. The analyses for the first time showed the occurrence of a large force near the edge of the bottom plate and small force around the center when the bottom plate was elastic. These forces resulted in the reduction of the bending stress on the bottom plate compared to a condition assuming uniform distribution of the dry bulk cargo load. This result firstly explained that the reduction of the bottom plate bending stress in previous measurements of double bottom strain of a bulk carrier during ocean going. Above non-uniformity of the force distribution was not observed when the bottom plate was rigid. This change in the distribution was caused by the arching effect, which occurred due to interlocking between discrete elements. The amplitude of force redistribution depended on the ratio of the width of the vessels to the height of the aggregate of the discrete elements. The DEM-FEM coupling analyses also showed that an appropriate design of the hopper plate can support the inertia of the discrete element aggregate located above the flat bottom plate, and thereby reduce the force acting on the flat bottom plate.

Face stability analysis of cohesion-frictional soils considering the soil arch effect and the instability failure process

Based on the limit equilibrium method, a new three-dimensional progressive failure model, which includes the upper loose zone and the lower slip zone, is proposed to analyze the stability of a tunnel face. In the model, the ellipsoid of the upper loose zone is discretized into a plurality of frustums. Considering the soil arch effect, the theoretical solution of loose earth pressure under an arbitrary slip surface dip angle is calculated iteratively based on the principal stress rotation theory. The limit support pressure of the three-dimensional failure model is obtained. Then, the accuracy and effectiveness of the new model are verified by comparison with existing model tests and theoretical methods. Finally, the effect of the soil parameters on the limit support pressure is discussed. The relation curve between the loose zone height and the support pressure is determined. The instability failure process of the tunnel face is analyzed. The results show that the internal friction angle and cohesion have significant effects on the limit support pressure. The tunnel face instability failure process is defined. As the height of the loose zone increases, the limit support pressure decreases sharply first, then increases slowly, and finally reaches a fixed value.

A Hybrid Space–Time Modelling Approach for Forecasting Monthly Temperature

Spatio-temporal forecasting has various applications in climate, transportation, geo-statistics, sociology, economics and in many other fields of study. The modelling of temperature and its forecasting is a challenging task due to spatial dependency of time series data and nonlinear in nature. To address these challenges, in this study we proposed hybrid Space–Time Autoregressive Moving Average-Generalized Autoregressive Conditional Heteroscedasticity (STARMA-GARCH) model in order to describe and identify the behaviour of monthly maximum temperature and temperature range in Bihar. At the modelling process of STARMA, spatial characteristics are incorporated into the model using a weight matrix based on great circle distance between the regions. The residuals from the fitted STARMA model have been tested for checking the behaviour of nonlinearity. Autoregressive Conditional Heteroscedasticity-Lagrange Multiplier (ARCH-LM) test has been carried out for the ARCH effect. The test results revealed that presence of both nonlinearity and ARCH effect. Hence, GARCH modelling is necessary. Therefore, the hybrid STARMA-GARCH model is used to capture the dynamics of monthly maximum temperature and temperature range. The results of the proposed hybrid $$\mathrm{STARMA} \left({1}_{1}, 0, 0\right)-\mathrm{GARCH} \left(0, 1\right)$$ model have better modelling efficiency and forecasting precision over $$\mathrm{STARMA }\left({1}_{1}, 0, 0\right)$$ model.

Membrane Effect of Geogrid Reinforcement for Low Highway Piled Embankment under Moving Vehicle Loads

In this paper, the membrane effect of geogrid reinforcement was investigated based on numerical simulation to understand the serviceability and deformation of highway piled embankments under moving vehicle loads. The membrane effect of geogrid reinforcement in low embankments (i.e., the ratio of embankment height to pile spacing is less than 1.5) was clearly emphasized. It has been found that the maximum settlement of geogrid occurs in the central area between the piles, and the maximum tension was concentrated at the corner of the pile cap. Due to the attenuation of the soil arching effect under moving dynamic loads and the punching mechanism, the settlement and tension of the geogrid increased considerably by approximately 35% and 23% compared to those under static loads. A parametric study was also achieved, and the results presented that the geogrid reinforcement tension increased by increasing the pile spacing, embankment height and geogrid stiffness, vehicle wheel load and vehicle velocity. It was also found that the reinforcement tension was most sensitive to the pile spacing among all the parameters considered in this paper, whose magnitude increased by approximately 104% as the pile spacing increased from 2.0 m to 2.5 m under dynamic loads.

Stability Analysis of Shield Excavation Surface with Curved Body Model

Currently, the limit equilibrium method of wedge shape is generally adopted for the stability of the excavation surface in shield tunnel construction. In this method, the sliding surface is approximated by a plane, and the lateral friction force of the sliding surface is estimated and assumed to be a known quantity to derive the equilibrium equation and calculate the support force of the excavation surface. However, it is difficult to accurately estimate the lateral friction force of the sliding surface because of many factors that affect such friction, for example, soil arching. In this paper, a sliding block model of curved surface body composed of a semicircular platform and a partial sphere is proposed for the stability of the excavation surface in shield tunnel construction. By using the symmetry of the surface body model, there is no need for estimating the friction force of the sliding surface during the stability analysis of the excavation surface, and the calculation accuracy of the limit support pressure is improved. Furthermore, the force analysis of the semi-circular platform surface model above the tunnel vault is carried out. Considering the variation of the lateral pressure coefficient caused by the deflection of the principal stress under the soil arch effect, the analytical solution of the vertical stress in the soil is derived when the sliding crack surface is curved. Finally, we present a sensitivity analysis of various parameters affecting the support force of the excavation face through the study of examples. The influencing factors and changing rules related to the support force of the excavation face are also discussed.

Effects of soil arching on behavior of composite pile supporting foundation pit

Effects of soil arching on behavior of composite pile supporting foundation pit

Calculation of Nonlimit Active Earth Pressure against Rigid Retaining Wall Rotating about Base

A retaining wall with sandy fill was considered as the research object in order to study the nonlimiting active earth pressure under the rotation about the base (RB mode). Rankine’s and Coulomb’s earth pressure theories are no longer applicable to the above conditions (RB mode and nonlimiting active earth pressure). In order to improve the traditional earth pressure calculation methods (Rankine and Coulomb), a calculation method using curvilinear thin layer elements is presented with overall considerations of wall displacement, soil arching effect, and friction angle exertion coefficient to deduce the nonlimit active earth pressure under RB. Additionally, the calculation results were in good agreement with model test data (from Fang and Smita). Moreover, a parametric analysis was carried out. It was revealed that the developed value of the shear strength decreased with the depth, and the active earth pressure distribution curve was linear and nonlinear in the upper and lower halves, respectively.

Performance analysis of steel frame joints reinforced against progressive collapse by partially-penetrated butt-welded corrugated steel plates

To evaluate the progressive collapse resistance of reinforced steel frame joints for partially-penetrated butt-welded connections between corrugated steel plates and columns, experiments were conducted on two substructures, each comprising joints above the failed column and half-span beams on both sides. The experimental results were used to verify the established finite element models, before evaluating the effect on the collapse resistance of the welding form between the corrugated steel plates and columns. Furthermore, the seismic performance of steel frame joints reinforced with corrugated steel plates was analyzed. The results show that all specimens experienced a flexural phase with compressive arch action, a stretch-flexural phase, and a catenary phase. Corrugated steel plates can significantly improve the collapse resistance of steel frame joints and benefit the exertion of the catenary mechanism. The finite-element results agreed well with the experimental results. Sliding at the support is a predominant reason for the compressive arching effect and asymmetry of the final failure of the specimens. When the connections formed between corrugated steel plates and columns are partially or fully penetrated by butt welding, the progressive collapse resistance of the substructure is almost unchanged. Although there is no safety margin for joints with the former connection form, it far outweighs the latter for construction and can be widely used in practical projects. Corrugated steel plates can slightly improve the seismic performance of steel-frame joints.

Numerical Study of Bearing Capacity of the Pile-Supported Embankments for the Flexible Floating, Rigid Floating and End-Bearing Piles

Floating pile-supported embankment involves more complex load transfer mechanisms, and there are no clear uniform guidelines available for its design. The concepts of flexible floating, rigid floating and end-bearing pile-supported embankments were proposed in this paper. Based on three typical field cases, their pile-soil interactions and soil arching effect were examined using the three-dimensional finite element method. Due to symmetry, only a half-width embankment model was simulated here. It has been found that the flexible floating piles carry the load mainly relying on the skin friction, but end-bearing piles rely on the pile tip resistance. The rigid floating piles were somehow in between. The earth pressure coefficient (K) in the end-bearing pile-supported embankment reached a maximum of 3.28, greater than Rankine passive values of the earth pressure coefficient (KP), in which the soil arching was fully developed. The K in the embankment with rigid floating pile reached 2.21, where soil arching might be partially formed. At the bottom of the flexible floating pile-supported embankment, the K tended to equal the Rankine active values of the earth pressure coefficient (Ka), and thus soil arching was insignificant. It has also been found that using rigid floating piles might significantly improve the bearing capacity of the embankments and was cost-effective for deep soft soil areas.

Simulated Short- and Long-Term Deformation in Coastal Karst Caves

The self-balanced pressure arch theory is an important basis for excavation support in karst caves, but it is difficult to quantify the empirical theory in coastal areas. In addition, the rheological effects of karst strata could pose a hazard to engineering. Therefore, this study investigated the rheological mechanism under the self-balanced pressure arch effect, and we proposed a mesoscopic unit rheological model for clay minerals in a water-rich environment. With the discrete element method (DEM), we realized the numerical modeling of the rheological model. Then, the proposed model is validated by a case study of foundation excavation in the coastal karst area of China. The mesoscopic mechanical characteristics of caves considering the influence of pressure arch are analyzed. The results show that the self-balance of the caverns mainly lies in the mesoscopic mineral strength and local stress. With the rheological controlled model, the final predicted convergent deformation of the foundation has an error of less than 10% compared with the field monitoring data. In this study, we can quantitively describe the self-balance effect of the pressure arch surrounding the caves and reveal the rheological mechanism. The proposed model can be applied to similar engineering with careful calibration and provide safety guidance.

Finite-Element Analysis on the Tensile Membrane Effect in Geogrid Reinforced Piled Embankment under Dynamic Loading

This study presented a numerical investigation of the tensile membrane effect in the geogrid reinforced piled embankment under dynamic loading. It has been found that the maximum sag of the geogrid was attained at the center of two adjacent piles, while localization of tensile force was observed at the corners of the pile caps. Under the dynamic loading, the sag and the strain of the geogrid increased when compared with the static loading, an increase of around 45.9% and 24% was, respectively, yielded for the sag and the strain of the geogrid. This increase of tension in the geogrid may mainly result from the degradation of the soil arching effect under dynamic loading. A parameter study was performed, and it showed that the tensile force in the geogrid increases with the rise of the embankment height, the clear pile spacing, and the tensile stiffness of the geogrid. However, the increase of the friction angle of the embankment fill led to a decrease in the tension in the geogrid, which may benefit from the improvement of the soil arching developed in the embankment fill. It was found that the tensile behavior of the geogrid was the most sensitive to the pile spacing. When pile spacing increased from 2.0 m to 3.0 m, the tensile force in the geogrid increased by about 248%.

Regulating bulkhead pressure of EPB shield machines through DEM modeling and data mining

Proper regulation of the earth pressure on the bulkhead of earth-pressure balanced (EPB) shield tunneling machines is significant to ensure safe construction. This study proposes a procedure for regulating the bulkhead pressure by combining numerical simulations and data mining, and applies the procedure to a metro line constructed in sandy pebble stratum using EPB shield. Firstly, the relationship between the bulkhead pressure and the pressure on the tunnel face is carefully obtained from discrete element modeling, and the required supporting earth pressure is derived by considering the arching effect. Secondly, aided with the machine learning method, a model is constructed for predicting the average bulkhead pressure per ring according to the operational parameters (i.e., the average driving speed and the rotation speed of the screw conveyor). Given the target value of the bulkhead pressure, the optimal values of the operational parameters are obtained from the model. In addition, an autoregressive moving average stochastic process model is developed to monitor the real-time fluctuation of the bulkhead pressure and guide the actions taken in time to avoid dramatic fluctuations. The results indicate that the pressure difference between the tunnel face and the bulkhead is considerable, and the consideration of the arching effect can avoid overestimating the bulkhead pressure. A combination of the machine learning model and the stochastic process model provides a plausible performance in regulating the bulkhead pressure around the target value without dramatic fluctuation.

Model test and numerical analysis for the face failure mechanism of large cross-section tunnels under different ground conditions

Face stability protection is a critical issue during large cross-section tunneling. This study investigates the evolution mechanism of tunnel face instability with different ground conditions based on model tests and numerical simulations. Eight groups of model tests were conducted to study the failure behavior of the tunnel face and to characterize the ground displacement and stress distributions. Three failure modes including front extrusion, forward caving and backward caving were defined based on the model test results. Finite element limit analyses were performed using the strength reduction method to simulate the failure behavior. The simulation results were compared with those of the model tests, validating the effectiveness the numerical techniques used in the study. Parametric studies were conducted to investigate the effects of ground strength and unit weight, and tunnel unsupported length, height and burial depth on the tunnel face stability. The simulation results showed that the effect of the gravity load on face stability weakens with the increase in the burial depth due to the arching effects as observed in model tests. Since the ground strength, unsupported length and tunnel height significantly influenced the face stability, the bench method with different unsupported length was compared with the full-face method. The effects of upper bench length and height on the face stability under different ground conditions were investigated. This study explored the face failure mechanism of large cross-section tunnels excavated under different ground conditions. The results can provide a reliable reference to evaluate face stability and safety control during tunnel excavation.

Computer simulation of circular plastic compression of a lightning protection cable with an optical module

In the work, using computer simulation, the geometric parameters of the elements of a lightning protection cable (strands of the LK-О type) with an optical module at circular plastic compression are determined. A delay in the formation of side contacts (arch effect) between the wires of the outer layer of the strand of 1 + 9 + 9 structure with a dense lay of elements is established, which creates conditions for transferring pressure to the inner layers and causes a significant (up to 20 %) deformation of the optical module surface at a degree of compression of ql = 5.5 %. In this case, the filling level of inner layer gaps reaches a critical one, which contributes to the transition to the elongation deformation (drawing) of the wires and to a decrease in the longitudinal stiffness of the strand. Violation of the condition of tight laying of the strand elements by choosing the geometric dimensions of the wires during modeling, which ensure the presence of initial gaps between the layers, reduces the deformation on the surface of the optical module to ql = 7–8 % at a degree of compression ql = 6 %, which is explained by more intensive formation of lateral contacts between wires of the outer layer, reducing the radial component of the pressure transmitted inside the strand. It is shown that its reduction can also be achieved by increasing the number of wires in the layers. For a strand of 1 + 10 + 10 construction, in the presence of a gap between the inner layer and optical module, the deformation on the core surface is 3–4 % at a compression ratio of ql = 6.3 %, which ensures the operability of the optical module (core) after circular plastic compression and integrity of optical fibers.

Effect of full arch two scanning techniques on the accuracy of overdenture conventional and CAD/CAM Co-Cr bars

PurposeThis work evaluates the internal and marginal adaptation of implant-assisted overdenture cobalt–chromium (Co–Cr) bars manufactured using conventional as well as CAD/CAM subtractive and selective laser melting (SLM) utilizing two scanning techniques. Methods: An edentulous study model containing four dental implants placed at teeth sites 36, 33, 43, and 46 was used. The study cast was scanned and compared to the virtual casts developed from two scanning techniques, straight and zigzag motion, using the in silico superimposition process. Then, conventional techniques were used to produce full-arch bars that were compared to the bars fabricated using the two scanning techniques and CAD/CAM subtractive and additive techniques. Results: The conventional impression and casting techniques had the smallest marginal gap among the groups (P-value < 0.05). The CAD/CAM subtractive milling techniques in groups II and III had significantly smaller marginal gaps than SLM technique used in groups IV and V (P-value < 0.05). The analysis of the internal gap within each group showed statistically significant differences between different implant sites in all groups (P-value < 0.001), except when using the conventional impression and casting techniques in group I (P-value = 0.20). Conclusion: The conventional impression and fabrication techniques were better than the digital impression and CAD/CAM subtractive and additive techniques for the fabrication of full-arch bars. However, both straight and zigzag scanning techniques and the CAD/CAM subtractive technique had marginal and internal gaps that were within clinically accepted ranges, and the SLM was found to be unsuitable for long-span framework fabrication with either scanning technique used.

Optimized Design of Piled Embankment Using a Multi-Effect Coupling Model on a Coastal Highway

This study presents a multi-effect coupling model to optimize the design of a geosynthetic-reinforced pile-supported embankment (GRPSE) considering the coupling effects of soil arching, membranes, and pile–soil interaction on a coastal highway. The developed model could optimize the design of the GRPSE to fulfill the design and construction requirements at a relatively low project cost. This was achieved by adjusting the critical factors that govern the settlement of GRPSEs, such as pile spacing, tensile stiffness of geosynthetic reinforcement (GR), arrangement of piles, pile cap size, and cushion thickness. The model predictions were validated by a series of field tests using a range of geotechnical sensors. The results show that model predictions agreed with experimental measurements reasonably well. In addition, the results indicate that in comparison to a square arrangement of piles, a triangle net arrangement can decrease the differential settlement of pile soil. Furthermore, this study demonstrates that a change in the GR’s tensile stiffness has little impact on the settlement of GRPSEs. This study can help to improve the stability of roadbeds of coastal highways.

Soil arching effect in reinforced piled embankment for motor-racing circuit: Field tests and numerical analysis

When constructing superstructures on soft soils, severe issues including excessive settlements, bearing failures, and large lateral displacements arise and cause challenges for geotechnical engineers. Reinforced piled embankments are being used increasingly for various types of engineering construction such as highway widening and roadway construction, thereby making it crucial to comprehend and evaluate systematically the effect of soil arching, which has a significant influence on the performance of such embankments. This study focuses on two large-scale field tests of the piled embankments for an international motor-racing circuit in China, and the effect of the load transfer platform formed by geosynthetic reinforcement and gravel layer is investigated. Field monitoring data of soil pressures and settlements of pile caps and soils are reported and analyzed, and the test results show that soil arching acts significantly to transfer the load to the pile caps with an increase in loading from the embankment. Geogrids within the gravel layer can not only improve soil arching (reflected by higher stress concentration ratio) but also diminish differential settlements between pile caps and the ground surface. A numerical test considering different influencing factors is also conducted, thereby enabling both studying the effects of varying the field parameters and comparing with the insitu measurements. A proposed numerical model of the reinforced piled embankment is also shown to work well when compared with the results of the field tests. This study enhances the comprehension of soil–pile–geogrid interactions and guides similar projects in the future.

Impact of currency futures on spot rate volatility in Indian foreign exchange market

The work aimed going to ascertain the efficacy of the currency futures on cash-market or Spot exchange rates volatility with respect of USD/INR, EURO/INR, GBP/INR &amp; JPY/INR. The daily closing of have been taken from RBI website. Also, the time series data is checked for stationarity using ADF test. Existence of ARCH effect examined in spot rate residual of the return series data and checked with Autoregressive conditional heteroskedasticity L.M. test by using GARCH (1,1) model. Findings of GARCH model shows that large volatility is persistent pre-introduction of currency futures and finding shows presence of time-varying conditional volatility of returns of currencies spot prices at pre-post and total period of currency futures introduction in currency exchange market. The variances in volatility of the exchange rate returns of pre and post introduction of currency futures time periods being analyzed by using statistical tools. Findings shows to be importantly varied and volatility has been came down in the post futures era also series were found more stable in terms of volatility.