Xuan-chen Ding, Dingxin Zhang, Chenglong Wang, Gangqiang Kon, Haojie Lu
In recent years, energy piles have been widely used in the collection of shallow geothermal energy. However, the engineering characteristics of the soil and the mechanical behavior of the pile are affected by temperature, especially in clay. To explore the influence of heating-cooling cycles on the thermo-mechanical response of an energy pile in saturated clay, a laboratory model test was designed. The energy pile in saturated clay was subjected to ten heating-cooling cycles. A fiber Bragg grating (FBG) system was adopted to monitor the pile strain. Meanwhile, pile and soil temperature, pore water pressure, and pile top displacement data were collected by a dynamic acquisition instrument. The results show that FBG sensors can achieve good results in measuring the axial strain of the pile. The distribution and transmission of thermally induced axial force and stress are affected by soil properties and pile constraints. Temperature cycling will lead to the thermal consolidation of saturated clay, improving the bearing performance of energy piles, and to an irreversible settlement of the energy pile.
{"title":"Investigation on thermo-mechanical response of energy piles in saturated clay based on an FBG system","authors":"Xuan-chen Ding, Dingxin Zhang, Chenglong Wang, Gangqiang Kon, Haojie Lu","doi":"10.1680/jenge.22.00120","DOIUrl":"https://doi.org/10.1680/jenge.22.00120","url":null,"abstract":"In recent years, energy piles have been widely used in the collection of shallow geothermal energy. However, the engineering characteristics of the soil and the mechanical behavior of the pile are affected by temperature, especially in clay. To explore the influence of heating-cooling cycles on the thermo-mechanical response of an energy pile in saturated clay, a laboratory model test was designed. The energy pile in saturated clay was subjected to ten heating-cooling cycles. A fiber Bragg grating (FBG) system was adopted to monitor the pile strain. Meanwhile, pile and soil temperature, pore water pressure, and pile top displacement data were collected by a dynamic acquisition instrument. The results show that FBG sensors can achieve good results in measuring the axial strain of the pile. The distribution and transmission of thermally induced axial force and stress are affected by soil properties and pile constraints. Temperature cycling will lead to the thermal consolidation of saturated clay, improving the bearing performance of energy piles, and to an irreversible settlement of the energy pile.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42117528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-17DOI: 10.3390/geotechnics3020021
Kazi Moinul Islam, S. Gassman
The new Mechanistic-Empirical Pavement Design Guide (MEPDG) uses the subgrade resilient modulus (MR) as the key input parameter to represent the subgrade soil behavior for pavement design. The resilient modulus increases with an increase in confining pressure, whereas, for an increase in deviatoric stress, it increases for granular soils and decreases for fine-grained soils. The value of MR is highly stress dependent, with the stress state (i.e., bulk stress) a function of the position of the materials in the pavement structure and applied traffic loading. Applying excessive vertical stress at the top of the subgrade without knowing the appropriate stress state can result in permanent deformation. In situ stress must be calculated so the correct resilient modulus can be determined. To facilitate the implementation of MEPDG, this study develops a methodology to select the appropriate subgrade resilient modulus for predicting rutting and IRI. A comprehensive research methodology was undertaken to study the effect of in situ or undisturbed subgrade MR on pavement performance using the MEPDG. Results show that MR obtained from in situ stress is approximately 1.4 times higher than the MR estimate from NCHRP-285. Thus, the in situ stress significantly affects the calculation of subgrade MR and, subsequently, the use of MR in the predicted rutting, with IRI using the AASHTOWare pavement mechanistic-empirical design. Results also show that the pavement sections were classified as in “Good” and “Fair” conditions for rutting and IRI, respectively, considering in situ MR.
{"title":"Effect of the Field-Stress State on the Subgrade Resilient Modulus for Pavement Rutting and IRI","authors":"Kazi Moinul Islam, S. Gassman","doi":"10.3390/geotechnics3020021","DOIUrl":"https://doi.org/10.3390/geotechnics3020021","url":null,"abstract":"The new Mechanistic-Empirical Pavement Design Guide (MEPDG) uses the subgrade resilient modulus (MR) as the key input parameter to represent the subgrade soil behavior for pavement design. The resilient modulus increases with an increase in confining pressure, whereas, for an increase in deviatoric stress, it increases for granular soils and decreases for fine-grained soils. The value of MR is highly stress dependent, with the stress state (i.e., bulk stress) a function of the position of the materials in the pavement structure and applied traffic loading. Applying excessive vertical stress at the top of the subgrade without knowing the appropriate stress state can result in permanent deformation. In situ stress must be calculated so the correct resilient modulus can be determined. To facilitate the implementation of MEPDG, this study develops a methodology to select the appropriate subgrade resilient modulus for predicting rutting and IRI. A comprehensive research methodology was undertaken to study the effect of in situ or undisturbed subgrade MR on pavement performance using the MEPDG. Results show that MR obtained from in situ stress is approximately 1.4 times higher than the MR estimate from NCHRP-285. Thus, the in situ stress significantly affects the calculation of subgrade MR and, subsequently, the use of MR in the predicted rutting, with IRI using the AASHTOWare pavement mechanistic-empirical design. Results also show that the pavement sections were classified as in “Good” and “Fair” conditions for rutting and IRI, respectively, considering in situ MR.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"11 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87960088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-17DOI: 10.3390/geotechnics3020022
Behzad Dastjerdy, A. Saeidi, Shahriyar Heidarzadeh
The reliability of geomechanical models and engineering designs depend heavily on high-quality data. In geomechanical projects, collecting and analyzing laboratory data is crucial in characterizing the mechanical properties of soils and rocks. However, insufficient lab data or underestimating data treatment can lead to unreliable data being used in the design stage, causing safety hazards, delays, or failures. Hence, detecting outliers or extreme values is significant for ensuring accurate geomechanical analysis. This study reviews and categorizes applicable outlier detection methods for geomechanical data into fence labeling methods and statistical tests. Using real geomechanical data, the applicability of these methods was examined based on four elements: data distribution, sensitivity to extreme values, sample size, and data skewness. The results indicated that statistical tests were less effective than fence labeling methods in detecting outliers in geomechanical data due to limitations in handling skewed data and small sample sizes. Thus, the best outlier detection method should consider this matter. Fence labeling methods, specifically, the medcouple boxplot and semi-interquartile range rule, were identified as the most accurate outlier detection methods for geomechanical data but may necessitate more advanced statistical techniques. Moreover, Tukey’s boxplot was found unsuitable for geomechanical data due to negative confidence intervals that conflicted with geomechanical principles.
{"title":"Review of Applicable Outlier Detection Methods to Treat Geomechanical Data","authors":"Behzad Dastjerdy, A. Saeidi, Shahriyar Heidarzadeh","doi":"10.3390/geotechnics3020022","DOIUrl":"https://doi.org/10.3390/geotechnics3020022","url":null,"abstract":"The reliability of geomechanical models and engineering designs depend heavily on high-quality data. In geomechanical projects, collecting and analyzing laboratory data is crucial in characterizing the mechanical properties of soils and rocks. However, insufficient lab data or underestimating data treatment can lead to unreliable data being used in the design stage, causing safety hazards, delays, or failures. Hence, detecting outliers or extreme values is significant for ensuring accurate geomechanical analysis. This study reviews and categorizes applicable outlier detection methods for geomechanical data into fence labeling methods and statistical tests. Using real geomechanical data, the applicability of these methods was examined based on four elements: data distribution, sensitivity to extreme values, sample size, and data skewness. The results indicated that statistical tests were less effective than fence labeling methods in detecting outliers in geomechanical data due to limitations in handling skewed data and small sample sizes. Thus, the best outlier detection method should consider this matter. Fence labeling methods, specifically, the medcouple boxplot and semi-interquartile range rule, were identified as the most accurate outlier detection methods for geomechanical data but may necessitate more advanced statistical techniques. Moreover, Tukey’s boxplot was found unsuitable for geomechanical data due to negative confidence intervals that conflicted with geomechanical principles.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"29 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82038347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-15DOI: 10.3390/geotechnics3020020
Diwakar KC, Liangbo Hu
Wildfires have a strong influence on various geotechnical and hydraulic properties of soils and sediments, which may become more vulnerable to landslides or debris flows. In the present study, a case investigation of the 2018 post-wildfire debris flows in Montecito, California, USA, was conducted, with a focus on the wildfire-affected areas and debris volume estimation. Significant debris were deposited around four major creeks, i.e., Montecito Creek, San Ysidro Creek, Buena Vista Creek, and Romero Creek in January, 2018, one month after the Thomas fire. Satellite images utilizing remote sensing techniques and geographic information system (GIS) data were analyzed to identify areas affected by the wildfire. Relevant data, including the slope, catchment area, and rainfall were used in two empirical models to estimate the debris volumes around the four creeks. As compared with field observation, each debris volume estimated with these empirical models was within the same order of magnitude. The debris volumes were generally underestimated when using the rainfall recorded at the Montecito Weather Station; the estimates considerably improved with the rainfall record from the Doulton Tunnel Station. The results showed that, overall, such empirical approaches are still of benefit for engineering practice, as they are capable of offering first-order approximations. The accuracy and availability of rainfall data are critical factors; the rainfall data in mountainous areas are generally higher than in the low lands, and consequently were more suitable for debris volume estimation in the present study, where the debris flows typically occurred in areas with steep slopes and at higher elevations.
{"title":"Post-Wildfire Debris Flows in Montecito, California (USA): A Case Study and Empirically Based Debris Volume Estimation","authors":"Diwakar KC, Liangbo Hu","doi":"10.3390/geotechnics3020020","DOIUrl":"https://doi.org/10.3390/geotechnics3020020","url":null,"abstract":"Wildfires have a strong influence on various geotechnical and hydraulic properties of soils and sediments, which may become more vulnerable to landslides or debris flows. In the present study, a case investigation of the 2018 post-wildfire debris flows in Montecito, California, USA, was conducted, with a focus on the wildfire-affected areas and debris volume estimation. Significant debris were deposited around four major creeks, i.e., Montecito Creek, San Ysidro Creek, Buena Vista Creek, and Romero Creek in January, 2018, one month after the Thomas fire. Satellite images utilizing remote sensing techniques and geographic information system (GIS) data were analyzed to identify areas affected by the wildfire. Relevant data, including the slope, catchment area, and rainfall were used in two empirical models to estimate the debris volumes around the four creeks. As compared with field observation, each debris volume estimated with these empirical models was within the same order of magnitude. The debris volumes were generally underestimated when using the rainfall recorded at the Montecito Weather Station; the estimates considerably improved with the rainfall record from the Doulton Tunnel Station. The results showed that, overall, such empirical approaches are still of benefit for engineering practice, as they are capable of offering first-order approximations. The accuracy and availability of rainfall data are critical factors; the rainfall data in mountainous areas are generally higher than in the low lands, and consequently were more suitable for debris volume estimation in the present study, where the debris flows typically occurred in areas with steep slopes and at higher elevations.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"79 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81341453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the present research, a comprehensive experimental investigation was carried out for the geotechnical characterisation of new synthetic lightweight aggregates (SLAs) composed of reused biomass fly ash and waste plastics (i.e. high-density and low-density polyethylene, i.e. HDPE and LDPE). Aggregate fly ash-to-plastic ratio, by weight, was 50:50. Both aggregates were characterised by low specific gravity values, i.e. 0.98. The physical, chemical and mechanical properties (i.e. one-dimensional compressibility, creep properties, compaction features and stress-strain-strength behavior) of lightweight aggregates were evaluated together with hydraulic conductivity and water absorbability. Based on one-dimensional compression test results, lightweight aggregates made of fly ash and HDPE resulted to be less compressible upon loading compared to the companion material made of fly ash and LDPE and exhibited an overall response similar to that of traditional aggregates of expanded clay. Moreover, the analysis of the time-dependent compressive behavior of the two synthetic lightweight aggregates showed that the creep rate depends on applied stress in the range of 50 kPa to 400 kPa with values of creep coefficients C αε slightly higher than those of compacted sand, but comparable, or even lower, than those of other recycled materials. Shear strength parameters, including peak friction angle (ϕ′) and cohesion intercept (c′), determined by isotropically consolidated drained triaxial compression tests, were very satisfactory for both aggregates. The ϕ′ is within the range of 42.3 to 46.3°, and c′ is in the range of 1.3 to 8.6 kPa, with the highest values concerning the fly ash-HDPE aggregate. Constant head permeability tests provided values of the hydraulic conductivity (k)in the range 3÷4·10−4 m/s evidencing favourable permeability properties of both investigated synthetic aggregates. Leaching tests and thermal stability analyses proved the sustainability of both aggregates from an environmental point of view. Finally, the results obtained in the present study demonstrate the suitability of the investigated lightweight synthetic aggregates for valuable use in many geotechnical applications.
{"title":"Environmental and geotechnical properties of lightweight aggregates made of reused solid wastes","authors":"D. Porcino, G. Tomasello, F. Mauriello, A. Malara","doi":"10.1680/jenge.22.00077","DOIUrl":"https://doi.org/10.1680/jenge.22.00077","url":null,"abstract":"In the present research, a comprehensive experimental investigation was carried out for the geotechnical characterisation of new synthetic lightweight aggregates (SLAs) composed of reused biomass fly ash and waste plastics (i.e. high-density and low-density polyethylene, i.e. HDPE and LDPE). Aggregate fly ash-to-plastic ratio, by weight, was 50:50. Both aggregates were characterised by low specific gravity values, i.e. 0.98. The physical, chemical and mechanical properties (i.e. one-dimensional compressibility, creep properties, compaction features and stress-strain-strength behavior) of lightweight aggregates were evaluated together with hydraulic conductivity and water absorbability. Based on one-dimensional compression test results, lightweight aggregates made of fly ash and HDPE resulted to be less compressible upon loading compared to the companion material made of fly ash and LDPE and exhibited an overall response similar to that of traditional aggregates of expanded clay. Moreover, the analysis of the time-dependent compressive behavior of the two synthetic lightweight aggregates showed that the creep rate depends on applied stress in the range of 50 kPa to 400 kPa with values of creep coefficients C αε slightly higher than those of compacted sand, but comparable, or even lower, than those of other recycled materials. Shear strength parameters, including peak friction angle (ϕ′) and cohesion intercept (c′), determined by isotropically consolidated drained triaxial compression tests, were very satisfactory for both aggregates. The ϕ′ is within the range of 42.3 to 46.3°, and c′ is in the range of 1.3 to 8.6 kPa, with the highest values concerning the fly ash-HDPE aggregate. Constant head permeability tests provided values of the hydraulic conductivity (k)in the range 3÷4·10−4 m/s evidencing favourable permeability properties of both investigated synthetic aggregates. Leaching tests and thermal stability analyses proved the sustainability of both aggregates from an environmental point of view. Finally, the results obtained in the present study demonstrate the suitability of the investigated lightweight synthetic aggregates for valuable use in many geotechnical applications.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46255687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-06DOI: 10.3390/geotechnics3020019
Yu Wang, Rolando P Orense
Inclined piles have been widely applied as one of the countermeasures against large lateral spreading induced by soil liquefaction during earthquakes. However, the unsatisfactory performance of inclined piles in past events has impeded their application in seismic areas. To elucidate the performance of inclined piles when subjected to lateral spreading induced by soil liquefaction, numerical analyzes were performed using the OpenSees framework. For this purpose, a comprehensive three-dimensional finite element model was developed. Interface elements were used between the soil and the pile to account for the friction and gapping mechanisms. A multi-yield-surface plasticity constitutive relationship for sand was adopted to simulate the soil liquefaction behavior. Based on the proposed numerical model, parametric analyzes were conducted to investigate the influence of various factors on the behavior of inclined piles, including the raked angle of the pile, the ground slope, the soil profile, and the amplitude of the input motion. The response of the system indicates that inclined piles can behave better than vertical piles in decreasing soil deformation and the cap response. The influences of the investigated factors are highlighted to adopt the appropriate pile inclination in laterally spreading ground and maximize the advantages of using inclined piles.
{"title":"Numerical Investigation of Inclined Piles under Liquefaction-Induced Lateral Spreading","authors":"Yu Wang, Rolando P Orense","doi":"10.3390/geotechnics3020019","DOIUrl":"https://doi.org/10.3390/geotechnics3020019","url":null,"abstract":"Inclined piles have been widely applied as one of the countermeasures against large lateral spreading induced by soil liquefaction during earthquakes. However, the unsatisfactory performance of inclined piles in past events has impeded their application in seismic areas. To elucidate the performance of inclined piles when subjected to lateral spreading induced by soil liquefaction, numerical analyzes were performed using the OpenSees framework. For this purpose, a comprehensive three-dimensional finite element model was developed. Interface elements were used between the soil and the pile to account for the friction and gapping mechanisms. A multi-yield-surface plasticity constitutive relationship for sand was adopted to simulate the soil liquefaction behavior. Based on the proposed numerical model, parametric analyzes were conducted to investigate the influence of various factors on the behavior of inclined piles, including the raked angle of the pile, the ground slope, the soil profile, and the amplitude of the input motion. The response of the system indicates that inclined piles can behave better than vertical piles in decreasing soil deformation and the cap response. The influences of the investigated factors are highlighted to adopt the appropriate pile inclination in laterally spreading ground and maximize the advantages of using inclined piles.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"214 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75758155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-05DOI: 10.3390/geotechnics3020017
A. Yerro, F. Ceccato
Interactions between soil, fluids (e.g., water), and structures are intrinsic to most geotechnical problems. However, these can be extremely complex and further understanding is needed in this field. Soil–water–structure interactions can be studied on many different scales (micro to macro) and perspectives (experimental, numerical, and theoretical). In any case, the consequences of these interactions control soil behaviour, the stability of civil infrastructure, and, ultimately, the safety of our communities. This Special Issue consists of five papers (three research papers and two literature reviews) that highlight the importance of soil–water–structure interactions in a broad range of different applications. The topics addressed in the research contributions include (a) the performance of shallow footings under oblique loads, (b) the assessment of nonlinear base-isolated building systems under dynamic loading, and (c) the applicability of lightweight materials as fill for retaining wall systems. The other innovative papers, on the other hand, provide comprehensive reviews on (d) the role of the clay content in the interface characteristics between sand–clay mixtures and structures and (e) the latest developments in the understanding and measurements of the Atterberg limits.
{"title":"Soil–Water–Structure Interactions","authors":"A. Yerro, F. Ceccato","doi":"10.3390/geotechnics3020017","DOIUrl":"https://doi.org/10.3390/geotechnics3020017","url":null,"abstract":"Interactions between soil, fluids (e.g., water), and structures are intrinsic to most geotechnical problems. However, these can be extremely complex and further understanding is needed in this field. Soil–water–structure interactions can be studied on many different scales (micro to macro) and perspectives (experimental, numerical, and theoretical). In any case, the consequences of these interactions control soil behaviour, the stability of civil infrastructure, and, ultimately, the safety of our communities. This Special Issue consists of five papers (three research papers and two literature reviews) that highlight the importance of soil–water–structure interactions in a broad range of different applications. The topics addressed in the research contributions include (a) the performance of shallow footings under oblique loads, (b) the assessment of nonlinear base-isolated building systems under dynamic loading, and (c) the applicability of lightweight materials as fill for retaining wall systems. The other innovative papers, on the other hand, provide comprehensive reviews on (d) the role of the clay content in the interface characteristics between sand–clay mixtures and structures and (e) the latest developments in the understanding and measurements of the Atterberg limits.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"33 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91329040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-05DOI: 10.3390/geotechnics3020018
Chun-Hsing Ho, Jeremy DeGeyter, Dada Zhang
This paper provides a five-year performance evaluation of an application of geogrid reinforcement in low-volume unpaved roads using dynamic cone penetrometer (DCP), plate load tests (PLT), and roadway sensing method. A Forest Service unpaved road located in northern Arizona, USA, exhibited severe deterioration on the surface, creating an unsafe traffic environment for vehicles. A total of four structural sections (1–4; 4.3 m wide) were installed in the 40 m long test area. One additional section of existing subgrade/roadbed with native soil adjacent to the test sections was used for comparison purposes. The project was originally completed in November 2015, followed by five annual field visits to observe surface conditions of the five test sections. Based on DCP and PLT results (both conducted in 2015), and roadway sensing tests conducted in 2020, the section made of 30 cm thick aggregate with one geogrid layer appeared to have a better capacity for resisting traffic loading as compared with the other four sections. This paper concludes that, from a long-term point of view, the geogrid reinforcement improves the capacity of the unpaved roads, with significantly reduced rutting and damage from both roadway traffic loads and weathering effects.
{"title":"Five-Year Performance Evaluation of Geogrid Reinforcement in Low-Volume Unpaved Roads Using Dynamic Cone Penetrometer, Plate Load Test and Roadway Sensing","authors":"Chun-Hsing Ho, Jeremy DeGeyter, Dada Zhang","doi":"10.3390/geotechnics3020018","DOIUrl":"https://doi.org/10.3390/geotechnics3020018","url":null,"abstract":"This paper provides a five-year performance evaluation of an application of geogrid reinforcement in low-volume unpaved roads using dynamic cone penetrometer (DCP), plate load tests (PLT), and roadway sensing method. A Forest Service unpaved road located in northern Arizona, USA, exhibited severe deterioration on the surface, creating an unsafe traffic environment for vehicles. A total of four structural sections (1–4; 4.3 m wide) were installed in the 40 m long test area. One additional section of existing subgrade/roadbed with native soil adjacent to the test sections was used for comparison purposes. The project was originally completed in November 2015, followed by five annual field visits to observe surface conditions of the five test sections. Based on DCP and PLT results (both conducted in 2015), and roadway sensing tests conducted in 2020, the section made of 30 cm thick aggregate with one geogrid layer appeared to have a better capacity for resisting traffic loading as compared with the other four sections. This paper concludes that, from a long-term point of view, the geogrid reinforcement improves the capacity of the unpaved roads, with significantly reduced rutting and damage from both roadway traffic loads and weathering effects.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"136 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79629692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
FengYongchang, ChenLin, MereySukru, LijithKoorthedath Pullayikodi, SinghDevendra N, KomiyaAtsuki, MaruyamaShigenao
Gas hydrates are regarded as one of the most promising alternative sources of energy, which have the potential to address the energy demand of a contemporary society. Based on the field explorations in the Eastern Nankai Trough (Japan), a multilayered hydrate reservoir model has been conceptualised and its behaviours during depressurisation production are simulated. This model incorporates the effects of the initial reservoir temperature and permeability on the mechanism of hydrate dissociation, which in turn affects the gas production. It is shown that the dissociation process is largely affected by the initial temperature distribution within the reservoir layers, and the ‘warmer’ reservoirs show (consistently) higher production potential. Furthermore, the gas production could be improved significantly, by increasing the permeability of the wellbore region, which can be achieved through the fracturing process. The close match between the simulation results and the field tests is noteworthy. The proposed multilayered model would be quite useful for analysing the efficacy of the ‘production strategy’, in most real-life situations.
{"title":"Simulation of gas production from hydrate reservoirs (AT1) of Eastern Nankai Trough, Japan","authors":"FengYongchang, ChenLin, MereySukru, LijithKoorthedath Pullayikodi, SinghDevendra N, KomiyaAtsuki, MaruyamaShigenao","doi":"10.1680/jenge.19.00177","DOIUrl":"https://doi.org/10.1680/jenge.19.00177","url":null,"abstract":"Gas hydrates are regarded as one of the most promising alternative sources of energy, which have the potential to address the energy demand of a contemporary society. Based on the field explorations in the Eastern Nankai Trough (Japan), a multilayered hydrate reservoir model has been conceptualised and its behaviours during depressurisation production are simulated. This model incorporates the effects of the initial reservoir temperature and permeability on the mechanism of hydrate dissociation, which in turn affects the gas production. It is shown that the dissociation process is largely affected by the initial temperature distribution within the reservoir layers, and the ‘warmer’ reservoirs show (consistently) higher production potential. Furthermore, the gas production could be improved significantly, by increasing the permeability of the wellbore region, which can be achieved through the fracturing process. The close match between the simulation results and the field tests is noteworthy. The proposed multilayered model would be quite useful for analysing the efficacy of the ‘production strategy’, in most real-life situations.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135399702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-30DOI: 10.3390/geotechnics3020016
Ashley P. Dyson, Ali Tolooiyan, D. V. Griffiths
It is well recognised that plant vegetation and roots are capable of improving the shear strength of hillslopes by reinforcing soil shear resistance. Several key factors influencing the level of slope reinforcement include root geometry, orientation and strength. To assess the mechanical performance of vegetated slopes using numerical methods, root structures can be represented by beam and pile elements to mirror root behaviour. In contrast, root reinforcement can be modelled indirectly through a root cohesion factor, supplying additional strength to the soil surrounding the root zone. In this paper, correlations between these two numerical methods are presented, highlighting the applicability of each technique based on various root characteristics. Three types of root geometries are presented, consisting of a primary tap root, a secondary cohesion zone surrounding the main root and a root branching process. The results of the finite element analysis demonstrate the variation in the slope factor of safety for both methods, with a set of correlations between the two modelling approaches. A series of stability charts are presented for each method, quantifying the effects of root characteristics on slope reinforcement.
{"title":"Numerical Modelling Techniques for Stability Analysis of Slopes Reinforced with Shallow Roots","authors":"Ashley P. Dyson, Ali Tolooiyan, D. V. Griffiths","doi":"10.3390/geotechnics3020016","DOIUrl":"https://doi.org/10.3390/geotechnics3020016","url":null,"abstract":"It is well recognised that plant vegetation and roots are capable of improving the shear strength of hillslopes by reinforcing soil shear resistance. Several key factors influencing the level of slope reinforcement include root geometry, orientation and strength. To assess the mechanical performance of vegetated slopes using numerical methods, root structures can be represented by beam and pile elements to mirror root behaviour. In contrast, root reinforcement can be modelled indirectly through a root cohesion factor, supplying additional strength to the soil surrounding the root zone. In this paper, correlations between these two numerical methods are presented, highlighting the applicability of each technique based on various root characteristics. Three types of root geometries are presented, consisting of a primary tap root, a secondary cohesion zone surrounding the main root and a root branching process. The results of the finite element analysis demonstrate the variation in the slope factor of safety for both methods, with a set of correlations between the two modelling approaches. A series of stability charts are presented for each method, quantifying the effects of root characteristics on slope reinforcement.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135564011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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