Seismic response of a mid-story isolated structure considering SSI in mountainous areas under long-period earthquakes

At present,there is not much research on mid-story isolated structures in mountainous areas.In this study,a model of a mid-story isolated structure considering soil-structure interaction(SSI)in mountainous areas is established along with a model that does not consider SSI.Eight long-period earthquake waves and two ordinary earthquake waves are selected as inputs for the dynamic time history analysis of the structure.The results show that the seismic response of a mid-story isolated structure considering SSI in mountainous areas can be amplified when compared with a structure that does not consider SSI.The structure response under long-period earthquakes is larger than that of ordinary earthquakes.The structure response under far-field harmonic-like earthquakes is larger than that of near-fault pulse-type earthquakes.The structure response under near-fault pulse-type earthquakes is larger than that of far-field non-harmonic earthquakes.When subjected to long-period earthquakes,the displacement of the isolated bearings exceeded the limit value,which led to instability and overturning of the structure.The structure with dampers in the isolated story could adequately control the nonlinear response of the structure,effectively reduce the displacement of the isolated bearings,and provide a convenient,efficient and economic method not only for new construction but also to retrofit existing structures.

Responses of Nutrients to the Precipitation Variation and Land Use in Subtropical Monsoonal Small Mountainous Rivers:A Case Study of Baixi Watershed

Small mountainous rivers are characterized by large instantaneous fluxes and susceptible to extreme weather events,which can rapidly transport materials into the sea and have a significant impact on the ecological environment of estuaries and bays.In order to investigate the seasonal characteristics of nutrients in small mountainous rivers in the subtropical monsoon region and the output pattern to the sea during heavy precipitation,surveys on the mountainous rivers were carried out in Baixi watershed in August 2020(wet season),March 2021(dry season)and June 2021(Meiyu period).The results showed that the dissolved inorganic nitrogen(DIN)of the rivers has an average concentration of 752μg L^(−1)in the wet season and 1472μg L^(−1)in the dry season.The concentrations of dissolved inorganic phosphorus(DIP)in wet season and dry season were 63μg L^(−1)and 51μg L^(−1),respectively.Influenced by the changes of land use in sub-watersheds,DIN concentrations in the mainstream increased from 701μg L^(−1)in the upper reaches to 1284μg L^(−1)in the middle reaches.Two rainstorms during the Meiyu period in the watershed caused the pulse runoff in the river.The maximum daily runoff reached 70 times that before rains.The maximum daily fluxes of DIN and DIP were 109 and 247 times that before rains,respectively.In view that the watershed experienced several rainstorms in the wet season,the river,with pulse runoff,carries a large amount of nutrients into the sea in a short time,which will have a significant impact on the environment of Sanmen bay and its adjacent sea.

Impact of typical environments in China’s western mountainous areas on the durability of railway concrete:a review

Purpose–This study aims to analyze the impact mechanism of typical environments in China’s western mountainous areas on the durability of railway concrete and propose measures to improve durability.Design/methodology/approach–With the continuous promotion of infrastructure construction,the focus of China’s railway construction has gradually shifted to the western region.The four typical environments of large temperature differences,strong winds and dryness,high cold and low air pressure unique to the western mountainous areas of China have adverse effects on the durability of typical railway structure concrete(bridges,ballastless tracks and tunnels).This study identified the characteristics of four typical environments in the western mountainous areas of China through on-site research.The impact mechanism of the four typical environments on the durability of concrete in different structural parts of railways has been explored through theoretical analysis and experimental research;Finally,a strategy for improving the durability of railway concrete suitable for the western mountainous areas of China was proposed.Findings–The daily temperature difference in the western mountainous areas of China is more than twice that of the plain region,which will lead to significant temperature deformation and stress in the multi-layered structure of railway ballastless tracks.It will result in cracking.The wind speed in the western plateau region is about 2.5 to 3 times that of the plain region,and the average annual rainfall is only 1/5 of that in the plain region.The drying effect on the surface of casting concrete will significantly accelerate its cracking process,leading to serious durability problems.The environmental temperature in the western mountainous areas of China is generally low,and there are more freeze-thaw cycles,which will increase the risk of freeze-thaw damage to railway concrete.The environmental air pressure in the western plateau region is only 60%of that in the plain region.The moisture inside the concrete is more likely to diffuse into the surrounding environment under the pressure difference,resulting in greater water loss and shrinkage deformation of the concrete in the plateau region.The above four issues will collectively lead to the rapid deterioration of concrete durability in the western plateau region.The corresponding durability improvement suggestions from theoretical research,new technology development and standard system was proposed in this paper.Originality/value–The research can provide the mechanism of durability degradation of railway concrete in the western mountainous areas of China and corresponding improvement strategies.

CFD Investigation of Diffusion Law and Harmful Boundary of Buried Natural Gas Pipeline in the Mountainous Environment

The leakage gas from a buried natural gas pipelines has the great potential to cause economic losses and environmental pollution owing to the complexity of the mountainous environment.In this study,computational fluid dynamics(CFD)method was applied to investigate the diffusion law and hazard range of buried natural gas pipeline leakage in mountainous environment.Based on cloud chart,concentration at the monitoring site and hazard range of lower explosion limit(LEL)and upper explosion limit(UEL),the influences of leakage hole direction and shape,soil property,burial depth,obstacle type on the diffusion law and hazard range are analyzed.Results show that the leakage gas is not radially diffused until it reaches the ground,and the velocity of gas diffusion to the ground and the hazard range decrease as the angle between the leaking direction and the buoyancy direction increases.Triangular and square leak holes have a faster diffusion rate and a wider hazard range than circular.The diffusion rate of leakage gas in soil rises as soil granularity and porosity increase.The time of leakage gas diffusion to the ground increases significantly with the increase of burial depth,and the hazard range reduces as burial depth increases.Boulder-type obstacles will alter the diffusion path of the leakage gas and accelerate the expansion of the hazard distance,while trench-type obstacles will cause the natural gas to accumulate in the trench and form a high concentration region slowing the expansion of the surface gas concentration.

Understanding and simulating of three-dimensional subsurface hydrological partitioning in an alpine mountainous area, China

Critical zone(CZ)plays a vital role in sustaining biodiversity and humanity.However,flux quantification within CZ,particularly in terms of subsurface hydrological partitioning,remains a significant challenge.This study focused on quantifying subsurface hydrological partitioning,specifically in an alpine mountainous area,and highlighted the important role of lateral flow during this process.Precipitation was usually classified as two parts into the soil:increased soil water content(SWC)and lateral flow out of the soil pit.It was found that 65%–88%precipitation contributed to lateral flow.The second common partitioning class showed an increase in SWC caused by both precipitation and lateral flow into the soil pit.In this case,lateral flow contributed to the SWC increase ranging from 43%to 74%,which was notably larger than the SWC increase caused by precipitation.On alpine meadows,lateral flow from the soil pit occurred when the shallow soil was wetter than the field capacity.This result highlighted the need for three-dimensional simulation between soil layers in Earth system models(ESMs).During evapotranspiration process,significant differences were observed in the classification of subsurface hydrological partitioning among different vegetation types.Due to tangled and aggregated fine roots in the surface soil on alpine meadows,the majority of subsurface responses involved lateral flow,which provided 98%–100%of evapotranspiration(ET).On grassland,there was a high probability(0.87),which ET was entirely provided by lateral flow.The main reason for underestimating transpiration through soil water dynamics in previous research was the neglect of lateral root water uptake.Furthermore,there was a probability of 0.12,which ET was entirely provided by SWC decrease on grassland.In this case,there was a high probability(0.98)that soil water responses only occurred at layer 2(10–20 cm),because grass roots mainly distributed in this soil layer,and grasses often used their deep roots for water uptake during ET.To improve the estimation of soil water dynamics and ET,we established a random forest(RF)model to simulate lateral flow and then corrected the community land model(CLM).RF model demonstrated good performance and led to significant improvements in CLM simulation.These findings enhance our understanding of subsurface hydrological partitioning and emphasize the importance of considering lateral flow in ESMs and hydrological research.

Spatio-temporal Evolution and Optimization of Landscape Ecological Risk in Karst Mountainous Areas

[Objective]The ecological vulnerability and landscape ecological risk of karst mountainous areas have increased as a result of enhanced disturbance of natural resources by human activities.This paper aimed to explore the characteristics of ecological risk evolution under different landscape patterns in the region,with a view to providing reference for land classification protection,sustainable use of resources and regional ecological risk optimization in karst mountainous areas.[Method]Taking Huangping County,a typical karst mountainous area,as an example,eight evaluation factors of natural and landscape patterns were selected to construct a landscape ecological risk evaluation model,to quantitatively explore the spatio-temporal evolution of landscape ecological risk and the trend of risk level transfer in the study area from^(2)010-2018,and to reveal the complex relationship between ecological risk and topography in karst mountainous areas.[Result]①From 2010 to 2018,land use types changed to different degrees,with the most amount of woodland transferred out(1627.37 hm^(2))and the most amount of construction land transferred in(1303.93 hm^(2));a total of 3552.31 hm^(2) of land was transferred,with a change ratio of 2.13%,and there was a significant conversion between construction land,arable land,and woodland.②From 2010 to 2018,the landscape ecological risk in the study area changed significantly,and the landscape ecological risk index decreased from 0.3441 to 0.1733,showing an upward and then downward trend;the landscape ecological risk of the whole region was dominated by low-risk and lower-risk zones,and the ecological risk level generally shifted from a high level to a low level,and the ecological environment was improved.③There was a negative correlation between ecological risk and topographic position,and high-risk zones were mainly distributed among low topographic zones;with the change of time,the advantage of risk level for the selection of topography was gradually weakened,and the influence of anthropogenic factors on the ecological risk of the landscape was becoming more and more prominent.[Conclusion]This paper can provide theoretical basis for land use optimization and ecological protection in karst mountainous areas.

Settlement Control Standards of Construction and Expansion for Mountainous Highway Roadbeds

This article analyzes the differential settlement of new and old roadbeds after widening and its characteristics based on a highway reconstruction and expansion project case study.The research proposes a subgrade settlement control standard that states that the maximum differential settlement value should be less than 5 cm when the embankment fill height exceeds 20 m.Similarly,the maximum differential settlement value should be less than 10 cm when the embankment fill height does not exceed 20 m.The findings of the study can provide a useful reference for the design of roadbed widening in highway reconstruction and expansion projects.

Loading Stress Analysis of Cement Concrete Pavement in Mountainous Areas

The suitable cement concrete pavement for mountainous areas is a form of low-cost cement concrete pavement that uses unconventional graded stones in different proportions in ordinary concrete,allowing the concrete to fully contact the stones and form a stable and well-bonded slab with large particle stones.As large particle stones replace a certain volume of cement concrete,they have good economic performance and are a low-cost form of cement concrete pavement.This study researches the use of ANSYS tools to analyze the influence of geometric dimensions and material properties of rigid pavement structural layers on the mechanical properties of pavement structures.

On the Ecological Restoration Modes of Rocky Desertification in Chongqing Zhongliang Mountainous Area

In the Haishi Park Demonstration Base of Zhongliang Mountain in Chongqing, ecological restoration modes were established based on growth status of local plants and other natural environmental conditions, including forestry ecology, tourism ecology, agricultural ecology as well as the combined mode of various ecological types.

Planning and Design of Sightseeing Agricultural Park Characterized by Mountainous Landscape

After illustration of research and development process of sightseeing agricultural park,the paper had classified sightseeing agricultural park into sightseeing agricultural park,education agricultural park and agricultural garden in terms of development content;into renovation type and newly-built type in accordance with development mode;and into plain type and mountainous type in the light of terrain.From the perspectives of terrain,vegetation,hydrology and ecology,characteristics of landscape resources in mountainous sightseeing agricultural park were analyzed.It proposed principles for planning and design of mountainous sightseeing agricultural park,which were respecting and protecting nature,linking landscape units and coordinating spatial structure,systematicness and protecting inheritance of traditional culture.On this basis,it had illustrated landscape designing theories on architecture and landscape furniture,traffic road,plant greening and water supply and sewerage works.

Ecological Carrying Capacity in Beijing Mountainous Areas——Taking Fangshan District as an Example

[Objective] The aim was to investigate ecological carrying capacity of Fangshan District in Beijing. [Method] Ecological footprint and carrying capacity of Fangshan District in 2007 and 2008 were analyzed with ecological footprint model and the difference between ecological footprint and carrying capacity there was con- cluded. Furthermore, an assessment was made on relation between Fangshan de- velopment with local ecological carrying capacity to evaluate sustainable development of Fangshan District. [Result] Fangshan District is of lightly ecological deficit; ecologi- cal footprint per capita in 2007-2008 was deficit and tended to expand. Two meth- ods are available to reduce ecological ：deficit, including reduction of ecological foot- print and increase of carrying capacity. In general, supply and demand of carrying capacity in Fangshan are better, though with some problems. It is necessary to fur- ther develop related industries to final eliminate ecological deficit in order to achieve ecological conservation-orientation and sustainable development of Fangshan District. [Conclusion] The research provides theoretical references for overall evaluation on eco- logical carrying capacity of Fangshan District.

Planning and Design of Mountainous Agricultural Sightseeing Garden——a Case Study of Ruimin Agricultural Sightseeing Eco-garden

Agricultural sightseeing project is expanding with social development, yet most are confined in improvements in original gardens, with similar style or pattern. The research took Uupanshui City as an example and analyzed mountain-based ag- ricultural sightseeing in order to discuss the way to propel agriculture integration with leisure tourism, processing, establish new models for sightseeing eco-garden gardens, and benefit economically, socially and ecologically.

Study on Urban Construction Land Suitability Evaluation in Southwestern Mountainous Areas of Yunnan Province Based on the Strategy of "Protecting Farmland in Flatland Areas and Constructing Mountainous Cities" : A Case in Lianghe County

According to the particularity of towns＇ construction in the southwestern mountainous areas of Yunnan Province, this study has built constructive land suit- ability evaluation index system which is different to flat area. Then this study deter- mined single evaluation factors index and comprehensive suitability index using ＂ex- treme conditions method＂ and ＂suitability index method＂, and analyzed and assessed the constructive land suitability on each evaluation unit polygons and its suitability level by using GIS software. Taking Lianghe County of Dehong Dai-Jingpo Au- tonomous Prefecture as an example to evaluate land suitability in Lianghe County＇s main towns around the gentle slope, the results show, in the evaluation area, the area of land suitable for construction and unsuitable for construction respectively ac- count 73.58% and 26.42%. And first-class, second and third-class of land suitable for construction should be composited at the ratio of about 11：49：40. The suitability evaluation index system and method developed in this paper is applicable for evalu- ating the construction land suitability in mountainous areas of southwest Yunnan Province, and will provide theoretical and technical support for land policy measures which strengthen the protection of farmland and promote the scientific development of urbanization in Yunnan Province and even similar mountainous areas of the whole China.

Eco-tourism: A New Approach of Ecological Rehabilitation and Out of Poverty Development in Wumeng Mountainous Area

The economic and social development status and the formation mechanism of "poverty trap" in Wumeng mountainous area were analyzed, the feasibility of developing eco-tourism to ecological restoration and rural poverty reduction was discussed, and some corresponding countermeasures were put forward.

Research on the Value of Chinese Famous Mountainous Scenic Spots in the Perspective of Cultural Landscape

After summarizing relevant researches on famous mountainous scenic spots and the development of cultural landscapes in world cultural heritages, the paper has analyzed the value of famous mountainous scenic spots in China and considered that Chinese famous mountainous scenic spots are of rich natural science value and unique aesthetic value, have inherited traditional humane landscape aesthetic value, reflected the philosophical view of "the unity between heaven and human" and profound religious culture, and preserved rich cultural remains, corresponding with the definition and requirement of cultural landscape in world heritages.

Application of Wild Plant Resources of Qin-ba Mountainous Area for Vertical vrescence in Landscape Architecture

Based on introducing wild plant resources of vertical greening in Qin-ba Mountainous area, the application of vertical greening plants of Qin-ba Mountainous area in garden greening were analyzed, the measures of utilization and development were suggested.

Eco-tourism Development Conception of Wutai Mountainous Scenic Area in Shanxi Province

From the perspectives of sustainable development and creating high-quality tourism brand,this study proposed the scheme of establishing two particular eco-tourism routes based on the characteristics of tourist resources and present tourism development in Wutai Mountainous Scenic Area.The conception of eco-tourism would be able to integrate typical and unique temple landscapes and geological heritages in the study area,in this way to create high-quality tourism brands,make the travel more scientific and interesting,and give it higher ornamental and cultural value.

Analysis on the Green Space System Planning of Small Cities in Mountainous Areas

With the urban green space system planning of small cities in mountainous areas as the study object,the planning practices are analyzed and studied to summarize the common characteristics of urban green space system planning in those small cities.Being combined with relevant national standards and regulations,the problems that those small cities are faced with in their urban green space system planning are analyzed,then corresponding countermeasures and suggestions are put forward to resolve problems in the practical planning.

Plant Planning of Eco-park in Mountainous Regions

By studying the planning of Aoshan Park in Jianyang City,a typical eco-park in mountainous regions,the authors analyzed its topography and vegetations,specifically,vegetation types and plant species,and pointed out problems of its present vegetations based on the evaluation.By maintaining existing indigenous plant species,plant planning and ecological corridor design was carried out to rebuild the eco-forest belt of Mt.Aoshan and optimize landscapes in Aoshan Park.Plant landscaping of Aoshan Park,by following the principles of "ecological" and "right trees for right land",has 3 different styles:natural,regular and mixed.Regular style is mainly located in the cultural experience area by applying regular planting types,such as coupled planting and mass planting;natural style runs through the park from north to south,and takes seasonal changes of landscapes as the theme to show the attraction of nature;mixed style is mainly applied in the recreational vacation area,connecting all independent scenic spots by water.The design of ecological corridor should follow the principle of "integrated,protective and diversified",attach more importance to the construction of mountain corridor system,ecological road and river corridors.Several species were recommended for vegetation recovery and slope greening in the study area.And corresponding suggestions were given for the planning and design of eco-park in mountainous regions.

Establishment of Safety Guarantee System of Mountainous Tourism——A Case Study of High and Higher Mountains

After summarizing researches on domestic and foreign tourism safety,it was found that there were few research results on mountainous tourism safety,especially tourism safety and tourism safety guarantee system of high and higher mountains with high risk.The paper had concluded hidden dangers and sources of safe accidents of mountainous tourism,and studied tourism safety guarantee system of high and higher mountains.Furthermore,it proposed that tourism safety guarantee system was composed of tourism safety policies and regulations,tourism precaution,tourism safety control,tourism safety rescue and tourism insurance;and finally pointed out components of each factor.