Hangzhou Bay Area Research Articles

Long-term agricultural cultivation decreases microbial nutrient limitation in coastal saline soils

Soil enzyme activities are pivotal for diverse biochemical processes and are sensitive to land use changes. They can indicate soil microbial nutrient limitations. Nonetheless, the mechanism governing the response of soil microbial nutrient limitation to land use alterations in coastal regions remains elusive. We assessed soil nutrients, microbial biomass, and extracellular enzyme activities across various land use types—natural (wasteland and woodland) and agricultural (farmland and orchard)—in the Hangzhou Bay area, China. All four land use types experience co-limitation by carbon (C) and phosphorus (P). However, the extent of microbial resource limitations varies among them. Long-term agricultural practices diminish microbial C and P limitations in farmland and orchard soils compared to natural soils, as evidenced by lower ecoenzymatic C:N ratios and vector lengths, alongside higher microbial carbon use efficiency (CUE). Soil nutrient stoichiometric ratios and CUE are primary factors influencing microbial C and P limitations. Thus, fostering appropriate land use and management practices proves imperative to regulate soil nutrient cycles and foster the sustainable management of coastal areas.

Future land use prediction and optimization strategy of Zhejiang Greater Bay Area coupled with ecological security multi-scenario pattern.

The land use changes driven by human activities press a incredible menace to zonal ecological security. As the most active urban cluster, the uncontrolled expansion of cities in the bay area exerts enormous pressure on the ecosystem. Therefore, from the perspective of ecological conservation, exploring future land use optimization patterns and spatial structure is extremely essential for the long-term thriving of the bay area. On this basis, this research integrated the System Dynamics model (SD) as the quantity forecast model and the PLUS model as the spatial emulation model and established the Land Use/Cover Change (LUCC) Simulation Framework by setting the constraints of Ecological Security Multi-Scenario Patterns (ESMP). By setting four scenarios in future, that is, Business As Usual (BAU), Priority of Ecological Protection (PEP), Balanced Development Scenario (BD), and Priority of Urban development (PUD), this research predicts LUCC in the Zhejiang Greater Bay Area (ZGBA) in 2035 and explored land use optimization patterns. The results indicate that by 2035, under the scenarios of BAU, BD, and PUD, the construction land will observably grow by 38.86%, 19.63%, and 83.90%, respectively, distributed mainly around the Hangzhou Bay Area, Taizhou Bay Area, and Wenzhou Bay Area, primarily achieved by sacrificing ecologically sensitive lands such as forests to achieve regional high economic growth. Under PEP, the growth of construction land retards, and forest experiences net growth (11.27%), with better landscape connectivity and more cohesive patches compared to other scenarios. Combining regional planning and analysis at the city scale, Hangzhou Bay area (Hangzhou, Huzhou, Jiaxing, Shaoxing, Ningbo) can adopt the BD development scenario, while Zhoushan, Taizhou, Wenzhou and Fuyang County of Hangzhou can adopt the PEP development scenario. This research furnishes a novel mechanism for optimizing land use pattern in ecological security perspective and offers scientific guidance for land resource management and spatial planning in ZGBA.

Late Holocene Climate Warming Events and Their Linkage to Hydraulic Engineering on the Coast of Hangzhou Bay, East China

The coastal lowlands in East China are very sensitive to climate change and marine disasters, and much large-scale hydraulic engineering was recorded in the historical documents of the Late Holocene. In this study, AMS 14C and OSL were used to date three sedimentary profiles from the north and south coasts of inner Hangzhou Bay, and grain size and geochemical analyses including organic carbon, macro-elements, and alkaline earth metals were performed, while hydraulic engineering records in historical documents were compiled, in an attempt to reveal the sedimentary records of extreme climatic and hydrological events over the past 3000 years and to probe into the correlation between them and hydraulic engineering. The results show that the intensified chemical weathering during ca. 200 BCE to 900 CE in East China corresponded to the warm and humid climate during the Qin-Han and Sui-Tang dynasties. Salinity intrusion with rising local water levels occurred in the lowland plains along the south coast of Hangzhou Bay from 120 to 895 CE. Low-salinity water intrusion from 32 to 488 CE was also recorded in the stratigraphy of lowland plains along the north coast of Hangzhou Bay. The sedimentary records of the East Tiaoxi River basin show river floods about 2000 years ago. The above sedimentary records indicate that the relative sea level rose in the Hangzhou Bay area during the Qin-Han and Sui-Tang Warm Periods, resulting in frequent salinity intrusion and river floods, which coincided with the historical records of hydraulic engineering such as the construction of seawalls, river levees, and the enclosure of lakes for restoration of river floods during the Han and Tang dynasties. Such coincidence reflects that climate change profoundly affected the hydrological environment of the coastal areas in East China as well as the response of the human societies.

The Characteristics and Impact Factors of Sulfate and Nitrate in Urban PM2.5 over Typical Cities of Hangzhou Bay Area, China

PM2.5 pollution over Hangzhou Bay area, China has received continuous attention. In this study, PM2.5 samples were collected simultaneously in six typical cities in Zhejiang Province from 15 October 2019 to 15 January 2020 (autumn and winter) and from 1 June to 31 August 2020 (summer), and major water-soluble ions were analyzed. Average concentrations of NO3− and SO42− in the six cities were 3.93–15.64 μg/m3 and 4.61–7.58 μg/m3 in autumn and winter, with mass fractions of NO3− and SO42− in PM2.5 up to 19.6–34.2% and 13.6–26.3%, respectively, while in summer, they were 1.23–2.64 μg/m3 and 2.22–4.14 μg/m3, with mass fractions of 7.0–15.0% and 14.7~25.1%. Both NO3− and SO42− were mostly from gas-to-particle transformation of precursors. High relative humidity in the six cities was suggested to significantly promote the formation of NO3− and SO42−, particularly in autumn and winter, while enhanced atmospheric oxidation favored the formation of SO42− in summer. However, the formation of NO3− was inhibited under a high temperature of >15 °C. The concentrations of SO42− and NO3 were mostly correlated with each other among the six cities. Potential source contribution function analysis indicated that both SO42− and NO3− were mostly from local pollution of Hangzhou Bay area in Zhejiang Province and also transported from Shanghai and the southern region of Jiangsu Province. This study contributed to the understanding of regional characteristics of SO42− and NO3− in Hangzhou Bay area and suggested that joint prevention and control efforts should be strengthened to reduce regional PM2.5 pollution.

Determination and projection of flood risk based on multi-criteria decision analysis (MCDA) combining with CA-Markov model in Zhejiang Province, China

The determination and projection of flood risk level is an important problem for disaster management decision-makers, especially for densely populated and economically developed Zhejiang Province, China. This study generated a flood risk map for 2020 adopting 11 parameters and projected flood risk maps for 2025 and 2030 by adopting the CA-Markov method spatially. The data were first homogenized using the fuzzy method. Next, the analytic hierarchy process (AHP) method calculates the weight of each parameter and generates a flood risk distribution map. Statistical analysis of flood disasters in the study area and the support of other research results showed that the proposed model performed well in mapping flood risk. The map showed that 15.19% of the study area was in the high-and extremely high-risk classes, and was mainly concentrated in the southeast coastal area and Hangzhou Bay area. The Receiver Operator Characteristic (ROC) curves (AUC2015 = 0.887, AUC2020 = 0.891) verified the excellent performance of the CA-Markov method in projecting flood risk. Finally, the CA-Markov method was adopted to project the risk distribution map of future flood areas, and the results showed that the high-risk areas for flooding in the southeast coastal area and northern Hangzhou Bay area will be further expanded in 2025 and 2030.

Evaluation of ecosystem services budget based on ecosystem services flow: A case study of Hangzhou Bay area

Ecosystem services (ESs) flow, the spatial transfer of ESs from supply to demand, is critical but remains underexplored. Traditional studies often quantify ESs flow by crudely overlaying supply-demand, which lacks authenticity. This work develops a simulative model based on the flow-medium-path agent to simulate and quantify ESs flow, and subsequently evaluate regional ESs budget by incorporating ESs flow, because ESs aren't static but could flow to remote area, thereby altering the supply-demand relationship. Three prominent ESs, crop production (CP), water yield (WY), and carbon sequestration (CS) in Hangzhou Bay area were selected as cases. The results show: (1) a noticeable mismatch between ESs supply and demand; (2) ESs flow appears diverse features, e.g., the WY flow is single-directional and can only deliver to the downstream, determined by the topography; (3) Traditional ESs budget reveals the number of towns as supply exceeding demand for CP, WY, and CS is 313, 411, and 171. Contrastively, regional final budget considering ESs flow suggests that is 202, 581, and 0 as supply-demand balanced, indicating the ecological state is altered by integrating ESs flow into ESs budget evaluation. This study contributes to the researches on ESs comprehensive evaluation, ESs flow quantification, and ecological strategies references.

The Influence of Geological Conditions in the Hangzhou Bay Area on the Deformation Behavior of Deep Excavations

The deformation behavior of deep excavations is affected by many factors, among which the geological conditions are greatly affected. Hangzhou Bay is affected by marine siltation and river alluvium, and the geological conditions within the urban area of Hangzhou are quite different. In this paper, the geological and deformation data of 79 deep excavation cases in the Hangzhou urban area were collected, and the statistical analysis showed that the deformation control of excavations in the silt area was poor. The average maximum lateral wall displacement of deep excavations of the Hangzhou urban area was 0.41%H (H was the depth of the excavation), the average value of the alluvial area was 0.22%H, and the average value of the silted area was 0.55%H. The influence of geological conditions, wall type, and construction period on the deformation of excavations was compared, and the deformation behavior of excavations in the silted area was clearly affected by various factors.

Ecosystem Carbon Storage in Hangzhou Bay Area Based on InVEST and PLUS Models

The study of the relationship between the land use and carbon storage of ecosystem services is of great significance to regional carbon emission management. It can provide an important scientific basis for the management of regional ecosystem carbon pools and the formulation of policies for emission reduction and foreign exchange increases. The carbon storage component of the InVEST model and the PLUS model were used to study and predict the temporal and spatial variation characteristics of carbon storage in the ecological system and their relationship with land use type for the periods of 2000-2018 and 2018-2030 in the research area. The results were as follows:the carbon storage in 2000, 2010, and 2018 in the research area was 7.250×108, 7.227×108, and 7.241×108 t, respectively, which suggested that it first decreased and then increased. The change in land use pattern was the main cause of changed carbon storage in the ecological system, and the fast expansion of construction land resulted in the decrease of carbon storage. With its correspondence to land use patterns, the carbon storage in the research area demonstrated significant spatial differentiation and was characterized by low storage in the northeast and high storage in the southwest according to the demarcation line of carbon storage. The resulting prediction was that the carbon storage in 2030 will be 7.344×108 t, with an increase of 1.42% compared with that in 2018, owing mainly to increased forest land. Soil type and population were the two driving factors with the highest contribution to construction land, and soil type and DEM had the highest contribution to forest land.

Environmental profile, potential sources, and ecological risk of polycyclic aromatic hydrocarbons in a typical coastal bay and outer bay area.

As a class of persistent organic pollutants, polycyclic aromatic hydrocarbons (PAHs) are widely present and accumulate in multimedia environments. The pollution characteristics, spatiotemporal distribution, potential sources, influencing factors, and ecological risks of 16 PAHs were investigated in the water-sediment system of the Hangzhou Bay and outer bay area (HZB and OBA, respectively). The total concentrations of 16 PAHs (∑PAHs) were 220 ± 97.0 and 130 ± 36.0ng/L in the seawater and 343 ± 179 and 505 ± 415μg/kg (dry weight) in the sediments of the HZB and OBA, respectively. The pollution level of PAHs in the HZB seawater was higher than that in the OBA seawater, but the opposite result was found in the sediments. Moreover, ∑PAHs exhibited high temporal variability in the HZB seawater (rainy season > dry season), whereas ∑PAHs in the sediments showed no significant difference between seasons. The molecular diagnostic ratio method was used to identify pollution sources and showed that the PAHs in seawater came from different pollution sources (fuel combustion and petroleum), whereas the PAHs in the sediments originated from coincident sources (mixed combustion). Correlation analysis revealed that temperature was positively related to ∑PAHs, whereas salinity was negatively related to seawater ∑PAHs values. Ecological risk assessment demonstrated that the potential for adverse ecological effects was low to moderate in seawater but moderate to high in the sediments.

Business credit network characteristics and impact on green economy efficiency: Evidence from the Greater Bay Area around Hangzhou Bay of China.

In regions where the development of formal finance is relatively lagging behind, commercial credit has partially replaced the role of formal finance and facilitated the development of the private economy and even the country, thus making commercial credit an important entry point for understanding and promoting sustainable economic development. Taking the Hangzhou Bay Greater Bay Area as a case study, based on the City Business Credit Environment Index (CEI) from 2015 to 2019, we examine the characteristics of business credit networks using social network analysis and discuss the impact of business credit on urban green economy efficiency heterogeneity by drawing on spatial econometrics. The study confirms that the structure of business credit networks in the Hangzhou Bay Greater Bay Area tends to be dense, the network density and number of connections show growth, the spatial network structure is taking shape, and the strength of spatial connections among cities has increased. Hangzhou, Shaoxing, Jiaxing and Shanghai are at the centre of the network and play a radiation-driven role. The business credit network in the Hangzhou Bay Greater Bay Area is characterised by self-stability and has evolved from a multi-centre to a single centre. Business credit is negatively correlated with the efficiency of the green economy in the Hangzhou Bay Area, which is a departure from the Chinese "financial development paradox". In terms of heterogeneity, the relationship remains consistent for port cities and open coastal cities in general, while the effect is less pronounced for cities above sub-provincial level. The study concludes that, with the high-quality economic development of the Hangzhou Bay Greater Bay Area, the Chinese "financial development paradox" does not exist in the region at this stage, which also highlights the need to accelerate the construction of a Chinese-style modernisation theory and practice system.

Long-Term Spatiotemporal Changes in Ecosystem Services Caused by Coastal Wetland Type Transformation in China’s Hangzhou Bay

Coastal wetlands provide essential ecosystem services, while usually experiencing land transformation or degradation mainly due to intense anthropogenic activities and climate changes. Understanding the changes in wetlands ecosystem services is essential to decision makers for generating sound coastal planning. Hangzhou Bay is rich in wetland resources, and the urbanization of Hangzhou Bay in the past three decades has caused fundamental changes in the wetlands in the region. Based on the remote sensing images of the Hangzhou Bay area from 1990 to 2020, this paper analyzes the land use situation of the Hangzhou Bay area in seven periods. This paper calculates the area transfer matrix of various types of wetlands. It uses the InVEST model to evaluate the changes in the function of wetland ecosystem services in the Hangzhou Bay area. Hangzhou Bay wetlands show a trend of transferring natural wetlands to artificial and non-wetlands from 1990 to 2020. Carbon stocks fell by 14.24%. The annual water production decreased by 33.93% and then returned to the original level. The area of habitat degradation increased by 79.94%. The main influencing factors are paddy field degradation, increase in non-wetland area, and decrease in sea area. This paper proposes that the development and construction of farmland in the “red line” area and established wetland reserves are prohibited, and to strengthen the training of wetland management personnel, establish a sound decision-making consultation mechanism, and increase the scientific research expenditure on wetlands in the region.

Sources and distribution of microplastics in the east China sea under a three-dimensional numerical modelling

Microplastics are new pollutants found in various environments; moreover, high concentrations of microplastics have been proved to harm aquatic organisms. To understand the high abundance of microplastics in the East China Sea (ECS), where the Zhoushan fishing ground is located, this study investigated the transportation and spatial distribution of microplastics from the Changjiang River Estuary (CE) to the ECS via three-dimensional numerical modelling. Utilising observations of microplastics at the surface of the ECS and backward particle tracking, three sources of microplastics were identified: the Changjiang River, Hangzhou Bay, and coastal area of Nantong city. Moreover, Southern Korea contributed to the microplastics in ECS. After microplastics are released from these sources, monsoons, currents, the Changjiang plume, and tides cause significant seasonal differences in the hot spots for microplastics in the ECS; moreover, the generation of ocean fronts may promote microplastic accumulation. In addition, the settling characteristics of microplastics were shown to influence their distributions; for example, large amounts of microplastics accumulated at the bottom of the riverbeds. This study enables a more complete assessment of microplastic transport from estuaries to the open sea and provides a spatial and temporal distribution of microplastics at the surface of the ECS.

Land Use Change and Ecosystem Health Assessment on Shanghai–Hangzhou Bay, Eastern China

Reasonable quantitative assessment on urban ecosystem health is conducive to the sustainable development of the economy and human society. This paper quantitatively evaluated the impact of land use change on ecosystem services and ecosystem health by building a comprehensive evaluation system (vigor–organization–resilience–ecosystem services), and then analyzed the spatial-temporal pattern, evolution characteristics, and driving factors in the Shanghai–Hangzhou Bay area (SHB) over the 2000–2015 period. The results show that: the area of cropland and forest accounted for more than 65% and was mainly converted into built-up land in the past 15 years. The overall ESV showed a trend of first increasing and then decreasing. Forest accounted for the largest proportion of the total ESV, more than 60% in each year. The ecosystem health value of SBH decreased from 2000 to 2015. At the city scale, the ecosystem health was significantly deteriorated. All cities reached the lowest value by 2015. At the districts/counties scale, the number with the relatively well or well level decreased from 32 in 2000 to 20 in 2015 by 24.64% of the total area. Overall, inland regions of SBH had better ecosystem health situation than coastal areas. The rapid urbanization of population and economy were driving factors for the decline of the ecosystem health. The indicator system of integrating the vigor, organization, resilience, and ecosystem service for ecosystem health assessment is a potential method which could provide a quantitative and comprehensive way for evaluating ecological and environmental effects in the future.

Study on Coupling and Coordinated Development of Ecological Environment-Energy Consumption-Regional Economic Growth in Greater Bay Area around Hangzhou Bay

Environment, energy, and economy often constitute an interrelated and contradictory ternary system. In this study, Greater Bay Area around Hangzhou Bay Area is taken as the main research object, and Guangdong-Hong Kong-Macao Greater Bay Area is taken as the reference object. By constructing the index system of 3E system coordination evaluation model, the coordination degree and coordination status of ecological environment, energy consumption, and economic growth subsystems of the two areas are compared and analyzed, and the coupling relationship between 2E and 3E systems of Greater Bay Area around Hangzhou Bay and Guangdong-Hong Kong-Macao Greater Bay Area is further studied. The results show that the eco-environmental coordination degree and energy consumption coordination degree of the cities in Greater Bay Area around Hangzhou Bay are between 0.4248–0.5668 and 0.4528–0.5874, respectively, which are in the state of weak coordination to primary coordination, while the economic growth coordination degree is between 0.5022 and 0.6878, which is in the state of primary coordination to intermediate coordination. The coupling of 2E system in Greater Bay Area around Hangzhou Bay and Guangdong-Hong Kong-Macao Greater Bay Area shows linear growth and nonlinear growth, respectively (R2 = 0.997), presenting a good coupling development overall. The coupling levels of ecological environment-energy consumption, ecological environment-economic growth, and energy consumption-economic growth in Greater Bay Area around Hangzhou Bay increase by 18.94, 86.72, and 98.20% respectively. The coupling of 3E systems between Greater Bay Area around Hangzhou Bay and Guangdong-Hong Kong-Macao Greater Bay Area presents a nonlinear development trend that is increasing year by year (R2 > 0.99), but the coupling level of 3E systems between the two is still low, both of which are in the primary/weak coordination state, while the overall growth rate of 3E system coupling in Greater Bay Area around Hangzhou Bay is higher than that of Guangdong-Hong Kong-Macao Greater Bay Area.

Optimizing the Compensation Standard of Cultivated Land Protection Based on Ecosystem Services in the Hangzhou Bay Area, China

The significant positive externality of cultivated land ecosystem services leads to the low comparative benefit of cultivated land utilization and then causes practical problems such as the abandonment and non-agriculturalization of the cultivated land, which poses a threat to China’s food security. The existing protection system only focuses on the quantity requirement and food production service of cultivated land and ignores the multi-function of cultivated land as an ecosystem, resulting in insufficient incentives and poor effect. Therefore, it is necessary to optimize the protection’s economic compensation standard by adding the cultivated land’s ecosystem service value in order to comprehensively assess cultivated land resources and correct for externalities. Taking the area around Hangzhou Bay, where the contradiction between cultivated land protection and economic development is prominent, as an example, the values of six typical cultivated land ecosystem services in 2016 was constructed and calculated, including food production, carbon sequestration and oxygen production, water conservation, soil conservation, biodiversity maintenance, and cultural leisure. Combined with ecosystem services’ values and the quality index, we finally determined the new county-level compensation standard of cultivated land protection in the Hangzhou Bay area. The results show that the value of cultivated land ecosystem services present obvious regional disparities, meaning that there exist significant differences in the sustainable use capacity of cultivated land and the necessity of establishing grading compensation standards in the region. Finally, we analyze the rationality and innovation of the new compensation standard model as well as its role in the protection of cultivated land and look forward to promoting the sustainable use of cultivated land through these new incentives.

Tracking of Land Reclamation Activities Using Landsat Observations—An Example in Shanghai and Hangzhou Bay

At present, reclamation—changing ocean areas into inland land cover type for human usage—is one of the major methods for expanding land area around the world to alleviate the problem of land shortage. Thus, reclamation activities play an important role in land area extension. In recent years, reclamation projects have been active in eastern China. However, research on how to determine the initiation of reclamation activity remains very limited. Thus, a method of tracking reclamation activities was proposed in this study to analyze the coastline change due to human activities in Shanghai Lingang New City and Hangzhou Bay area. First, the reclamation area was extracted and separated into sea filling and sea enclosing. Next, the “SEDIMENT” signal track method and the “Eight-Neighborhood” morphological method were used to track dissimilar reclamation types. The historical reclamation activities (including start time and end time) over the recent 30 years were also tracked and obtained. Experimental results indicated that the time tracker accuracy of reclamation activity can reach 83.8%. Thus, this study can provide a reference for tracking coastline change.

Settlement mechanism and improvement of thick silty sand layer overlying mud foundation

Many highways have been built on the eastern coast of China in the past decades. Recently, some engineering problems have emerged after long-term operation. Due to the different properties between the underlying soil and bridge pile foundations, the problem of bumping at the bridge head is inevitable. To study the potential causes and provide insight for future improvement, the settlement of typical highways in the Hangzhou Bay area, which had been open to traffic for more than 10 years, was investigated. After an analytical calculation with the verification of the numerical method and field data, it was indicated that long-term deformation was mainly caused by the poor properties of the lower of the two layers that make up the underlying soil. The trend of the variation of the lower layer keeps increasing at a slow rate during the construction period, resulting in sustained and rapid changes during the following years. Different kinds of ground improvement such as lightweight materials and soil–cement columns generated by deep mixing or jet grouting methods are discussed. The improvement of the lower layer will be more effective. With the analytical method, it is convenient and efficient to calculate and analyse the settlement at different periods, which is significant for design.

Spatio-Temporal Land-Use/Land-Cover Change Dynamics in Coastal Plains in Hangzhou Bay Area, China from 2009 to 2020 Using Google Earth Engine

Land-use classification is fundamental for environmental and water resource evaluation in coastal plain areas. However, comprehensive remote sensing image-based land-use analysis is challenged by the lack of massive remote sensing images and the massive computing power of large-scale server systems. In this paper, the spatial-temporal land-use change characteristics of the Hangzhou Bay area coastal plain are investigated on the Google Earth Engine platform. The proposed model uses a random forest algorithm to assist the land-use classification. The dataset is selected from the year 2009 to 2020 and classified with an average classification accuracy of 89% and Kappa coefficient of 88%. The results show that the land use in the selected region is affected by urbanization, the balance of cultivated land occupation and compensation, construction of economic development zone, and other activities. The investigation also shows that in the past 12 years, land use has changed rapidly, and each land-use type maintains the dynamic balance of occupation and compensation. Although the overall land-use distribution is stable, the information entropy fluctuates at a high level, with an average value of 1.15, and the multi-year average value of equilibrium is as high as 0.83. The driving force of land-use change is analyzed and accounted as demographics and human population dynamics, social-economic development, urbanization, and coupling effects of the above-mentioned factors.

Research on the Change of Coastline on the South Coast of Hangzhou Bay Based on Multi-temporal Remote Sensing Images

Coastline is an important geographic background for each coastal area, and dynamic monitoring of coastlines is beneficial to coastal natural protection and further coastal construction and development. Based on the Landsat8 data and Sentinel-2 data from 2014 to 2019, this paper uses a method combining regional growth and edge detection to analyze the Cixi section’s coastline changes on the south bank of Hangzhou Bay. Firstly, the multi-source remote sensing data is preprocessed, and then the MNDWI value of each image is calculated. Then, each image is processed into a binary image by a regional growth algorithm. Eventually, we realize the coastline segmentation by the Canny operator of edge detection. The research represents that the coastline of the south coast of Hangzhou Bay moves toward the ocean year by year, and the length of the coastline generally decreases. The analysis may be caused by human-made activities in Hangzhou Bay Area in recent years, such as river cut-offs and urban construction. The research in this paper provides a reference for the protection of natural coastlines and human-made coastlines.

Accumulative Deformation Characteristics and Microstructure of Saturated Soft Clay under Cross-River Subway Loading.

The cross-river subway in the Hangzhou Bay area often passes through deep, thick, soft soil at the bottom of the river. At the same time, overlying erosion, siltation, and changes in water levels adversely affect the deformation of the subway, thereby causing hidden dangers to its safe operation. Using two-way dynamic triaxial testing, the effects of cyclic loading of the cross-river subway on the soft clay foundation were investigated for the first time, using simulation methodology as the prime objective of the present study. A strain development curve for the soft clay was obtained as a result. Considering the effects of effective confining pressure (p′) and radial cyclic stress ratio (τr), an explicit model of accumulative strain on soft clay under cyclic loading of the cross-river subway was established. The results showed that the accumulative axial strain (εd) was closely related to p′ and τr. Under certain conditions, as p′ and τr increased, the εd produced by the soil tended to decrease. Furthermore, through non-destructive testing based on nuclear magnetic resonance (NMR), pore distribution and pore size changes in soft clay during cyclic loading were analyzed. It was observed that under the action of the cross-river loading, the large internal soft clay pores were transformed into small pores, which manifested as a significant decrease in the number of large pores and an increase in the proportion of small pores. Lastly, the macroscopic dynamic soil characteristics observed during triaxial testing closely correlated with the microscopic pore size of the soil obtained in the NMR test, which indicated that using pore distribution and pore size changes to describe microscopic changes was a valid method.