Urban Subsoil Research Articles

The Urban Underground Space beneath the Karst Basin of Guilin, China, Revealed by Ambient Seismic Noise Tomography

Abstract Detection of hidden faults and sedimentary layers in the urban subsoil is significant for the utilization of the underground space, earthquake hazard mitigation, and so forth. Guilin, located in southwest China, is well known for the development of the most typical karst landform in the world and has become an international tourist city that needs scientific planning and knowledge of the urban underground space. After collecting waveform data recorded continuously over a period of about 1.5 months by a dense array of 114 short-period seismic stations installed in and around Guilin, we adopt ambient seismic noise cross-correlation method to extract Rayleigh-wave phase velocity dispersion curves within the period range from 0.5 to 5 s and to obtain a high-resolution S-wave velocity (VS) model of the shallow crust above 9 km using surface-wave tomography. The vertical VS gradient image indicates that the sediment thickness of the Guilin Karst basin is about 1–3 km. Sedimentary layers are relatively thick between Yanshan Mountain and Haiyang Mountain, and along the Yi river valley, where karst groundwater may be abundant and used as an important option for urban water supply. Both the absolute VS velocity image and the relative VS anomaly image clearly reveal the occurrence, location, and deep extension characteristics of major faults. Longsheng–Yongfu, Nanning–Guilin, Yaoshan–Yanshan, Baishi, and Guanyang–Hengyang may be regional deep faults cutting through the upper crust at least. The evolution of the basin is mainly controlled by the steep dipping Longsheng–Yongfu and Baishi faults, and partially controlled by the gently dipping Nanning–Guilin fault in the interior of the basin. The Nanning–Guilin fault is an active and partially buried fault obliquely crossing Guilin city. Urban seismic imaging, such as the new VS tomography presented here, can play an important role in understanding tectonic and tectonic-subsidence earthquake hazards associated with these buried faults.

Assessing and Analysing the Potential of Urban Subsoil: A Case Study of Rabat, Morocco

Assessing and Analysing the Potential of Urban Subsoil: A Case Study of Rabat, Morocco

Urbanization Affects Soil Microbiome Profile Distribution in the Russian Arctic Region.

Urbanization in the Arctic results in considerable and still poorly known environmental consequences. The effect of urbanization on soil microbiome—an ecosystem component highly sensitive to anthropogenic disturbance—remains overlooked for the Arctic region. The research compared chemical and microbial properties of the natural Podzol soils and urban soils of Murmansk—the largest Arctic city. Particular attention was given to the profile distribution, which is almost completely ignored by most microbial studies. Soil microbiome was investigated by the quantitative indicators based on fluorescence microscopy (microbial biomass) and PCR real-time methods (amount of rRNA genes copies of archaea, bacteria, and fungi). The principal changes in urban soils’ properties compared to the natural references included a shift in pH and an increase in C and nutrients’ contents, especially remarkable for the subsoil. The numbers of rRNA genes copies of archaea, bacteria, and fungi in urban topsoils (106–1010, 109–1010, and 107–109, respectively) were lower than in Podzol; however, the opposite pattern was shown for the subsoil. Similarly, the total microbial biomass in urban topsoils (0.55–0.75 mg g−1) was lower compared to the 1.02 mg g−1 in Podzols, while urban subsoil microbial biomass was 2–2.5 times higher than in the natural conditions. Both for urban and natural soils and throughout the profiles, fungi were dominated by mycelium forms; however, the ratios of mycelium–spores were lower, and the amount of thin mycelium was higher in urban soils than in natural Podzols. Urbanization in the Arctic altered soil morphological and chemical properties and created a new niche for microbial development in urban subsoils; its contribution to biodiversity and nutrient cycling promises to become increasingly important under projected climate change.

Coupling detailed urban energy and water budgets with TEB-Hydro model: Towards an assessment tool for nature based solution performances

Nature-based solutions (NBS) are increasingly promoted to mitigate urbanization effects, such as the urban heat island. The release of latent heat requires the availability of water in the urban soils. Models able to represent both detailed water and energy budgets are needed for a reliable evaluation of NBSs performances. The TEB-Hydro model is a recent hydro-microclimate model that extends the physics of the urban microclimate model TEB-Veg to water processes in urban subsoil in order to represent more realistically coupled water and energy budgets. Hence, the aim of this paper is to evaluate the TEB-Hydro model regarding how the water processes affect the energy balance. The model is applied to an urban French catchment for which both hydrological and microclimate data are continuously collected. The model shows general good performances in both simulating latent and sensible heat fluxes. Nevertheless, soil water contents are slightly underestimated during wet periods and overestimated during dry periods. Compared to the previous version of the model (TEB-Veg) with a simplified water budget, TEB-Hydro tends to more overestimate latent heat fluxes than TEB-Veg during dry periods. During wet periods, however, TEB-Hydro simulates better sensible heat fluxes and latent heat fluxes.

The influence of bottom-up anchors pre-tension optimization on the prediction of pit walls rockfall displacements

Introduction. Currently in Russia, innovations in urban subsoil facilities construction are among the key factors of economic development. To improve the efficiency of holding a pit wall in restraint urban conditions and prevent soil loosening around the pit, it is proposed to optimize the pre-tension forces of the bottom-up anchors. It has been determined that the pre-tension forces of the active anchors create extra retention forces in the sliding wedge and, in some specified sense, reinforce the walled soil. Research methodology. When modeling the complex calculation of a pit wall, 4 main stages of the pit excavation and 3 stages of preliminary level tensions of anchor ties were preset. The numerical solution of the beam bending problem is the basic method of calculating the walling strength; the beam laying on the elastoplastic base and retained by the anchors as bonds. The bottom-up anchor structure is modeled in the operating environment of GeoWall software. The values of bottom-up anchors pre-tension are set following the ordinates of forces in the anchors, obtained from the walling stability calculation by the deterministic approach. Experimental research was carried out of the impact made by pit opening stages on the walling stress strained state. Results. Analysis and discussion. The efficiency of bottom-up anchors optimal pre-tension, according to the research results, is obtained by constructing the diagrams reflecting the correlation dependence between the anchors loading and the walling displacement. An obvious advantage of the software is the opportunity to calculate walling and retaining structures stage by stage ignoring their construction technologies. Experimental calculation in GeoWall has shown a high bearing capacity of the bottom-up anchor support. Summary. The nature of the obtained dependence between the anchor longitudinal forces and the pit walling horizontal displacement reflects the actual situation. Thus, for a quiet expectable value of horizontal displacement, it is required to correct the optimal value of pre-tension using the empiricalformula dependences.

Towards Urban Archaeo-Geophysics in Peru. The Case Study of Plaza de Armas in Cusco.

One of the most complex challenges of heritage sciences is the identification and protection of buried archaeological heritage in urban areas and the need to manage, maintain and inspect underground services. Archaeology and geophysics, used in an integrated way, provide an important contribution to open new perspectives in understanding both the history of cities and in helping the decision makers in planning and governing the urban development and management. The problems of identification and interpretation of geophysical features in urban subsoil make it necessary to develop ad hoc procedures to be implemented and validated in significant case studies. This paper deals with the results of an interdisciplinary project in Cusco (Peru), the capital of Inca Empire, where the georadar method was applied for the first time in the main square. The georadar method was successfully employed based on knowledge of the historical evolution of Cusco and the availability of archaeological records provided by some excavations nearby the study area. Starting from a model for the electromagnetic wave reflection from archaeological structures and pipes, georadar results were interpreted by means of comparative morphological analysis of high amplitude values observed from time slices with reflectors visualized in the radargrams.

Relations Between Urban Subsoil and Climate Change in Different Neighborhoods of Rio de Janeiro

Abstract Most cities have grown in a disorderly manner without planning or concern for the environment while urban infrastructure networks were emerging and being implemented. Furthermore, it is known that impacts on the environment such as increasing the soil-sealing rate favor increases in temperature and the formation of heat islands leading to climate change. Therefore, the study objective was to analyze the impacts of disorderly occupation of the urban subsoil by underground infrastructure networks on permeable areas and their relationship with climate change. The methodology was based on bibliographic research and a field survey. It was found that the greater the disorderly occupation of the urban subsoil, the smaller the areas destined as green and permeable areas and the greater the vulnerability to climate change.

Biosolids Improve Urban Soil Properties and Vegetable Production in Urban Agriculture

Exceptional quality (EQ) biosolids may be used to rehabilitate disturbed urban soils for vegetable production in urban gardens. The objectives of this study were to investigate the effects of various EQ biosolids products on urban soil properties and vegetable yield. Field research was conducted at Blacksburg, VA, in an urban subsoil fill from a nearby construction site. Three EQ biosolids products were applied biannually at agronomic nitrogen (N) rates (fall 2016–2017, and summer 2017–2018) and annually at land reclamation rates (5× agronomic N rate; fall 2016–2017). A heat‐dried and pelletized EQ biosolids product and inorganic fertilizer were applied biannually at agronomic N rate only. Biosolids increased soil C storage vs. the control by 37 to 84% after 2 yr. Soil N availability was less than expected based on previous greenhouse research even after cumulative biosolids rates. Lower N availability likely was due to low organic matter and high clay concentrations that reduced organic N mineralization. Cabbage [Brassica oleraceaL. var.capitataL.] (∼3.1 kg m–2) and Siberian kale [Brassica napusL. subsp.napusvar.pabularia(DC.) Alef.] (∼1.1 kg m–2) yields were greater with reclamation rates than with the inorganic fertilizer (1.0 kg m–2and 0.4 kg m–2, respectively) in fall 2017. Despite limiting soil physicochemical conditions, biosolids addition at reclamation rates showed greater potential to increase vegetable yield after 2 yr of application.

Improvements to the hydrological processes of the Town Energy Balance model (TEB-Veg, SURFEX v7.3) for urban modelling and impact assessment

Abstract. Climate change and demographic pressures are affecting both the urban water balance and microclimate, thus amplifying urban flooding and the urban heat island phenomena. These issues need to be addressed when engaging in urban planning activities. Local authorities and stakeholders have therefore opted for more nature-based adaptation strategies, which are especially suitable in influencing hydrological and energy processes. Assessing the multiple benefits of such strategies on the urban microclimate requires high-performance numerical tools. This paper presents recent developments dedicated to the water budget in the Town Energy Balance for vegetated surfaces (TEB-Veg) model (surface externalisée; SURFEX v7.3), thus providing a more complete representation of the hydrological processes taking place in the urban subsoil. This new hydrological module is called TEB-Hydro. Its inherent features include the introduction of subsoil beneath built surfaces, the horizontal rebalancing of intra-mesh soil moisture, soil water drainage via the sewer network and the limitation of deep drainage. A sensitivity analysis is then performed in order to identify the hydrological parameters required for model calibration. This new TEB-Hydro model is evaluated on two small residential catchments in Nantes (France), over two distinct periods, by comparing simulated sewer discharge with observed findings. In both cases, the model tends to overestimate total sewer discharge and performs better under wet weather conditions, with a Kling–Gupta efficiency (KGE) statistical criterion greater than 0.80 vs. approximately 0.60 under drier conditions. These results are encouraging since the same set of model parameters is identified for both catchments, irrespective of meteorological and local physical conditions. This approach offers opportunities to apply the TEB-Hydro model at the city scale alongside projections of climate and demographic changes.

LANDSLIDE RISK MANAGEMENT IN THE URBAN DEVELOPMENT OF SANDNES (NORWAY)

Abstract. The research reported focuses on the multi-causal landslide risk in Sandnes (Norway) in connection with the climate change, the use of the land and the geological/geotechnical properties of the urban subsoil. The municipality is giving special focus on the potential climate change challenges in the development plans of the city and the weather is a significant triggering factor of landslides. The average annual precipitation is 1290 mm and the Norwegian Environmental Agency (NEA) estimates a 10 % increase by 2100 and a 40 % increase for the short-term rainfall (3 h). In addition, the NEA expects sea level to rise between 59 and 89. The study includes records of land use, demographic growth (+1.5 % annually), historical maps and aerial imagery. Events occurred in the past have been inventoried by interviews and document retrieval. Additionally, geological, geotechnical and hydrogeological data from surveys performed in the area have been gathered. The data material is georeferenced in a GIS database for visualization and further treatment. We give special attention to the quality and density of the data to account for the uncertainty and lack of information for certain subareas within the geographical boundaries. This will provide guidance for future work such as soil sampling campaigns. A multi-layered model has been created combining the different aspects studied: elevation, slope, hydrology, historical information and geological data. We model the urban area theoretically affected by the sea level rise and the potential effects on different soils. Finally, the work includes preliminary landslide hazard and vulnerability maps of the present urban plot.

Geotechnical map of a coastal and industrialized urban area (Avilés, NW Spain)

ABSTRACTGeotechnical mapping of urban environments is usually constrained by the scarcity of outcrops during fieldwork. Such is the case of Avilés, a coastal Spanish city that has been heavily industrialized since the middle of the last century. This research approaches the study of its urban subsoil through the development of a Geographical Information Systems-based relational database containing thousands of unpublished ground data, partially extracted from geotechnical reports. This allowed analysing the distribution and changes of thickness of the superficial deposits and lithostratigraphic formations as well as the evaluation of their main geotechnical properties. Thus, 14 geotechnical units were differentiated (hierarchically displayed in three categories) depending on lithological, geotechnical and constructive criteria. As a result, this investigation provides a geo-engineering map at scale 1:25,000.

Urban underground development confronted by the challenges of groundwater resources: Guidelines dedicated to the construction of underground structures in urban aquifers

Urban subsoil provides space, groundwater, geothermal energy and geomaterials, and the importance underlying the management of this strategic space is well-known. In the context of vertical urban growth, groundwater management is a crucial issue. In particular, operational tools dedicated to urban planners are needed in urban areas prone to conflicts over use in order to aid the decision-making process. The aim of this paper is to propose guidelines dedicated to urban underground development in view to incorporating groundwater resource management. These guidelines are supported by analyses of the scientific literature dealing with: (1) the impacts caused by underground structures on urban groundwater, and (2) the quantitative overview of urban groundwater resources at the operational level in terms of quantity, quality and temperature. Finally, perspectives are discussed regarding the research work needed to ensure better management of urban groundwater resources confronted by underground development.

A typology of anthropogenic deposits as a tool for modeling urban subsoil geochemistry: example of the Ile de Nantes (France)

Purpose Urban soils may be contaminated not only by industrial activities but also by the materials contained in the anthropogenic deposits. In order to anticipate the management of excavated soils linked to urban redevelopment, their quality and quantities need to be assessed. Urban soils and subsoils contain nevertheless a large variety of anthropogenic deposits and present important geochemical heterogeneities. The paper aims to develop various geochemical types of made grounds relevant for a 3D urban subsurface model.

Mapping the urban subsoil using ground penetrating radar – challenges and potentials for archaeological prospection

Introduction Over the course of centuries city centres have been continuously changing, developing and adapting to the requirements of society, architectural planning and advancing technology. Urbanisation increases the pressure on cities and towns, causing their expansion and demanding the exploitation of the limited space in their centres. This exploitation is endangering cultural heritage in the urban subsoil, posing a challenge for archaeological prospection to contribute to the preservat...