Dynamic Water Flow Research Articles

Multi-Step Combined Control Technology for Karst and Fissure Water Inrush Disaster During Shield Tunneling in Spring Areas

Shield tunneling in highly fractured karst water-rich conditions easily results in water inrush disaster or even causes the roof of the karst caves to collapse. Severe water inrush disasters have occurred during the EPB (earth pressure balance) shield machine of the Jinan Metro Line R1 advanced through a karst and fissure groundwater-rich limestone ground in the spring area. To cope with the extreme water inrush risk, a multi-step combined control technology was put forward. First, a detailed geological exploration was carried out by ahead geophysical prospecting using high-density resistivity method, geological radar, etc., and geological borehole drilling was conducted from the ground surface before excavation. As a result, the distribution orientation, size, fissure development degree, and water inflow channel within the surrounding rock of the karst caves were detected. Second, multi-step grouting was performed to reinforce the surrounding rock, including pre-grouting treatment and filling rock blocks to the big karst caves from the ground surface, multiple grouting with a small amount of inert slurry each time inside the tunnel, and secondary circumferential hoop grouting at the shield tail. Third, the tunneling process was optimized, including optimizing the tunneling parameters, making full use of the air-pressurized tunneling technology of the EPB to press bentonite into the fractures around the excavation cabin to seal the fissure water, and using the drainage system of EPB and muck improvement technology to reduce the water inrush disaster. Meanwhile, shield protection slurry technology is applied to cutter inspection and replacement in the pressurized chamber under dynamic water flow environment of the spring terrain. The practice shows that the water inrush on the tunnel face is obviously alleviated after the shield machine advanced into the grouting area. According to statistics, the water inflow on the tunnel face decreases from about 4 m3/h before treatment to less than 0.3 m3/h after the abovementioned control, and the water seepage between the segmental linings reduces to almost zero. The average advance rate increased from 3 m/day without stopping or even zero when the shield machine needs to shut down 2–3 days for drainage to about 6 m/day. In addition, the treatments prevented the shield machine from jamming and the head descending disaster. This study provided a reliable control method for shield tunneling through the karst and fissure water-rich area and played an essential role in protecting the spring water.

Progressive Failure Analysis of Slope Water Damage Based on Improved Green-Ampt Infiltration Model

In order to get the law of rainwater infiltration and the law of progressive water damage, the slope of Tianshang bridge foundation in Yunnan Province of China is taken as the engineering basis. The site investigation of the damaged slope is carried out. The traditional Green-Ampt model is improved by considering the ponding effect of dynamic water flow on the slope surface. Based on the variation characteristics of wetting front obtained by the improved infiltration model, the progressive failure process of slope with continuous infiltration is simulated by FLAC3D software. The results show that the water damage of Tianshang bridge slope is mainly caused by the slope absorbing a lot of rainwater in a short time, which has obvious time discontinuity characteristics in time, and shows obvious multi-layer progressive failure characteristics in failure space. The wetting front characteristics obtained by the improved Green-Ampt infiltration model are more consistent with the engineering practice. The water accumulation effect of surface water gradually weakens with the increase of the wet front depth. The slope failure develops gradually from the toe to the top and from shallow to deep. The intermittent failure characteristics provide surplus time for the engineering treatment, the gravel soil slope should be treated after a small-scale water damage occurs.

Life Cycle Assessment of Dynamic Water Flow Glazing Envelopes: A Case Study with Real Test Facilities

High initial costs hinder innovative technologies for building envelopes. Life Cycle Assessment (LCA) should consider energy savings to show relevant economic benefits and potential to reduce energy consumption and CO2 emissions. Life Cycle Cost (LCC) and Life Cycle Energy (LCE) should focus on investment, operation, maintenance, dismantling, disposal, and/or recycling for the building. This study compares the LCC and LCE analysis of Water Flow Glazing (WFG) envelopes with traditional double and triple glazing facades. The assessment considers initial, operational, and disposal costs and energy consumption as well as different energy systems for heating and cooling. Real prototypes have been built in two different locations to record real-world data of yearly operational energy. WFG systems consistently showed a higher initial investment than traditional glazing. The final Life Cycle Cost analysis demonstrates that WFG systems are better over the operation phase only when it is compared with a traditional double-glazing. However, a Life Cycle Energy assessment over 50 years concluded that energy savings between 36% and 66% and CO2 emissions reduction between 30% and 70% could be achieved.

On the effects of pore water pressure buildup and dissipation on the seismic performance of a propped r.c. diaphragm wall in sand

The study concerns the analysis of a retaining structure composed by a couple of r.c. diaphragm walls propped at the crest in loose and medium-dense, variably saturated sand under seismic conditions. Fully coupled dynamic equilibrium conditions and pore water flow in the porous soil have been taken into account, in order to assess the effects that the development and subsequent dissipation of excess pore water pressures can have on the performance of such structures under seismic conditions. To this end, a series of simulations in which the saturated soil permeability is varied of about two orders of magnitude has been carried out, in order to consider different evolution rates for the dynamic consolidation process. The von Wolffersdorff hypoplastic model and the van Genuchten water retention equation have been used to describe the mechanical and hydraulic behavior of the sand. The results obtained in a large series of finite element simulations show a significant dependence of the seismic performance of the structure evaluated in terms of permanent rotations and structural loads, in view of the modern performance-based design criteria on the excess pore pressures buildup during the seismic shaking and on its dissipation with time. For the particular seismic input considered, neither fully drained nor fully undrained conditions can be considered applicable in most of the cases considered. In such conditions, the quantitative assessment of wall and soil displacements, pore water pressures and effective stress distributions within the soil requires necessarily the solution of a fully coupled, nonlinear dynamic consolidation problem.

Fully-coupled analysis for the behaviour of flexible retaining structures under seismic conditions

The study concerns the analysis of the behaviour of two propped reinforced-concrete diaphragm walls in coarse sand under seismic conditions. Fully-coupled dynamic equilibrium and pore water flow under unsaturated conditions for the soil have been taken into account, in order to assess the effects that the development of excess pore water pressures can have on the performance of such structures when dynamic conditions occur. The von Wolffersdorff hypoplastic model and the van Genuchten soil-water retention model have been used to describe the mechanical and retention behaviour of the sand. The Finite Element predictions of the soil and retaining structure behaviour show a significant dependence of the seismic performance of the structure – evaluated in terms of permanent displacements and structural loads, in view of the modern performance-based design criteria – on the excess pore pressures developed in the soil during the seismic shaking, even when dynamic liquefaction does not occur.

Performance improvement of alternate temperature systems with ice storage-based internal water loop

Alternate temperature systems can be found in many areas, e.g., environmental simulation chambers. Circulated air forced convection and refrigerant bypass adjustment are the common ways to control the temperature of the system (or chamber) to be considered. In this paper, we study modified designs with ice storage-based internal water loop. The internal circulated water is cooled by ice melting and the ice is produced by recovering the refrigerant bypass loss. Two methods to change the performance are used: water cooling of the chamber in constant high temperature stage, and refrigerant subcooling in falling temperature stage. The results show that if there is only the water cooling of the chamber, the compressor ON-time will be shortened. The energy consumption can drop in most cases, but the size of the refrigeration device will increase. If both the water cooling of the chamber and the refrigerant subcooling are adopted, the energy consumption and the size of the refrigeration device can be reduced simultaneously. Dynamic water flow rate is documented, which confirms the feasibility of the accurate temperature control of the chamber. As an indicator of the size of the circulated water pump, the maximum water flow rate is also discussed.

Short-Term Optimal Operation of Cascade Reservoirs Considering Dynamic Water Flow Hysteresis

In making short-term optimal operation schemes of cascade reservoirs, water flow hysteresis between the upper reservoir and the lower reservoir is often considered as constant, which cannot really reflect the hysteresis variation between different water flows and will lead to losses of the optimal operation scheme’s benefit. To depict the water flow hysteresis, a Dynamic Water Flow Hysteresis Method (DWFHM) is proposed, based on the space mapping principle. With the mapping operator in the DWFHM, the lower reservoir inflow can be directly obtained. Besides, the DWFHM is used to deal with the hydraulic relation constraint in the short-term optimal operation model of cascade reservoirs. Then, the improved model is applied to the Jinguan cascade reservoirs in the Yalong River basin and solved by an Improved Progressive Optimal Algorithm (IPOA). The results are as follows. (1) Compared with the traditional Fixed Water Flow Hysteresis Method (FWFHM), the inflow processes of the lower reservoir obtained by the DWFHM are more in line with the actual values, due to full consideration of the attenuation effect. (2) The optimal operation with the DWFHM can effectively increase the generated energy (2827 MW·h and 504 MW·h in the non-flood season and the flood season, respectively). Through the analysis of this case, the DWFHM developed in this study can effectively improve the practicability of the optimal operation scheme and reduce the risk in the operation of cascade reservoirs.

Infiltration behavior of heavy metals in runoff through soil amended with biochar as bulking agent

Biochar as a porous carbon material could be used for improving soil physical and chemical properties, while insufficient attention has been paid to potential risks induced by infiltration of heavy metals in the runoff water flowing through biochar-amended soil. Four different soil-biochar matrices with same volumes were constructed including soil alone (M1), biochar alone (M2), soil-biochar layering (M3) and soil-biochar mixing (M4). Leaching experiments were conducted with Pb, Cu, and Zn contaminated runoff water. Results showed that biochar amendment greatly improved the water permeation, and the infiltration rates in M2, M3, and M4 were 2.85–23.0 mm min−1, being much higher than those in M1 (1.33–4.05 mm min−1), though the rates decreased as the leaching volumes increased. However, biochar induced more Pb, Cu, and Zn infiltrated through soil-biochar matrix. After 350-L leaching, M1 retained about 95% Pb, 90% Cu, and 36% Zn, while M2 only retained 4.80% Pb, 17.4% Cu, and 4.01% Zn; about 30% Pb, 80% Cu, and 15% Zn were retained in M3 and M4. Notably, Zn was trapped first and then re-leached into the filtrate, which resulted in a much higher effluent Zn than the influent Zn at the later stage. However, the unit weight of biochar showed a higher capacity for retaining heavy metals compared to per unit of soil. Under the dynamic water flow, all benefits and disadvantages induced by biochar were weakened with its physical disintegration. Biochar as soil amendment can enhance plant growth via ameliorating soil structure, while it would pose risks to environment because of large penetration of heavy metals. If biochar was compacted to form a denser physical structure, perhaps more heavy metals could be retained.

Development and verification of a soil–water coupled finite deformation analysis based on u–w–p formulation with fluid convective nonlinearity

Most soil–water coupled analyses of saturated soil are based on the u–p formulation, where a set of equations is reduced by assuming that the acceleration of the fluid phase relative to that of the solid phase is less than that of the solid phase. Therefore, this analysis cannot be used for a coupled analysis with dynamic water flow in highly permeable soil. This study aims to present a soil–water coupled finite deformation analysis method based on full formulation, or u–w–p formulation. This method differs from conventional methods in the following ways: (1) the governing equations explicitly include the equation of motion for the fluid phase, (2) a relative convective term is used to describe a change in the relative configuration between the two phases, and (3) the moving/inclined discharge boundary is directly implemented to the discretized governing equations. Herein, one/two dimensional seepage and plane-strain deformation analysis results are reported. In the seepage analysis, accelerating permeation of pore water is obtained and the undrained constraint condition is verified. In the deformation analysis, dynamic migration in a high permeable soil specimen, i.e., wave propagation and rotational flow of pore water, is observed.

Koagulacja zanieczyszczeń występujących w wodach powierzchniowych w okresie dynamicznego przepływu

Koagulacja zanieczyszczeń występujących w wodach powierzchniowych w okresie dynamicznego przepływu

Public preferences toward shopping mall interior landscape design in Kuala Lumpur, Malaysia

The number of malls in Malaysia has not only increased dramatically, but they have also been subject to continual expansion over the past few years. Despite this rate of expansion, there has not been enough attention paid to the quality of the spaces and interior landscaping of the malls on the basis of people’s preferences. This study aimed to bring out people’s preferences towards interior public spaces at shopping malls. Using a photo questionnaire, the results pointed to three major dimensions: the green dimension, the seating dimension, and the business dimension in open spaces of shopping malls where the green dimension received the highest preference. The green dimension includes water features, trees, plants, and shrubs. Moreover, legibility and coherence affected people’s preferences for open spaces in shopping malls. People did not prefer the business dimension to spending leisure times, involving business equipment in shopping malls. The study suggested that shopping malls should be designed as truly public spaces with ample public areas. Green elements and water features should be used more in shopping mall public places. Moreover, policy makers can expand the “shopping town” approach for people’s leisure in malls that should include characteristics such as rivers or waterfalls with a dynamic water flow, famous places, public libraries, gardens, town activities, and cultural activities.

Biofilm growth on cohesive sediment deposits: laboratory experiment and model validation

Biofilm growth on cohesive sediment deposits plays a crucial role in the inherent properties of aqueous environment, such as the biostabilization of sediment deposits, sediment-associated contaminant transport, and habitat change. Here, a specially designed cylinder was used for biofilm cultivation under static water (with sediment sizes of 0.02–0.05, 0.05–0.1, and 0.1–0.2 mm) and dynamic water flow conditions. A biomass dynamics model, including the accrual term and detachment term (velocity-dependent and/or autogenic), was proposed to study the effects of sediment size and hydrodynamic condition on biofilm growth. The results showed that more biofilm formed on fine sediment than coarse sediment due to the greater surface area for bacterial attachment and nutrients accumulation. Increased flow velocity inhibited biofilm accumulation and a greater velocity caused more velocity-dependent chronic detachment, resulting in less biofilm growth on sediment particles. Under static water condition, there was more biomass compared with dynamic water flow condition. The proposed model can reasonably reflect the evolution of biofilm growth, as well as the effects of sediment size and hydrodynamic condition, which might be applied for the management of natural aqueous systems.

Analysis of biofilm bacterial communities under different shear stresses using size-fractionated sediment

Microorganisms are ubiquitous in aqueous environments and are crucial for biogeochemical processes, but their community structures and functions remain poorly understood. In this paper, a rotating reactor was designed to study the effects of substrata and flow conditions on sediment bacterial communities using 16S rRNA gene sequencing, assaying three groups of size-fractionated sediments and three different levels of applied shear stress. Proteobacteria, Firmicutes, and Bacteroidetes were the dominant phyla of the microbial communities, with more anaerobic bacteria and opportunistic pathogens being detected under static water conditions, while more aerobic bacteria were detected under dynamic water flow conditions. Most of the top 10 genera were present in all the samples; however, there were significant differences in the species abundance. Paludibacter and Comamonadaceae_unclassified were the most abundant genera under static and dynamic conditions, respectively. Under static water conditions, the medium-grained sediment had the highest microbial diversity, followed by the fine and coarse sediments. Under dynamic water flow conditions, a higher flow velocity corresponded to a greater microbial diversity. Overall, there was no significant difference in the community richness or diversity between the static and dynamic water flow conditions. This study is beneficial for further understanding the heterogeneities of microbial communities in natural aquatic ecosystems.

Concurrent Salinization and Development ofAnoxic Conditions in a Confined Aquifer, Southern Israel.

An ancient, brackish, anoxic, and relatively hot water body exists within the Yarqon-Tanninim Aquifer in southern Israel. A hydrogeological-geochemical conceptual model is presented, whereby the low water quality is the outcome of three conditions that are met simultaneously: (1) Presence of an organic-rich unit with low permeability that overlies and confines the aquifer; the confining unit contains perched horizons with relatively saline water. (2) Local phreatic/roofed conditions within the aquifer that enable seepage of the organic-rich brackish water from above. The oxidation of the dissolved organic matter in the seeping water consumes the dissolved oxygen and continues through bacterial sulfate reduction, with H2 S as a product. These exothermic reactions result in some heating. (3) The seeping water comprises a relatively large portion of the water volume. In the presented case study, the latter condition first developed in the Late Pleistocene following climate change, which led to a dramatic decline in recharge. Consequently, water flow in the local basin has nearly ceased, as evident by old water ages, specific isotopic composition, and nearly equipotential water levels. The continuous seepage from above into the almost stagnant water body has resulted in degraded water quality. Seepages of organic-rich brackish water exist at other sites throughout the aquifer but have limited impact on the salinity and redox conditions due to the dynamic water flow, which flushes the seeping water, that is, the third condition is not met. The coexistence of the above three conditions may explain the development of anoxic and saline groundwater in other aquifers worldwide.

Modeling dynamic non-equilibrium water flow observations under various boundary conditions

Summary Experimental evidence of variably-saturated flow in soils often shows a non-equilibrium between water content and water potential. Such phenomena, summarized by the term “dynamic effects” often occur in laboratory experiments specifically designed for the identification of soil hydraulic properties which are a mandatory input for water flow simulations at the field scale using the Richards equation. Depending on boundary conditions, dynamic non-equilibrium leads either to a relaxation of pressure head for constant water content or vice versa. Diamantopoulos et al. (2012) presented a model which describes dynamic effects in the case of multistep outflow experiments by assuming that the total water content is portioned into two fractions: one fraction which is in instantaneous equilibrium with the pressure head, and a second fraction for which the equilibration of the water content with the pressure is described by a first-order kinetics which leads to a temporal shift in water content at constant pressure head. In this work we applied this non-equilibrium model to four different observations of dynamic non-equilibrium effects presented in the literature and demonstrate that it successfully describes (1) non-equilibrium in water absorption experiments which results in a non-uniqueness of the diffusivity vs water content function, (2) the flow-rate dependence of soil hydraulic properties, (3) dynamic effects in multistep outflow and (4) dynamic effects in multistep flux experiments. We conclude the article by a discussion of possible macroscopic explanations, the consideration of dynamic effects for modeling water flow at the field scale, the uniqueness of the estimated non-equilibrium parameters among different experiments, and further theoretical considerations concerning dynamic effects.

파랑-지반 상호작용에 의한 해저지반의 동적응답 수치해석법 검증

Abstract Seabed may undergo large excess pore water pressure in the case of long duration of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. Thus, it is necessary to develop a numerical technique which can precisely evaluate the dynamic response of seabed due to wave action. In this study, a new numerical technique named mixed model (2D NIT & FLIP models) was proposed. The dynamic wave pressure and water flow velocity acting on the boundary between seabed and the wave field was estimated using 2D-NIT model. This result was used as input data in FLIP program for investigation of dynamic response of seabed. To secure the reliability of the mixed model, the numerical analysis results of the mixed model were compared with Yamamoto’s solution and Chang’s experiment results. The comparison results indicated that there were some differences between them, but the general trend of the effective stress increment and the excess pore water pressure along the depth of seabed was similar to each other. Thus, this study clearly supports the plausibility of the numerical analysis of the mixed model.

Applying image recording and identification for measuring water stages to prevent flood hazards

Information on river stages can be transmitted to relevant management offices over a network by using an automatic stage gauge so that management offices can effectively evaluate whether a river stage is exceeding the warning line and take action if necessary. However, current river stage measurement methods can present this information only in data form because the methods cannot simultaneously obtain images such as the rising or overflow of the river stage. In addition, the stage gauge can fail or be washed away when the river stage is high. To solve these problems, this research evaluates a novel measurement method involving a video surveillance system that exhibits features such as easy installation, low maintenance cost, and low failure possibility. Through on-site image recording, this measurement method involves using image identification technology to read water level figures automatically. This method offers instant river stage figures and on-site video so that disaster prevention measures can be implemented accordingly. The results of a dynamic water flow test conducted in an indoor experimental channel indicated that all of the average absolute error levels of river stage identification were less than ±1.2 %, meaning that the image identification technology could achieve identification results at any flow level. By contrast, the findings of a rainfall simulation experiment suggest that the average absolute error of river stage identification was less than ±2.5 %, meaning that the measurement technology and method used in this research are useful and feasible at various rainfall intensities.

Optimal allocation of water quantity and waste load in the Northwest Pearl River Delta, China

The Northwest Pearl River Delta is one of the most developed areas in China and has faced serious water problems because of its fast economic growth, urbanisation and other developments. It is widely believed that an integrated management of the socio-economic factors cross individual administrative cities is an effective way to solve the water problems. To serve this purpose, this paper aims to develop an integrated model for the optimal allocation of water quantity and waste load. In order to consider the interaction between water quantity and waste load allocation, the Saint-Venant equations were used to simulate dynamic water flow for the water quantity allocation, whereas the one dimensional advection–dispersion mass transport equation was used to simulate water quality for the waste load allocation. In addition to the maximisation of the economic benefits, which is often considered as an objective of optimal water resource allocation models, the minimisation of water shortages and maximisation of waste load were also introduced as objectives of the model. To solve the multi-objective allocation model, a second generation non-dominated sorting genetic algorithm was employed because of its computational efficiency and running time. The results indicate that it is a serious task to reduce the COD in the Northwest Pearl River Delta since the maximum waste load allocations under water quality targets is less than the present amount of waste discharged into rivers in the study area.

Simulation and prediction of phenolic compounds fate in Songhua River, China

The demand for numerical models to simulate and predict the transport and fate of organic pollutants in the environment is a reflection of certain restrictions of experimental research. Various phenolic pollutants have been detected at different concentration levels in the Songhua River, China. A multimedia fate model is coupled with the kinematic wave transport equations to accurately and simply characterize dynamic water flow, velocity and depth. The resulting model is applied to describe the temporal and spatial behavior of eight phenol compounds in the Songhua River. The predictive power of this model is evaluated by statistical tests using field observations during different hydrological seasons of the year 2007. The goodness-of-fit of model prediction for phenolic contaminants is, in general, agreeable. For one focal compound, the pathways and mass fluxes from the river system to the surrounding environment are also evaluated. Uncertainty analysis is performed by Monte Carlo stimulation to judge the influence of variability of input parameters on modeled results. The results indicate that the model has the ability to provide decision makers with valuable reference data for consideration of water pollution controls. Model simulation indicates that phenolic pollution in the river during the low-flow period of 2009 is remarkably reduced when compared to the same period of 2007.

A multimedia fate model to evaluate the fate of PAHs in Songhua River, China

A multimedia fate model coupling dynamic water flow with a level IV fugacity model has been developed and applied to simulate the temporal and spatial fate of Polycyclic Aromatic Hydrocarbons (PAHs) in the Songhua River, China. The model has two components: in the first, the one-dimensional network kinematic wave equation is used to calculate varying water flow and depth. In the second, Fugacity IV equations are implemented to predict contaminant distributions in four environmental media. The estimated concentrations of eight PAHs in Songhua River are obtained, and all simulated results are in acceptable agreement with monitoring data, as verified with the Theil’s inequality coefficient test. The sensitivity of PAH concentration in each environmental phase to input parameters are also evaluated. Our results show the model predicts reasonably accurate contaminant concentrations in natural rivers, and that it can be used to supply necessary information for control and management of water pollution.