Dewatering Scheme Research Articles

Research on Multi-Objective Optimization Model of Foundation Pit Dewatering Based on NSGA-II Algorithm

This study focuses on optimizing the foundation pit dewatering scheme using the foundation pit dewatering theory and the principles of multi-objective optimization. It explores the development of a multi-objective optimization model and efficient solution technology for foundation pit dewatering. This research focuses on the foundation pit dewatering project at the inverted siphon section of Xixiayuan canal head, specifically from pile number XZ0+326 to XZ0+500. It establishes an optimized mathematical model for foundation pit dewatering that incorporates three objectives. Additionally, a dewatering optimization program is developed by utilizing the MATLAB optimization toolbox and the multi-objective optimization algorithm program based on the NSGA-II algorithm (Gamultiobj). The multi-objective optimization mathematical model is solved, and a Pareto-optimal solution set with uniform distribution is obtained. The multi-objective optimization evaluation system based on AHP is constructed from the three aspects of dewatering cost, the impact of settlement on the environment, and the safety and stability of the foundation pit. The optimization scheme of the Pareto-optimal solution set is selected as the decision result to provide multiple feasible schemes for the dewatering construction of foundation pits. The optimization scheme is verified by using the GMS software. The simulation results demonstrate that the optimization scheme fulfills the requirements for water level and settlement control. Moreover, the developed optimization program efficiently solves the multi-objective optimization problem associated with foundation pit dewatering. Lastly, an evaluation system incorporating the NSGA-II algorithm and AHP is developed and utilized in the context of dewatering engineering in order to offer multiple viable optimal dewatering schemes.

Numerical evaluation of a 70-m deep hydropower station foundation pit dewatering

The foundation pit of Yamansu hydropower station has an average depth of 70 m and has been excavated with five-level slopes. Lowering of groundwater level is important in excavation. In this study, drainage and pumping were conducted in dewatering. Pumping tests were performed to reverse hydraulic parameters and calibrate numerical models. Numerical simulations were performed to evaluate the dewatering scheme. In the first stage, powerhouse tailrace canal was excavated and used as a drainage channel to lower the groundwater level. Drawdown and hydraulic gradient were evaluated to prevent potential water inrush, erosion, piping, and slope failure. In the second stage, cutoff wall and pumping wells were evaluated to reduce the groundwater level. The influences of depth, permeability, and thickness of the cutoff wall were evaluated. Dewatering scheme was revised accordingly based on the evaluation. The optimized dewatering scheme, which can be used as a reference in similar engineering projects, was performed and verified successfully.

Optimization schemes for deep foundation pit dewatering under complicated hydrogeological conditions using MODFLOW-USG

The design and optimization of the dewatering scheme for deep foundation pits in a highly permeable heterogeneous layer are critical to protect water resources, control subsidence and mitigate environmental impacts. Numerical simulation is an important and sometimes the only tool in the design of dewatering schemes, especially when the dewatering projects are planned under complex hydrogeological conditions with limited data. The open excavation method was chosen for a project to drain a deep foundation pit (35–44 m) in an upland river valley landscape. Quaternary alluvial deposits (129.0 m thick) are generally distributed in the riverbed and the overburden consists mainly of alluvial-diluvial sandy gravel cobbles, clayey soils, sandy clay, and silty fine sand, making the study area very heterogeneous. There may be water inrush from foundation pit, uneven subsidence and deformation due to the uneven structure of the sand and slope stability. MODFLOW-USG (Unstructured Grid) and Subsidence and Aquifer-System Compaction (SUB) Package were used to create a coupled 3-D groundwater flow-subsidence numerical model for foundation pit dewatering. MODFLOW-USG provides greater flexibility in the design of the grid to achieve a high degree of accuracy in numerical simulation, while effectively reduces computational costs. A combination of waterproof curtain and a partial penetrating well was proposed for lowering the groundwater table. The optimized dewatering scheme with a curtain depth of 60 m and a hydraulic conductivity of 0.00518 m/d, and four rows of dewatering wells with an equal row spacing of 40 m, well depth of 50 m, and well spacing of 12.5 m in each row can meet the dewatering requirements with minimum groundwater discharge in the scenarios. The numerical simulation of this study provides a powerful and useful tool for dewatering and subsidence control of deep foundation pit under complex hydrogeological conditions.

The impacts of high salinity and polymer properties on dewatering and structural characteristics of flocculated high-solids tailings

In seeking to better understand the inline flocculation technique for enhanced water recovery from concentrated fine-particle suspensions, polymers of different molecular weight (MW) and chemistry were used to treat a synthetic tailings slurry in a low-shear mixer for continuous flocculation under controlled conditions. The effects of dissolved salts in the slurry and polymer solution make-up water on dewatering performance were evaluated for conventional acrylamide/acrylate copolymers (BASF Magnafloc® products) and an alternative functional chemistry polymer (BASF Rheomax® DR 1050). The properties of the separated liquid and solid phases were examined to understand the impacts of salinity and polymer type on the formation of rapidly dewatering flocculated material. Higher concentrations of NaCl (0.006–0.6 M) and CaCl2 (0.006–0.06 M) salts in the unflocculated slurries formed larger coagulated structures, with focussed beam reflectance measurement (FBRM) showing greater pre-aggregation for the divalent salt. NaCl slurries show edge-to-edge (EE) and edge-to-face (EF) inter-particle associations that are open and easily disrupted while more compact face-to-face (FF) contacts are observed in CaCl2 slurries. For concentrated NaCl slurries, the dosing of medium-to-high MW polymers is generally preferred to maximise net water recovery, with the implication being that bridging mechanisms are still at play in high solids applications. In calcium-enriched slurries, the lower MW conventional copolymer gave comparatively better water returns than the other polymers when applied under low shear conditions, highlighting quite distinct aggregation processes compared to low solids flocculation. These results provide insight on the fundamental complexity of the ionic strength dependence of high solids-high dosage tailings flocculation, towards informing reagent polymer dosing and offering greater flexibility for end-of-pipe dewatering schemes.

Investigation on Dewatering of a Deep Shaft in Strong Permeable Sandy Pebble Strata on the Bank of the Yellow River

This paper reports the dewatering scheme of a deep excavation in sandy pebble strata. The excavation is in high permeability strata and is close to the Yellow River, making the dewatering difficult during construction. At present, few researchers have specially studied the dewatering scheme of deep excavations in strong permeable strata near the water resource. Field pumping test was conducted before the excavation activity, and the permeability coefficient of the strata was obtained by reverse analysis. According to the characteristics of the project, the dewatering scheme of “ waterproof curtain + base grouting + pumping ” was proposed. The influence of vertical waterproof curtain and base grouting on dewatering was analyzed by numerical simulation. In the construction process, the field water table and ground settlement were measured. The results show that (1) the groundwater table versus permeability coefficient curve shows three different stages and (2) the dewatering scheme of “ waterproof curtain + base grouting + pumping ” is effective for deep excavation in strong permeable strata.

Deformation Responses and Mechanical Mechanism of Existing Tunnel due to New Building Construction

This study mainly investigated the variation law and mechanical mechanism of surrounding earth pressure and deformation of an existing tunnel, caused by dewatering, foundation excavation, building loading, and groundwater recovery. According to different dewatering schemes, two modes were established: nonisolated dewatering unloading‐loading mode and isolated dewatering unloading‐loading mode. Through large‐scale similar materials model test, the variation law of deformation and surrounding earth pressure of adjacent tunnel under complex unloading‐loading conditions was preliminarily revealed. Based on the size of the prototype project, the test results were further verified by the numerical simulation. The mechanical mechanism of tunnel deformation in different construction stages was analyzed after the comparative study. The results show that the tunnel structure deformation, vertical and horizontal displacement, and torsion occur in the process of building construction. In the nonisolated dewatering unloading‐loading mode, the decrease or rise of the groundwater level significantly reduces (maximum 27.85%) or increases (maximum 35.19%) the surrounding earth pressure of the tunnel. The decrease or increase of the horizontal total stress was much greater than that of the vertical total stress, which leads to the deformation of tunnel structure. The vertical displacement of the tunnel is generally settlement, which mainly occurs in the stage of dewatering and building loading, accounting for 83.21%–100.00% and 25.11%–40.34% of the total settlement, respectively. In the stage of foundation pit excavation and groundwater recovery, the tunnel rises. In the horizontal direction, the tunnel moves towards the foundation pit, mainly in the excavation stage, accounting for 82.77%–86.30% of the maximum value. Due to the uneven change of displacement field and stress field of soil outside the foundation pit, the tunnel torsion occurs. In the isolated dewatering unloading‐Loading mode, the change of groundwater has little effect on the tunnel. In the stage of excavation and construction load, the variation law of tunnel surrounding earth pressure and deformation is similar in the two modes.

The temperature of Britain's coalfields

Low-temperature heat recovery, cooling and storage schemes, using abandoned flooded mine workings, are a viable option for low-carbon heating solutions within many abandoned British coalfields. The temperature of mine water is a useful parameter, coupled with depth to water, sustainable yield and recharge potential, to identify suitable locations and calculate the likely performance of heat recovery schemes. This paper aims to provide the first mapping and synthesis of the temperature of Britain's coalfields to support this emerging technology. Using the best available evidence, a median geothermal gradient of 24.1°C km −1 was calculated for the British coalfields. However, geothermal gradients between separate coalfields can vary from 17.3 to 34.3°C km −1 . The North East, Cumbria and Yorkshire coalfields all have mean geothermal gradients generally >30°C km −1 , whereas geothermal gradients of generally <23°C km −1 are measured in the Warwickshire, South Wales, Staffordshire, Douglas and Fife coalfields. Active dewatering schemes are shown to locally increase the apparent measured geothermal gradient by ingress and mixing of deeper water into the pumping shafts. This baseline spatial mapping and synthesis of coalfield temperatures offers significant benefit to those planning, designing and regulating heat recovery and storage in Britain's abandoned coalfields.

Taking advantage of aquifer heterogeneity in designing construction dewatering systems with partially penetrating recharge wells

During construction dewatering, artificial recharge with wells might be required to discharge the pumped groundwater. On the one hand, artificial recharge wells must be placed as close as possible to the construction site to limit the above-ground space for the dewatering infrastructure and the transport costs, while on the other hand, the distance from the dewatering site must be considerably large to reduce the hydraulic impact and minimize overall pumping costs. Commonly, artificial recharge wells are completed with filter screens that penetrate large portions of the aquifer. The present study investigates the efficiency and potential of artificial recharge with partially penetrating wells (PPWs; filter length of 1 m) in heterogeneous aquifers. This was done by conducting scenario modeling of simple dewatering schemes with one abstraction well and one artificial recharge well, as well as with experimental field tests. In these field tests, artificial recharge on a fully penetrating well (FPW), as well as on a PPW screened at a layer of relatively high permeability (300 m/day), is explored. The present study shows that the use of recharge PPWs screened at depth in high-permeability layers of the aquifer minimize the hydraulic impact at the dewatering site. Scenario modeling shows that recharge PPWs can be installed much closer to the dewatering site than FPWs. Assessment of the optimal screen depth of the PPW, as well as the mutual distance between the wells, requires a proper consideration of the vertical variability in the hydraulic conductivity of the aquifer.

Hydraulic evaluation of a dewatering scheme in shallow aquifers in Kuwait

In heavily populated residential areas lacking adequate subsurface drainage, leakage from urban water supplies and wastewater discharge causes groundwater levels in underlying shallow aquifers to rise. This may have serious consequences for the stability of building foundations, roads and natural landforms. This paper evaluates the performance of a dewatering scheme comprising of 15 vertical wells in two residential areas in Kuwait. The hydraulic effectiveness is evaluated from pumping tests and preliminary numerical modelling. The results show that the scheme can keep the water table at the desired levels over a limited area. The maximum predicted nodal drawdowns after one year of pumping at 16 835 m 3 d –1 were 4.2 and 5.24 m in the two areas. Further investigations are proposed with the objective of optimizing pumping rates.

Optimization Analysis of Deformation of Underlying Tunnel in Dewatering and Excavation of Phreatic Aquifer

This paper theoretically analyzed the deformation law of the underlying tunnel caused by dewatering and excavation of deep foundation pit in the phreatic aquifer area, which is based on the Mindlin solution and the double-sided elastic foundation beam theory, and used the finite difference method and the fluid-solid coupling principle to conduct three-dimensional numerical simulation of dewatering and excavation of deep foundation pit with fluid-solid coupling by using FLAC3D5.00. This research shows that the layered and segmented excavation method from the middle to the end by dewatering the skip layer has a better effect on optimizing the deformation of the underlying tunnel through the simulation of three excavation methods and two dewatering schemes crossing each other, which is about 2.5% less than the layer-by-layer dewatering scheme. In addition, the deformation law of the simulated value is the same as the theoretical value, and the simulated value is slightly larger than the theoretical value. Underlying tunnel only just exists vertical deformation at the direct center of the foundation pit, and the maximum deformation is about 3.054 mm under the dewatering well of the jumping layer and W3. With the dewatering of jumping layer and the third excavation mode (W3), underlying tunnel only just exists lateral displacement at the position where is the retaining structure, and the maximum displacement is 1.606 mm.

Continuous Hydrogeological Characterisation in Iron Ore Deposits Using Borehole Magnetic Resonance

In situ dewatering of iron ore deposits is essential for safe and efficient mining operations, as well as reducing requirements for subsequent moisture removal for processing and transportation. Evaluating porosity, residual moisture content, and hydraulic conductivity is key to designing effective dewatering schemes. Modern borehole magnetic resonance has been used in the oil and gas industry for over twenty years to provide continuous evaluation of porosity, bound and free fluid volumes, and permeability. As such, it is uniquely suited to provide subsurface characterisation data for dewatering scheme design. However, applying these methods in iron ore settings introduces complications that are not observed in typical oil and gas environments due to the high concentrations of paramagnetic and ferromagnetic iron-containing compounds making up the ores. This requires explicitly accounting for the impact of these compounds on surface and diffusional relaxation when estimating fluid volumes and permeability from magnetic resonance measurements. Development of robust methods for accommodating these effects would allow for practical application of borehole magnetic resonance measurements in iron ore settings, providing continuous and cost effective hydrogeological characterisation.

Study of the Damage Mechanics and Dewatering Recovery Programs for the Shield Tunnel under the Yangtze River

A case is presented about damages due to leakage and inrushing water that developed in the segmented pre-casted concrete liner of a shield tunnel under the Yangtze River. Various possible causes were considered to explain the damage mechanism. The opening and distribution due to differential settlement caused by the leakage of biogas or water in the shield tunnel were analyzed. The damage mechanism of the aquifuge, which occurred under the tunnel through exertion of a high piezometric head in the lower confined aquifer, was analyzed. The tensile-shear damage mechanism of the aquifuge was studied, and the judgment formulas, which were used to determine whether surface water bursting occurred, were derived. Two dewatering recovery programs were simulated by the finite difference method in conjunction with MODFLOW software. From the simulation results, the hydraulic gradient and settlements caused by decreased pore pressure were calculated. The optimal dewatering scheme and protection measurements are suggested.

Study on the damage mechanics and dewatering recovery programs for shield tunnel

A case is presented about damages due to leakage and inrushing water that developed in the segmented precasted concrete liner of a shield tunnel under the Yangtze River. Various possible causes were considered to explain the damage mechanism. The opening and distribution due to differential settlement caused by the leakage of biogas or water in the shield tunnel were analyzed. The damage mechanism of the aquifuge, which occurred under the tunnel through exertion of a high piezometric head in the lower confined aquifer, was analyzed. The tensile-shear damage mechanism of the aquifuge was studied, and the judgment formulas, which were used to determine whether surface water bursting occurred, were derived. Two dewatering recovery programs were simulated by the finite difference method (FDM) in conjunction with MODFLOW software. From the simulation results, the hydraulic gradient and settlements caused by decreased pore pressure were calculated. The optimal dewatering scheme and protection measurements are suggested.

Efficient flocculation of microalgae for biomass production using cationic starch

In order to make algal biomass a suitable feedstock for fuel and bioproducts, a practical means of dewatering and concentrating the algal cells must be devised. An effective algal dewatering scheme will most likely utilize flocculation as an initial concentrating step. Cationic starch could prove to be an effective flocculant for economical production of uncontaminated microalgal biomass. This investigation seeks to ascertain whether or not cationic starch is an effective flocculant for the freshwater green alga Scenedesmus dimorphus. Evidence from extensive flocculation tests showed cationic starch to be effective at low dosages, approximately 0.08g cationic starch to g algal biomass, for both growth phase and stationary phase S. dimorphus. Algal cell restabilization occurred at lower starch concentrations in the growth phase than in the stationary phase. The tests also indicated that flocculation was effective with degrees of cationic substitution from 0.14 to 0.64 with no significant change in flocculation efficiency over that range.

Comparing and Selecting the Dewatering Schemes of Tibet Linzhi Duobu Hydropower Station Underground Factory Buildings

This article which based on the analysis of the Tibet Linzhi Duobu hydropower stations geological conditions, the review of the permeability coefficient, total water inflow estimation of foundation pit and other foundation researches compares and selects water-lowering schemes when the excavation of underground factory buildings starts. Comparing the impervious curtain and water-lowering scheme with full-well dewatering scheme on applicable conditions, advantages and disadvantages, construction program and cost accounting etc. in detail and the final selection is the "drain openly + the well dewatering program. This article also makes a very detailed discussion on construction management, operation mode, safeguard measures and contingency measures and hopes to have references to the follow-up projects.

Overburden failure and the prevention of water and sand inrush during coal mining under thin bedrock

Coal mining under thin bedrock or thick unconsolidated soil layers brings mining problems related to these special geological conditions. The meaning of the term “thin bedrock” is defined through the thickness statistics of the coal seam and the bedrock layer. The coal-bearing strata having thick, unconsolidated aquifers and thin bedrock located at the Taiping Coal Mine in Shandong province were taken as a geological prototype for subsequent study. The geological, hydro-geological and engineering characteristics of the thin bedrock were analyzed. An engineering geological model was than established. Overburden failure and the development of “Three Zones” were studied by physical model tests. The rupture pattern and rock failure were analyzed for mining conditions under thin bedrock. The height of the caving zone and the freely flowing water fractured zone of different mining thicknesses were separately calculated. The results show that a mining thickness greater than 3.5 m causes the height of the freely flowing water fractured zone to be sufficient to touch the weathered zone and the bottom of the Quaternary system aquifer, to various degrees. This, then, would lead to water and sand inrush into the working face. Measures to prevent water and sand flow inrush disasters by eliminating the power source are put foreword. A field dewatering scheme was designed and observational data were obtained. The dewatering project had an obvious effect and the water level at working face number 8309 dropped to a safe level. The average draw down of the groundwater was observed to be 7.86 m. This showed that the dewatering project played a role in decreasing the hydraulic pressure and ensuring safety mining.

Numerical modelling of groundwater pumping processes

Engineers need versatile tools in order to design successful dewatering schemes to counteract the effects of changing groundwater levels in cities. In the present paper, a finite-element program is used to perform pumping analyses, involving moving phreatic surfaces and possible desaturation of materials. First, a problem of local dewatering from a line of wells is analysed, involving desaturation of the soil. The results from an analytical solution as well as those of the numerical model are compared with field data. It is shown that the numerical results, accounting for soil desaturation, are closer to field measurements. Second, the ability of the finite-element program to model falling and subsequently rising groundwater levels in cities due to variable water abstraction (as in the case of London) is assessed. The techniques show promise and are sufficiently flexible to be applied to other geologies and boundary conditions.

Numerical modelling of groundwater pumping processes

Engineers need versatile tools in order to design successful dewatering schemes to counteract the effects of changing groundwater levels in cities. In the present paper, a finite-element program is used to perform pumping analyses, involving moving phreatic surfaces and possible desaturation of materials. First, a problem of local dewatering from a line of wells is analysed, involving desaturation of the soil. The results from an analytical solution as well as those of the numerical model are compared with field data. It is shown that the numerical results, accounting for soil desaturation, are closer to field measurements. Second, the ability of the finite-element program to model falling and subsequently rising groundwater levels in cities due to variable water abstraction (as in the case of London) is assessed. The techniques show promise and are sufficiently flexible to be applied to other geologies and boundary conditions.

Removal of inorganic constituents of biomass feedstocks by mechanical dewatering and leaching

Inorganic constituents of ash in biomass fuels are responsible for equipment failure and operating difficulties in thermochemical energy conversion facilities. Alkali metals, in the presence of chlorine and sulfur, are the leading contributors to this problem. Banagrass, a herbaceous species being considered for use as a dedicated energy crop, contains high levels of potassium and chlorine. Some inorganic elements are water soluble and the opportunity exists to remove them by mechanical dewatering and leaching as part of the feedstock preparation process. Laboratory-scale equipment, representative of processes employed in the commercial extraction of sugar from cane, was used to prepare banagrass fuel treatments that included two degrees of comminution (coarse and fine) and two dewatering schemes (mechanical dewatering only, and a multi-step process consisting of initial mechanical dewatering followed by a water rinse and second dewatering). The treatment that included fine comminution and multi-step dewatering resulted in a fuel with substantial reductions in ash (45%), K (90%), Cl (98%), S (55%), Na (68%), P (72%) and Mg (68%). The coarse comminution and multi-step dewatering scheme also resulted in reductions, but generally with 10–20% more of the initial constituent mass retained in the fuel. These two treatments produced fuels containing 0.11 and 0.23 kg (Na 2O + K 2O) GJ −1, respectively, with corresponding ash fusion temperature estimates of 1250 and 1075°C. By comparison, bagasse, the fibrous by-product of sugar cane, contains 0.06 kg (Na 2O + K 2O) GJ −1 and has an estimated ash fusion temperature of roughly 1500°C. Banagrass subjected to the most severe treatment, fine comminution with multi-step dewatering, should produce a boiler fuel with characteristics similar to those of bagasse.

STOREBAELT EASTERN RAILWAY TUNNEL: CONSTRUCTION.

Keywords AS STOREBAELTFORBINDELSEN, MT GROUP, MONBERG & THORSEN, DYCKERHOFF & WIDMANN, CAMPENON BERNARD, SOGEA, KIE TUNNELS, RAILWAYS, CONSTRUCTION, BORING, CROSS PASSAGES, HAND, MINING, METHODS, CUT AND COVER, CIVIL ENGINEERING, WORKS, GEOLOGY, WATER, PRESSURE, EARTH, BALANCE, MACHINES, MACHINERY, TBM, TUNNELLING, MODIFICATION, UNDERSEA, SUBMARINE, DEWATERING, CRYOGENICS, FREEZING, JUNCTIONING, GLACIAL, TILL, GROUND, TREATMENT, ONSITE, MANUFACTURING, HIGH, STRENGTH, DURABILITY, CONCRETE, LININGS, EPOXY, COVERED, COATED, REINFORCEMENT, CAGES, PROJECTS, MANAGEMENT, CONTRACTS, BORED, JOINT VENTURES, BEHAVIOUR, ALIGNMENT, SURVEYS, MUCK, DISPOSAL, SEABED, WATER, CON STOREBAELT, EASTERN DENMARK, SCANDINAVIA... Show All