Consolidation Of Slurry Research Articles

Effects of a new synthetic Fe-PAM flocculants on filtration and consolidation of bentonite slurry

To improve the dewatering performances of the waste slurry, a new Fe-Polyacrylamide (Fe-PAM) flocculant was synthesized. Comparative analysis with various ionic forms of polyacrylamide (PAM) reveals that the Fe-PAM flocculant has the shortest flocculation time, the lowest optimal shear gradient for flocculation, and the best filtration performance. The capillary suction time (CST) of Fe-PAM treated slurry was improved from 262.3 s (raw sample) to 6.0 s. Moreover, sludge treated with Fe-PAM exhibits the lowest porosity under the same consolidation pressure and the highest permeability at the same void ratio. In addition, mercury intrusion porosimetry (MIP) results indicated that the Fe-PAM-treated sample features the highest number of largesized inter-aggregate pores (average value of 184.2 nm and median value of 23.2 nm) and the greatest pore connectivity (60.55 %), contributing to its superior permeability. The effectiveness of Fe-PAM is further elaborated through a synergistic flocculation mechanism, encompassing the electrical neutralization effect of the inorganic metal Fe3+ and the adsorption bridging effect of PAM's long-chains. This study demonstrates the potential of the synthesized Fe-PAM flocculant to enhance the dewatering efficiency of high-water content slurry and offers valuable insights for synthesizing advanced flocculants in slurry treatment engineering.

Study of design parameters for staged-filled slurry treated by prefabricated horizontal drains under vacuum preloading

The method of using Prefabricated Horizontal Drains (PHDs) placed in layers under vacuum preloading can significantly speed up consolidation of staged-filled soil slurry. The PHDs can settle with the soil slurry and maintain their shape/pattern and dewatering capacity largely in comparison with Prefabricated Vertical Drains (PVDs). This study presents a field trial focused on treating dredged sediments using PHDs under vacuum preloading for land reclamation purposes. The staged filling involved in the field trial is analyzed using a finite strain consolidation model based on the piecewise-linear finite-difference method. Then, the effects of horizontal and vertical spacings of PHDs on settlement and vacuum consolidation rate are evaluated, considering various combinations of variables for staged-filled soil. It is found that for soils with low compressibility, the consolidation rate is primarily affected by the vertical spacing of PHD layers. For soils with higher compressibility, the consolidation rate is more significantly affected by the horizontal spacing of PHDs, and the final settlement after vacuum preloading is mainly influenced by the vertical spacing of PHD layers. This study provides practical recommendations for cost-effective design of horizontal and vertical spacings of PHDs in efficiently treating soil slurry with different compressibility and initial conditions.

Application and Prospect of Curtain Grouting Technology in Mine Water Safety Management in China: A Review

In China, mine curtain grouting has become an important technology to ensure the safe and efficient mining of deep mineral resources and protect regional groundwater resources after more than 60 years of development and improvement. This review paper summarizes and analyzes four aspects of the current situation of curtain grouting technology in deep underground mines: curtain construction conditions, theoretical design and effects, drilling structures, and grouting materials’ research and development. In addition, several main problems of curtain grouting technology in deep underground mines are analyzed: planning and construction lag behind; the theory of mine curtain grouting is not mature enough; the investigation into the mechanism of consolidation and deterioration of grout slurry under long-term high pressure is insufficient; there is a lack of research on the long-term effectiveness of monitoring and evaluation, so precise drilling control technology needs further breakthroughs. In addition, the development directions of this technology are put forward from three aspects: precise directional drilling technology; the consolidation mechanism and durability of slurry under multi-field coupling conditions; and long-term dynamic monitoring, evaluation, and early warning for grouting curtain effectiveness. In the future, mine curtain grouting will become an important mine geological guarantee technology for safety, efficiency, accurate, sustainability, and green mining of the Earth’s deep resources.

Experimental Study of Slurry Flow in Mining-Induced Fractures during Longwall Overburden Grout Injection

Slurry flow in mining-induced overburden fractures is an important theoretical concept for the grouting design of longwall overburden grout injection engineering. In this study, a visual experimental simulation system of longwall overburden grouting was designed to study the flow, pressure distribution, consolidation, and fill thickness of fly ash slurry in overburden bedding separation. Experiments showed that the slurry generates a radial and bidirectional flow during nonpressure grouting and presents itself as an approximately elliptical dominant flow channel under pressure injection. This channel expanded horizontally along the strike direction and gradually became tabular. The slurry pressure increased as the grouting time increased. Although the pressure curves at different locations exhibited similar trends, their values did not decrease as the distance from the borehole center decreased during observations. Bleeding and consolidation occurred in the slurry as soon as it flowed out of the borehole to the fracture, and the degree of consolidation increased as a function of the distance from the injection borehole. The bleeding water gathered continually to the boundary of the bedding separation fracture and was then seeped to and stored by the underlying strata based on the injection pressure. The final injection fill is manifested as a half pace with a large thickness at the center. This research provides a theoretical basis for the design and optimization of overburden grout injection in underground longwall mining.

A numerical study of the influence of cyclic grouting and consolidation using TOUGH2

With the rapid development of deep underground engineering, grouting technology is widely used to enhance the stability of the surrounding rocks in tunnels, where ingress water, large site disturbance, and deformation are the main challenges. In this paper, a three-dimensional (3D) numerical grouting system, which is based on TOUGH2 and the finite element method (FEM), is developed to study the diffusion and consolidation of grout slurry during the cyclic grouting process. It is observed that the grouting technology can reduce the rock permeability and porosity, increase the degree of compactness, and improve the strength of the rock mass. This numerical grouting system is validated by three numerical tests. The grout diffusion and consolidation process are investigated by simulating grouting experiments. Finally, a detailed mining tunnel grouting schedule is designed, and the corresponding numerical model is established to mimic stopping the water ingress. The results show that the grouting system presented in this study is potentially useful to improve the grout characteristics and tunnel designs, as well as construction.

A laminar box apparatus for 1g testing of granular columns embedded in soft clay

Ordinary stone columns and geosynthetic-encased columns are widely used as a method of soil improvement for soft clay deposits. The behaviour of encased and unencased columns under the action of dynamic loads are not thoroughly understood. In order to shed light into the dynamic behaviour of granular columns and column-enhanced soft soil deposits, a novel large-scale laminar box assembly is designed together with provisions for instrumentation, consolidation of clay slurry and casing pipe pushing units for column installation. The laminar box is comprised of 16 individually supported laminates. The laminar box has inner areal footprint dimensions of 900 × 900 mm and a height of 1932 mm. The laminar box is utilised to study the behaviour of granular columns of varying reinforcement stiffnesses under dynamic loads. In order to make a thorough comparison of reinforcement stiffnesses on column behaviour, columns with different reinforcement arrangements are installed together in the same clay bed, and scaled earthquake accelerograms and sinusoidal base excitations are applied. Column response is studied through the reinforcement strains occurring on the encasement and the amount of vertical pressure sustained on the column during the dynamic load cases.

Examination of the Effects of Solids Content on Thickened Gold Mine Tailings Sedimentation and Self-Weight Consolidation

Abstract Thickening is being increasingly adopted by the mining industry because of its economic and environmental attributes, such as decreased amounts of water released following deposition and a smaller footprint of the tailings site. This study presents an assessment of the continuous process of sedimentation and the self-weight consolidation of slurry and thickened mine tailings. The results of a series of settling column tests performed with specimens with solids contents between 50 % and 72 % are presented and discussed. Lower solids contents that are more characteristic of slurry tailings were also included to cover a wide range of settling behavior. High-precision monitoring of pore water pressure was used to identify the transition from sedimentation to self-weight consolidation, which likely occurs between solids contents of 65 % and 68 % for this material, and it highlighted the fact that the combination of these two settlement processes accelerates ue dissipation. The displacement results for the tailings–water interface corroborate values in the technical literature related to the settlement of suspensions. Equilibrium was reached within a narrow time range (i.e., 400 to 500 min) despite the wide range of initial solids content in the slurries tested (i.e., 50 % S to 65 % S).

Influence of High Voltage Gradients on Electrokinetic Dewatering for Wenzhou Clay Slurry Improvement

Laboratory experiments were conducted to examine the feasibility and determine the optimal voltage gradient of electrokinetic consolidation of Wenzhou clay slurry with a small amount of fine sand. During the process of electrokinetic dewatering using high voltage gradients of 0.5-1.25 V/cm, the current, temperature, drainage, evaporated water, and electrolytic water were monitored in real-time. The results showed that a steady current was achieved under relatively lower voltage gradients (0.5 V/cm), while higher voltage gradients (1 V/cm) reduced the drainage time. Voltage gradients greater than 1.0 V/cm had no significant effect on the drainage rate. A greater reduction in temperature was achieved under higher voltage gradients than using lower voltage gradients, and the evaporated water and electrolytic water increased with increasing voltage gradient. Taken together, the results of this study can be used to optimize engineering practices during land reclamation efforts.

Microstructural effects of the reduction step in reactive consolidation of manganese cobaltite coatings on Crofer 22 APU

The microstructural effects of the reduction step in the reactive consolidation of slurry processed Mn1·5Co1·5O4 coated Crofer 22 APU were studied using cross-sectional scanning and transmission electron microscopies. Alloy samples were coated with a Mn1·5Co1·5O4 slurry and then reduced in moist H2 based forming gas at 850°C for 4 h. The reduced coating contained particles of MnO with the NaCl structure and Co with the face centred cubic (FCC) structure. The interface exhibited a thin dense chromia layer with a thicker porous MnCr2O4 overlayer with needle-like protrusions into the reduced coating. Evidence for inter-reactions during the concurrent coating reduction and substrate oxidation include Co rich metallic inclusions in the spinel layer and an enrichment of the spinel in Mn with distance from the chromia layer. The consequences of these observations for the complex microstructural variation during subsequent reoxidation and long term thermal exposure are discussed.

Rapid starch consolidation of red clay-based ceramic slurry under simultaneous pressure-cooking and microwave irradiation

This study presents a simultaneous application of pressure cooking and microwave irradiation to consolidate ceramic slurry as a rapid shaping technique. The ceramic slurry, composed of red clay, feldspar, quartz and water, was solidified with the gelatinization of starch under varying heating conditions inside a domestic microwave pressure cooker. It was found out that, for a small amount of ceramic slurry, a shortest heating time of 2.52min was achieved at microwave pressure cooking conditions of 50% power level and target temperature of 60°C. Based on these conditions, large shaped ceramic prototypes of different shapes were successfully formed using proposed empirical equations to determine a desired heating time at any power levels. The physical characterizations revealed that the physical properties of dried and fired ceramic bodies formed under microwave pressure cooking were better than that of the conventional counterpart. Microstructural investigation into the fired samples revealed larger void spaces in conventional sample than that in microwave pressure-cooked sample.

Starch consolidation of red clay-based ceramic slurry inside a pressure-cooking system

The consolidation of red clay-based slurry by gelatinization of starch in a domestic pressure cooker was presented. Aqueous ceramic slurries were prepared consisting of a ternary powder mixture of red clay, quartz, feldspar, and different starch types. The starch slurries with and without the presence of ceramic particles demonstrated the same gelling mechanism and heating time inside the pressure cooker. The gel strengths of pressure-cooked samples were higher than samples heated conventionally. Subsequently, the shaping of large ceramic prototypes is possible using a calculated heating time based on best pressure cooking conditions. The physical characterizations disclosed that the pressure-cooked ceramic samples in dried and fired states exhibited better physical properties depending upon the type of starch added in the ceramic slurry. Specifically, the compressive strengths of fired ceramic bodies shaped in the pressure cooker ranged from 82 ± 2 to 255 ± 9 MPa with bulk porosities of 29.0 ± 0.8-18.7 ± 0.2%, whereas the conventionally shaped bodies possessed compressive strengths ranging from 138 ± 8 to 164 ± 11 MPa with bulk porosities of 25.6 ± 0.1-28.5 ± 0.2%.

Experimental evidence for intraplate deformation controlled by netlike plastic-flow in central-eastern Asia

The experimental results of brittle/ductile two-layer analogue models verify that intraplate tectonic deformation in central-eastern Asia is controlled mainly by the netlike plastic-flow (NPF) occurring in the lower lithosphere, including the lower crust and lithospheric mantle. The ductile lower layer in the model, corresponding to the lower lithosphere in the natural prototype, is made of a mixture of gum rosin and turpentine oil and the brittle upper one, to the upper crust, is formed by the consolidation of talc-powder slurry. The NPF hypothesis for continental dynamics can be regarded as a combination and development of two kinds of seemingly mutually exclusive ones, which are based on the theories of slip-line field and viscous (plastic) flow, respectively. In contrast to “homogeneous” viscous (plastic) flow considered usually in fluid mechanics and rheology, NPF is a viscous (plastic) flow accompanied with shear strain localization, forming plastic-flow network in the flow field. Plastic-flow network, being composed of two families of plastic-flow belts intersecting each other with their initial conjugate angles (i.e. the included angles facing the compression direction) equal to 90°, is similar to but different from the traditional slip-line network, which is assumed as a critical state of yield in elastoplastic medium. The experiments show that there are several NPF-controlled tectonic network systems to be developed in the models and two of them correspond to those in central-eastern Asia, which have the Himalayan and Taiwan arcs as their driving boundaries, respectively. The existence of “stable blocks” in the ductile lower layer has promoted some types of tectonic deformation, including the formation of large-scale compressional basins, corresponding to the Tarim, Ordos, Sichuan basins, etc., the development of compression-shear tectonic zones between some of these basins, corresponding to those shown by the Tianshan and Altay mountain ranges, and the uplift of some areas of the “plateau”, corresponding to a contribution to the formation of the Qinghai-Tibet plateau. The distributions of maximum compressive stress directions and strains in the ductile lower layer estimated using the “conjugate-angle-bisector” and “conjugate-angle-increment” methods, respectively, are coincident in general tendency and framework with those in the prototype for the major part of the central-eastern Asian continent. It is also inferred that the westward influence of the horizontal compression component of the Pacific plate has reached North China by means of the interaction between adjacent plastic-flow networks although the tectonic network resulting directly from this horizontal compression has not spread westward beyond the Japan Sea.

Processing Characteristics of Thermoplastic Sheet Composites

Abstract While there are several alternatives for producing thermoplastic sheet composites, only two have the characteristics needed for large scale manufacturing; continuous melt impregnation, and deposition of a polymer-impregnated, fiber-dispersed mat from an aqueous slurry. The most important factor affecting the melt impregnation process was found to be the rate of penetration of the molten polymer into the fiber structure. While Darcy's Law, using the Kozeny-Carmen permeation coefficient, provides an initial estimate of penetration rate, it does not adequately consider the slow flow around closely spaced fibers. The slurry deposition process incorporates the polymer directly within the fiber structure, and is not flow rate limited. The most important parameter affecting the consolidation of slurry formed mats was found to be the rate of heat transfer prior to consolidation. In both processes the time of contact between the molten polymer and glass fiber was shown to be important to the development of good adhesion.

A Cohesive Soil for Large-Size Laboratory Deposits

Abstract The preparation of high-quality, large-size cohesive soil deposits is possible using the slurry method and is practicable if a suitable soil material is used. The requirements for such a soil are discussed and the results of a survey of available ingredient materials presented. A testing program of six trial soil mixtures is described, including consolidation of slurry in a special apparatus. Each trial soil is evaluated, and detailed properties of the selected material, called Cornell clay, are presented. The results from a series of CIUC triaxial tests show that Cornell clay has normalized strength parameters similar to many naturally occurring cohesive soils. Supply sources for the ingredient materials are given.

Drum Centrifuge for Geotechnical Research

Abstract The use of a drum centrifuge for geotechnical research is described. This type of centrifuge is distinguished by its ability to carry a payload around the entire circumference of a rotating drum. This allows the formation of “endless” slopes and gives the centrifuge a large capacity at very low cost. The design and construction of the centrifuge is described in detail. Also, the test procedures used to conduct slope stability experiments, including consolidation of a clay slurry, in-flight cutting of the slope, and both short- and long-term stability tests are discussed. Deviations from true similarity, between model and prototype are listed, including fluctuation in acceleration, variation in water content, and stress paths. Possible future uses of the drum centrifuge are presented.