Experimental study on settling velocity of soil particles in dredged slurry

Studying sedimentation and consolidation of dredged slurry has significant implications to the design of storage yard and subsequent ground improvement. In this study, settling velocity of soil particles in dredged slurry during sedimentation and consolidation processes was investigated using an improved multilayer extraction sampling (MES) method. A series of sedimentation column tests were performed on dredged slurry with three different initial water contents. Distributions of volume of soil particles and density of dredged slurry were first obtained by the MES method, settling velocity of soil particles was then calculated by volume flux function approach. It was found that the density and velocity inflection points can be used to distinguish the settling zone and the consolidation zone. The experimental results reveal that the velocity of soil particles was quite low and monotonically decreased with sedimentation height at low initial water content throughout the whole test period, whereas it was increased at 0–1 hours and almost remained constant at 1–7 hours in the settling zone at high initial water content. The effects of initial water content on sedimentation and consolidation mode of dredged slurry and the settling velocity of soil particles were discussed. The relationship between settling velocity of soil particles and particle diameter was also studied. It is indicated that the measured velocity of soil particles was much lower than that calculated by the Stokes equation, and it was related to 0.4881–0.5906 order of particle diameter at 0–1 hours and 0.1117–0.1825 order of particle diameter at 1–7 hours for the test slurries.     

含水率对泥石流浆体力学特性影响实验研究

探讨含水率对泥石流浆体力学特性影响是泥石流运移过程研究的基础性内容。以成都龙泉区黏土为实验材料,配制11种不同含水率的泥浆,利用安东帕MCR301流变仪,对不同含水率泥浆开展两循环旋转剪切实验(每循环剪切过程分为增速剪切(0-30 s^-1)和减速剪切(30-0 s^-1)两阶段),分析含水率对泥浆剪切过程、剪应力变化过程、剪切应力峰值及灵敏度的影响。实验结果表明:①初剪应力峰值和复剪应力峰值与含水率呈幂律关系。②由于剪切过程的差异性导致含水率对泥浆的剪应力与剪切速率的影响也具有差异性:当含水率低于100%时,第一、第二循环各阶段剪切过程中剪切应力变化过程完全不重合,且初剪应力峰值和复剪应力峰值随含水率增大迅速降低,灵敏度随含水率的增加迅速减小到1;当含水率高于100%时,第一、第二循环各阶段剪应力变化过程基本一致,含水率对应力峰值和泥浆灵敏度的影响可以忽略不计。③影响成都黏土泥浆剪切过程、剪切应力变化、剪应力峰值和灵敏度的含水率阈值是100%。本文对成都区黏土泥浆开展了动态剪切试验,探讨了含水率对泥浆特性的影响,可为其他区域黏土特性的研究提供参考,具有重要的研究意义!     

粘度时变浆液的水化机制及其在治理基坑涌水中的应用

SJP型粘时变浆液;水化机制;流变性;基坑涌水     

粘土固化注浆堵水试验研究

论述了粘土（湖泥）固化注浆技术在矿山堵水中的试验研究情况，包括矿区水文地质情况，注浆浆液的配制及性能研究，制浆及注浆施工，质量检查和经济效益分析。     

复杂地层高压旋喷护壁堵漏技术的研究与应用

借鉴复杂地层高压旋喷护壁堵漏技术设计了一种带有特殊喷嘴的旋喷钻具,在复杂地层钻进,尤其是多层段复杂地层和深部复杂地层钻进时,泥浆护壁失效的情况下,将该钻具下到复杂孔段,利用泥浆泵将水泥浆液压入,通过旋喷钻具连续旋转喷射出高压水泥浆切割坍（垮）塌孔段孔壁,使不稳定孔壁的破碎岩土崩落掉块与水泥浆混合,候凝后,在坍（垮）塌孔段形成直径不规则的柱状水泥岩土混合体,重新钻穿后,形成有一定强度的“水泥套管”,从而达到同径护壁堵漏的目的。详细介绍了该项技术的旋喷钻具的设计、水泥浆液配方、工艺原理、技术要点、操作要领及生产应用效果。     

Anatomy of turbidites and linked debrites based on long distance (120 × 30 km) bed correlation, Marnoso Arenacea Formation, Northern Apennines, Italy

Much of our understanding of submarine sediment‐laden density flows that transport very large volumes (ca 1 to 100 km³) of sediment into the deep ocean comes from careful analysis of their deposits. Direct monitoring of these destructive and relatively inaccessible and infrequent flows is problematic. In order to understand how submarine sediment‐laden density flows evolve in space and time, lateral changes within individual flow deposits need to be documented. The geometry of beds and lithofacies intervals can be used to test existing depositional models and to assess the validity of experimental and numerical modelling of submarine flow events. This study of the Miocene Marnoso Arenacea Formation (Italy) provides the most extensive correlation of individual turbidity current and submarine debris flow deposits yet achieved in any ancient sequence. One hundred and nine sections were logged through a ca 30 m thick interval of time‐equivalent strata, between the Contessa Mega Bed and an overlying ‘columbine’ marker bed. Correlations extend for 120 km along the axis of the foreland basin, in a direction parallel to flow, and for 30 km across the foredeep outcrop. As a result of post‐depositional thrust faulting and shortening, this represents an across‐flow distance of over 60 km at the time of deposition. The correlation of beds containing thick (> 40 cm) sandstone intervals are documented. Almost all thick beds extend across the entire outcrop area, most becoming thinly bedded (< 40 cm) in distal sections. Palaeocurrent directions for flow deposits are sub‐parallel and indicate confinement by the lateral margins of the elongate foredeep. Flows were able to traverse the basin in opposing directions, suggesting a basin plain with a very low gradient. Small fractional changes in stratal thickness define several depocentres on either side of the Verghereto (high) area. The extensive bed continuity and limited evidence for flow defection suggest that intrabasinal bathymetric relief was subtle, substantially less than the thickness of flows. Thick beds contain two distinct types of sandstone. Ungraded mud‐rich sandstone intervals record evidence of en masse (debrite) deposition. Graded mud‐poor sandstone intervals are inferred to result from progressive grain‐by‐grain (turbidite) deposition. Clast‐rich muddy sandstone intervals pinch‐out abruptly in downflow and crossflow directions, in a fashion consistent with en masse (debrite) deposition. The tapered shape of mud‐poor sandstone intervals is consistent with an origin through progressive grain‐by‐grain (turbidite) deposition. Most correlated beds comprise both turbidite and debrite sandstone intervals. Intrabed transitions from exclusive turbidite sandstone, to turbidite sandstone overlain by debrite sandstone, are common in the downflow and crossflow directions. This spatial arrangement suggests either: (i) bypass of an initial debris flow past proximal sections, (ii) localized input of debris flows away from available sections, or (iii) generation of debris flows by transformation of turbidity currents on the basin plain because of seafloor erosion and/or abrupt flow deceleration. A single submarine flow event can comprise multiple flow phases and deposit a bed with complex lateral changes between mud‐rich and mud‐poor sandstone.     

沙漠地区大直径顶管施工护壁减阻浆液研究与应用

沙漠地区地层稳定性差,摩阻力大,导致长距离大直径顶管施工时间长,浆液输送压力损失大,极易造成地层垮塌埋管,顶管阻力急剧增加导致顶进失败。沙漠地区大直径顶管工程顺利顶进的关键是浆液应具有较好的润滑减阻和成套护壁作用。基于这一关键问题,开展室内试验和现场应用研究,研发出了适合沙漠地区顶管的新型护壁减阻浆液,采用高岭土聚合物浆液作为机头同步注浆浆液,无粘土高聚物浆液作为沿线跟进补浆浆液。同步注浆浆液在润滑减阻的基础上主要突出成套护壁作用,而跟进补浆浆液主要突出润滑减阻特性,从而使润滑减阻浆液系统达到最佳的润滑和护壁作用。研发的新型护壁减阻浆液应用于内蒙古乌兰布和沙漠穿沙输水项目7～9号顶段——国内外首例沙漠地区大直径顶管工程,效果良好,顶进工作顺利完成。该研究提升了沙漠地区顶管工程关键技术、解决了护壁与减阻问题,具有极大的社会价值和经济效益。     

煤层气井牛顿流体压裂压力损失预测模型

为准确预测牛顿流体连续管压裂作业时沿程管柱内的压力损失,根据我国煤层气井压裂所采用压裂液的特点,运用流体力学理论与方法,建立了基于牛顿流体流变学基本特征的混砂液在连续油管内流动过程中的压力损失预测模型;对不同施工排量、砂比、连续管径和入井长度比等参数对管内压力损失的影响规律进行了分析。提出： a .牛顿流体在管内流动压力损失的主控因素为流体与管壁的摩擦,因此,降低牛顿流体管内压力损失的有效途径是合理选择连续油管直径与优化施工排量; b .为降低管内摩擦压力损失,应参考入井长度比值等参数,合理优选连续油管长度; c .在满足连续管工作压力和保证携砂液性能的前提下,牛顿流体压裂时应尽可能采用大管径、大排量、中砂比施工。     

北京平原区新生界立体地质调查钻探泥浆护壁技术

结合北京市平原区新生界立体地质调查钻探施工工程,阐述了北京平原区第四系取心钻探工程的地层特点、施工技术难点.重点介绍了松散地层不同地层泥浆特性、配比及护壁效果、措施.     

川西南某铅锌矿钻孔护壁堵漏技术

川西南某铅锌矿区地质条件复杂,第四系、基岩风化带和基岩段多以软硬夹层和裂隙发育的岩石为主,局部漏失比较严重。为了解决该区域地层钻孔的漏失问题,笔者在分析地层及现场工艺条件后,提出并设计了采用新型高分子材料马丽散E堵漏剂和水泥浆堵漏技术。该堵漏剂初凝和终凝时间较短,操作过程比较简单,注入孔内后,低粘度混合物能保持液体状态几秒钟或几分钟,能够很好地渗入到地层的细小裂隙中。通过现场漏失钻孔段的实际堵漏验证,该方案可以有效解决地层漏失等问题,减少了辅助时间,降低了工程成本,提高了钻进效率。