Development and Application of an in Situ Penetrator for Rapid Strength Testing of Submarine Sediment

In marine engineering, the strength of a submarine sediment is an indispensable parameter for assessment of construction. In this study, a free-fall cone penetrator named IPen was developed to realize a rapid and efficient measurement of sediment strength. The equipment is characterized by modular design and self-contained data acquisition. It is equipped with an acceleration sensor, a water pressure sensor, and a piezocone penetration test(CPTu) probe. It is designed to be released from near seabed surface with a releaser and then fall freely to provide a higher penetration velocity. Its maximum working depth is approximately 2500 m and maximum penetration depth is approximately 3 m. To derive the correlation between penetration resistance and sediment strength, a calibrator was devised to determine the penetration-rate factor. In addition, the factor applicable to in situ test points was determined in laboratory experiments. In June 2016, the IPen was tested in situ in the South Yellow Sea, China, during a shared voyage funded by the National Science Foundation. Meanwhile, undisturbed column samples were collected for laboratory tests. Based on the in situ test results, it was demonstrated that the IPen could accurately record the working states of various sensors during the freely falling course. IPen test results reliably reflected the sediment strength at all the testing points when compared with laboratory calibration tests, in situ vane tests and penetration tests, laboratory penetration tests, and unconsolidated and undrained triaxial compression tests.

温度应力路径对原状海洋土强度特性影响研究

室内温度和海底原位温度的差异导致传统测量所得海洋土物理力学参数存在一定差异。基于温控三轴仪,对我国南海原状海洋土进行了固结不排水剪切试验,实测了海洋土体变、强度、孔压以及模量的变化,探讨温度、温度循环、围压、超固结比等因素对原状海洋土力学性质的影响规律。试验结果表明:升温梯度增大会使正常固结海洋土热固结程度增大,其对应的排水体积和强度也增大;升温对超固结海洋土的排水体积具有增强作用,而温度降低了海洋土的强度;温度循环作用对超固结海洋土的排水体积具有增强作用,其对应的强度也增大;本文试验条件下,当OCR=1时,海洋土25℃下不排水抗剪强度测量结果比5℃下测量结果提高8.0%;当OCR=4时,海洋土25℃下不排水抗剪强度测量结果比5℃下测量结果降低1.9%;经过温度循环5℃—45℃—5℃后的抗剪强度比5℃提高了11.9%;4次或10次温度循环后分别提高了13.8%和17.8%。

Properties of Alkali-activated Yellow River Sediment-slag Composite Material

In order to consume the Yellow River sediment as much as possible and improve the longterm stability of the Yellow River, Yellow River sediment was utilized as the main raw material to produce a composite material. Ca(OH)_2 was used as alkali-activator to activate the active SiO_2 and Al_2O_3 compositions in Yellow River sediment. 10 wt% slag was added into the mixture to further improve the strength of the composites. The effect of activity rate of the Yellow River sediment and dosage of Ca(OH) _2 on the compressive strength of the Yellow River sediment-slag composite material at different curing ages was researched. XRD, SEM/EDS, light microscope and FTIR were used to further explore the products and the microstructure of the composite material. Results showed that the active ratio of sediment had a great influence on the compressive strength of specimen. In addition, the compressive strength of specimen increased with the increase of Ca(OH)_2dosage and curing age. When the dosage of Ca(OH)_2 was more than 5 wt% as well as the curing age reached 90 days, the compressive strength of the composite material could meet the engineering requirement. In the alkali-activated process, the main product was hydrated calcium silicate(C-S-H) gel, which filled up the gaps among the sediment particles and decreased the porosity of the specimen. Moreover, the CaCO_3 produced by the carbonization of the C-S-H gel and excess Ca(OH)_2 also played a role on the strength.

Mechanical properties of gas hydrate-bearing sediments during hydrate dissociation

The changes in the mechanical properties of gas hydrate-bearing sediments(GHBS) induced by gas hydrate(GH) dissociation are essential to the evaluation of GH exploration and stratum instabilities. Previous studies present substantial mechanical data and constitutive models for GHBS at a given GH saturation under the non-dissociated condition. In this paper, GHBS was formed by the gas saturated method, GH was dissociated by depressurization until the GH saturation reached different dissociation degrees. The stress–strain curves were measured using triaxial tests at a same pore gas pressure and different confining pressures. The results show that the shear strength decreases progressively by 30%–90% of the initial value with GH dissociation, and the modulus decreases by 50% –75%. Simplified relationships for the modulus, cohesion, and internal friction angle with GH dissociated saturation were presented.

Mechanical Property and Microstructure of Alkali-activated Yellow River Sediment-Coal Slime Ash Composites

This work focuses on the production of a new composite material using Yellow River sediment and coal slime ash via alkali-activating method. XRD, FTIR and SEM/EDS were used to characterize the alkali-activated products and microstructure of the composite material. Compressive strength was tested to characterize the mechanical property of the composite material. It is found that the compressive strength of the Yellow River sediment-coal slime ash composites increases as the added Ca（OH）_2 content grows. The compressive strength increases fast in the early stage but slowly after 28 days. The strength of the composites can be significantly improved via the addition of small amount of Na OH and gypsum. The products（C-S-H, ettringite and CaCO_3）, especially C-S-H, make much contribution to the enhancement of strength. The highest strength of the composites can reach 14.4 MPa after 90 days curing with 5% Ca（OH）_2, 0.2% NaOH and 7.5% gypsum. The improved properties of the composites show great potential of utilizing Yellow River sediment for inexpensive construction materials.

Mechanical Properties of Methane Hydrate-Bearing Interlayered Sediments

The complex distribution of gas hydrate in sediments makes understanding the mechanical properties of hydrate-bearing sediments a challenging task.The mechanical behaviors of hydrate-bearing interlayered sediments are still poorly known.A series of triaxial shearing tests were conducted to investigate the strength parameters and deformation properties of methane hydrate-bearing interlayered sediments at the effective pressure of 1 MPa.The results indicate that the stress-strain curves of hydrate-bearing interlayered sediments are significantly different from that of hydrate-bearing sediments.The peak strength,Young's modulus,initial yielding modulus,and failure mode are deeply affected by the methane hydrate distribution.The failure behaviors and mechanism of strain softening and hardening patterns of the interlayered specimens are more complicated than those of the integrated specimens.This study compares the different mechanical behaviors between integrated and interlayered specimens containing gas hydrate,which can serve as a reference for the prediction and analysis of the deformation behaviors of natural gas hydrate reservoirs.

混凝土灌注桩施工质量的心法十要研究

研究目的:对于铁路桥涵混凝土灌注桩的施工,由于局部临界软弱土层的坍塌以及影响施工质量的因素预判不准,导致部分灌注桩施工质量不合格,返工处理浪费严重,须采取有效预防措施,确保灌注桩施工质量;由此提出其预防措施的用心统领实施有效方法的十个要点,简称“心法十要”,并对其进行研究。研究结论:(1)心法十要:原材料进场以规定为要;配合比以试验为要;混凝土灌注以控制坍落度为要;软弱地层以控制桩扩径为要;导管位置以控制埋深为要;桩底以控制沉渣厚度为要;桩中以控制混凝土连续为要;桩顶以控制抗压强度为要;完整性检测以最佳处理为要;整个过程以协调为要;(2)心法十要的实施使灌注桩均达合格,可避免返工浪费;(3)本研究成果可为铁路、公路等领域提高混凝土灌注桩施工质量提供参考。

Geotechnical properties of oceanic sediments in polymetallic nodules belts

Geotechnical data obtained from the polymetallic nodules investigation in 1994, in combi nation with the historical data concerned, are analyses comprehensively to study sediment types, geotechnical properties, soil strength and so on, in order to provide bases for design and construction of engineering facilities and the equipments raquired for the polymetallic nodules mining in the future.

Conditional and unconditional QTLs mapping of gluten strength in common wheat (Triticum aestivum L.)

Dissecting the genetic relationships among gluten-related traits is important for high quality wheat breeding. Quantita- tive trait loci （QTLs） analysis for gluten strength, as measured by sedimentation volume （SV） and gluten index （GI）, was performed using the QTLNetwork 2.0 software. Recombinant inbred lines （RILs） derived from the winter wheat varieties Shannong 01-35xGaocheng 9411 were used for the study. A total of seven additive QTLs for gluten strength were identi- fied using an unconditional analysis. QGi1D-13 and QSv1D-14 were detected through unconditional and conditional QTLs mapping, which explained 9.15-45.08% of the phenotypic variation. QTLs only identified under conditional QTL mapping were located in three marker intervals： WPT-3743-GLU-D1 （1D）, WPT-7001-WMC258 （1B）, and WPT-8682-WPT-5562 （1B）. Six pairs of epistatic QTLs distributed nine chromosomes were identified. Of these, two main effect QTLs （QGi1D-13 and QSvlD-14） and 12 pairs of epistatic QTLs were involved in interactions with the environment. The results indicated that chromosomes 1B and 1D are important for the improvement of gluten strength in common wheat. The combination of conditional and unconditional QTLs mapping could be useful for a better understanding of the interdependence of different traits at the QTL molecular level.

水库底泥制备透水混凝土的抗压强度及透水性能

为提高水库底泥在建筑材料领域的附加值利用率,将水库底泥作辅助胶凝材料制备透水混凝土,发现水库底泥掺量的增加会使试件抗压强度下降,透水性能提高;机械活化时间的延长会使试件抗压强度增大,透水性能降低。当水灰比为0.3、机械活化时间为45 min时,制备的水库底泥透水混凝土28 d抗压强度可达21.44 MPa,透水系数为0.56 mm/s。该研究为水库底泥在建筑材料领域的资源化利用提供了参考。

Quick Clay Development and Cation Composition of Pore Water in Marine Sediments from the Ariake Bay Area, Japan

By analyzing the cation composition of pore water in the soil samples of Ariake Bay sediments, the present study assesses the development of quick clay by leaching in both the original and seawater-saturated soil samples. Divalent cations were dominant in the pore water of the original soil sample, whereas Na+ was the major cation in that of the seawater-saturated soil sample. The cation proportion in the pore water for both soil samples remained the same after leaching. The difference in pore water cation composition between the original and seawater-saturated soil samples affected how their geotechnical properties changed through leaching. The undisturbed shear strength of both soil samples remained almost the same, but a large disparity between the soil samples was observed in the remolded shear strength: it remained almost the same in the original soil sample after leaching. Hence, sensitivity was not increased and quick clay was not formed. However, in the seawater-saturated soil sample, the remolded shear strength decreased to a great extent, and quick clay with a sensitivity exceeding 700 developed. The lack of development of quick clay in the original soil sample is attributed to the dominance of divalent cations in the pore water, and the development of quick clay in the seawater-saturated soil sample is ascribed to the dominance of Na+ in the pore water.

复掺再生粗骨料-活性矿物料疏浚底泥透水砖的制备

以河道疏浚底泥为原材料,复掺再生粗骨料-活性矿物料制备疏浚底泥透水砖,通过正交试验研究再生粗骨料、活性矿物料对疏浚底泥透水砖抗压性能、透水性能的影响。结果表明,复掺再生粗骨料和粉煤灰时,疏浚底泥透水砖的最优配合比为:河道疏浚底泥20%、黏土20%、水泥10%、再生粗骨料20%、粉煤灰15%、水15%,按此配比制得的疏浚底泥透水砖抗压强度为36.05MPa,透水系数为1.22×10^(-2)cm/s;复掺再生粗骨料和硅灰时,疏浚底泥透水砖的最优配合比为:河道疏浚底泥20%、黏土20%、水泥10%、再生粗骨料20%、硅灰15%、水15%,按此配比制得的疏浚底泥透水砖抗压强度为36.89 MPa,透水系数为1.26×10^(-2)cm/s。

不同植物对黄土边坡产流产沙与抗剪强度的影响

[目的]探讨不同草本植物对黄土边坡产流产沙与抗剪强度特征的影响,为进一步开展高寒干旱和半干旱地区,有效防治因降雨诱发水土流失、浅层滑坡等地质灾害,提供理论依据和实际指导。[方法]在西宁盆地长岭沟流域自建试验区,选取垂穗披碱草(Elymus nutans)、老芒麦(Elymus sibiricus)、细茎冰草(Agropyron trachycaulum)3种优势草本植物为试验供试种,开展原位人工模拟降雨试验与室内直剪试验,分析了模拟降雨条件下6种不同类型植物边坡坡面产流产沙及根—土复合体抗剪强度特征。[结果]在模拟降雨条件下,草本植物能显著抑制坡面产流产沙,阶梯形边坡相对直形边坡能显著降低坡面产流产沙,且随着草本生长期增加坡面产流产沙显著降低,生长期为2 a的种植垂穂披碱草阶梯形边坡坡面累积产沙量较垂穂披碱草直形边坡降幅为79.68%,生长期为1 a的种植垂穂披碱草阶梯形边坡平均产沙率较阶梯形未种植裸坡降低幅度最大为86.27%,表明种植垂穂披碱草阶梯形边坡有效抑制坡面的产流能力相对显著;进一步研究表明,降雨使边坡土体平均含水率增大,导致边坡浅层土体黏聚力降低;与直形边坡相比较,模拟降雨后阶梯形边坡黏聚力c值降低幅度较小,其中种植垂穂披碱草阶梯形边坡较降雨前降低幅度为19.25%,表明垂穂披碱草阶梯形边坡其增强边坡土体强度效果相对最显著。[结论]垂穗披碱草阶梯形边坡表现出相对更显著的抑制边坡水土流失和提高边坡浅层土体抗剪强度,起到增强边坡土体稳定性的作用。

湖底淤泥固化土的环境耐久性研究

为了评价淤泥固化土的环境耐久性,采用矿渣体系的碱激发胶凝材料(矿渣粉、偏高岭土、石灰和水玻璃)和普通硅酸盐水泥为固化剂,通过开展无侧限抗压、冻融循环、Na2SO4及NaCl浸泡侵蚀、扫描电镜和EDS-Mapping试验,分析了侵蚀环境下固化淤泥土的典型水化产物、强度演变规律、质量损失率和微观结构特征,结果表明,碱激发固化淤泥内部生成的水化硅铝酸钠凝胶(N-A-S-H)能有效提高强度,但是冻融循环和浸泡侵蚀均会导致固化土强度劣化;水泥固化淤泥受硫酸盐侵蚀后,钙矾石会呈现簇状发展而产生膨胀开裂,导致强度下降;碱激发固化剂的抗氯离子能力优于硫酸根离子,综合环境耐久性优于普通硅酸盐水泥。

加气对水肥混合液细小泥沙絮凝沉降的影响

为探明加气对水肥一体化滴灌管网中泥沙沉降能力的影响,配置6种粒径泥沙和3种类型肥料(硫酸钾肥、复合肥、尿素,质量分数均为1.0%)组合的浑水,测定3种水流剪切强度(0,1.38和4.67 s^(-1))条件下加气前后的浑水浊度、泥沙中值沉速和沉降泥沙中值粒径.结果表明:加气加速水肥混合液中细小泥沙的絮凝沉降,尿素水肥混合液加气后泥沙中值沉速增幅最大,硫酸钾肥次之,复合肥最小,分别比未加气处理最高增加89.27%,52.74%和45.63%;加气加速泥沙絮凝沉降的作用随泥沙粒径的减小而增大,加气显著促进中值粒径D≤31μm泥沙的絮凝(P<0.05),沉降泥沙粒径较未加气处理增大3.22%~21.99%,加气显著加速中值粒径D≤53μm泥沙的沉降(P<0.05),中值沉速较未加气处理提高23.96%~89.27%;水流剪切强度越大,加气促进泥沙沉降的作用越小,当水流剪切强度小于4.67 s^(-1)时,加气处理的泥沙中值沉速比未加气处理显著提高9.38%~89.27%(P<0.05).泥沙粒径、肥料种类、水流剪切强度和加气处理相互作用,显著影响浑水泥沙的絮凝沉降,建议水肥气混合液滴灌时应定期冲洗灌溉管网,以减少沉降泥沙.

人工防汛石材的碱激发制备及其抗冻性研究

大块石稀缺是黄河流域防汛抢险的关键问题,而黄河泥沙的资源化利用是解决该问题的重要途径。通过碱激发资源化利用黄河泥沙,采用室内压制成型、现场碾压成型制备人工防汛石材,并用快速冻融法研究人工防汛石材的抗冻性能。采用扫描电镜(SEM)、X射线衍射(XRD)和压汞(MIP)等微观测试方法,研究人工防汛石材形貌、组成和结构的变化,阐明其微观作用机理。研究表明:随着添加剂掺量的增加,人工防汛石材抗压强度呈先提高后降低的趋势;抗压强度、质量、相对动弹性模量随冻融次数的增加而降低,碱激发水泥基人工防汛石材的抗冻性好于碱激发非水泥基人工防汛石材的抗冻性,极限冻融循环次数分别为80和40次;冻融循环不会引起碱激发防汛石材物相的变化,但会导致孔隙率增加,最可几孔径增大。碱激发制备的人工防汛石材具有良好的抗压强度,满足防汛抢险的使用要求。

基于巢湖疏浚底泥的免烧砖制备及其最佳工艺参数研究

基于巢湖疏浚底泥,研究了固化材料种类与掺量、成型压力及加载速率、养护方式对底泥固结体抗压强度的影响,基于最优配合比和工艺参数制备了疏浚底泥免烧砖。结果表明,疏浚底泥固化材料的最佳配合比为:疏浚底泥62.0%、水泥12.5%、生石灰2.5%、粉煤灰2.5%、矿粉7.5%、水12.2%、水玻璃0.8%;最佳成型工艺参数为:成型压力15 MPa,加载速率0.4 mm/s,采用70℃蒸汽养护,制备的疏浚底泥免烧砖吸水率为13.2%,7 d平均抗压强度为18.5 MPa,单块砖最低抗压强度为16.3 MPa,冻融后平均抗压强度为17.1 MPa,单块砖的干质量损失率≤1.6%,符合MU15抗压强度、吸水率和抗冻性的要求。

海底电缆敷设施工悬浮泥沙起悬比研究

由于海上风电海底电缆敷设产生的悬浮泥沙会影响海洋水环境,故悬浮泥沙是海上风电项目环境影响评价的重点之一,目前悬浮泥沙源强的计算采用经验公式,其中起悬比的选取是关键。通过大丰、阳江海上风电项目海底电缆敷设现场浊度实测,推算海底电缆敷设施工产生的悬浮泥沙源强,再通过经验公式反推悬浮泥沙起悬比。结果表明,在底质粒径介于0.011~0.11 mm的粉砂质或淤泥质海域采用水力冲射法进行海底电缆敷设,产生的悬浮泥沙起悬比选取范围在7%~10%之间,该经验为类似项目提供了实测依据。

某细粒铜尾矿絮凝沉降充填性能研究与实践

为了比较某细粒铜尾矿絮凝沉降充填与自然沉降充填效果的差异,在进行了自然沉降和絮凝沉降试验的基础上进行了自然沉降充填与絮凝沉降充填工业实践。结果表明:自然沉降情况下料浆浓度升高,沉降速率降低,底流浓度升高,底流浓度最大可达68%;絮凝剂可显著提高全尾砂沉降速率,浓度为20%的尾矿浆添加20 g/t的PAM,全尾砂沉降速率提高4.66倍,底流浓度下降6个百分点;进料浓度升高,全尾砂絮凝沉降速率降低,底流浓度升高,絮凝沉降底流浓度达55%左右;自然沉降充填体与絮凝沉降充填体相比,有效取芯率、完整性和有效试样数均略逊,2种工艺的充填体有效试样强度均满足充填体强度要求。

成形工艺参数对底泥免烧砖抗压强度的影响

河湖底泥的资源化利用是解决河湖底泥污染治理的关键。本文以巢湖疏浚底泥为研究对象和基料,免烧砖的配合比为疏浚底泥62%、固化剂25%、水13%,其中固化剂的配合比为水泥10.9%、石灰2.5%、矿渣微粉7.5%、粉煤灰2.5%、水玻璃0.5%、无水硫酸钠0.8%、木质素磺酸钙0.3%,采取自然养护,以双面静压成形的方式,研究了不同成形压力、压制速度、恒压时间和搅拌时间对免烧砖力学性能的影响。试验结果表明,免烧砖最优制备工艺参数为:成形压力15MPa,压制速度0.4mm/s,恒压时间为60s;搅拌时间5min。以疏浚底泥为主要原材料,对不同成形工艺生产的底泥免烧砖进行了研究,确定了底泥免烧砖的最佳成形工艺参数,免烧砖7d抗压强度为12.9MPa,强度等级符合免烧砖标准MU7.5,实现了疏浚底泥的资源化利用。