Pore pressure observation: pressure response of probe penetration and tides

Excess pore water pressure is an important parameter that can be used to analyze certain physical characteristics of sediment.In this paper,the excess pore water pressure of subseafloor sediment and its variation with tidal movement was measured following the installation of a wharf in Qingdao,China by using a fiber Bragg grating(FBG)piezometer.The results indicated that this FBG piezometer is effective in the field.The measured variation of excess pore water pressure after installation is largely explained by the dissipation of excess pore water pressure.The dissipation rate can be used to estimate the horizontal consolidation coefficient,which ranged from 1.3×10^–6 m^2/s to 8.1×10^–6 m^2/s.The measured values during tidal phases are associated with the variability of tidal pressure on the seafloor and can be used to estimate the compressibility and the permeability of the sediment during tidal movement.The volume compression coefficient estimated from tidal oscillation was approximately 2.0×10^–11 Pa^–1,which was consistent with the data from the laboratory test.The findings of this paper can provide useful information for in situ investigations of subseafloor sediment.

Chloride ion penetration into concrete under hydraulic pressure

The lining concrete of subsea tunnel services under combined hydraulic pressure, mechanical and environmental loads. The chloride ion and water penetrations into concrete under hydraulic pressure were investigated. The experimental results indicate that the water penetration depth, chloride ion transportation depth, and the concentration of chloride ion ingression into concrete increase with raised hydraulic pressure and hold press period. But the chloride ion transportation velocity is only 53% of that of water when concrete specimens are under hydraulic pressure. The chloride transportation coefficient of concrete decreases with hold press period as power function. And that would increase 500% 600% in chloride transportation coefficient when the hydraulic pressure increases from 0 to 1.2 MPa. The hydraulic pressure also decreases the bound chloride ion of concrete to about zero. Besides, the low water-cementitions materials and suitable content of mineral admixture(including fly ash and slag) improve the resistance capacity of chloride penetration, and binding capacity of concrete under hydraulic pressure.

Experimental confirmation of physical metal penetration generation and press casting production considering molten metal's pressure control

This paper presents a technique for controlling the pressure of a molten metal when using a new type of iron casting method called sand mold press casting to realize high productivity and obtain high-quality products.The past test results using this method showed a casting yield of 90% to 95%,while conventional methods only show a casting yield of 60% to 70%.Although the press casting method does not require a sprue cup or runner channel casting defects such as metal penetration are often caused by the high pressure in the high-velocity pressing part of this casting process.Therefore,we proposed a pressure control method with a mathematical model of molten metal pressure,and with it we achieved experimental confirmation of the successful production of brake drums at different pressing temperatures.Results show that the proposed pressing control method can realize sound,penetration-free casting production.However,the theoretical analysis and design of this pressing process had not previously been studied sufficiently,and therefore this paper presents the theoretical design algorithm for the process as well as its experimental confirmation.

Research on the Critical Buckling Pressure of Bucket Foundations with Inner Compartments for Offshore Wind Turbines

In the process of suction penetration of bucket foundations with inner compartments for offshore wind turbines,most researches focus on soil seepage failure and soil plugs,while the buckling of foundations is rarely investigated.Therefore,theoretical calculation methods for critical buckling pressures of the skirt and bulkheads of the bucket foundation are first presented according to the stability theory of a cylindrical shell and the small deflection theory of a thin plate,respectively.Furthermore,two types of models with and without considering the skirt-soil interaction are developed for the calculation of critical buckling pressure of the bucket foundation.Taking a practical project as an example,theoretical and numerical methods are used to obtain the critical buckling pressures of a bucket foundation.In this work,the theoretical method and the finite element model considering the skirt-soil interaction for calculating the critical buckling pressure of bucket foundations are firstly proposed.The results can help to optimize the design process of offshore wind turbine foundations and improve the safety of offshore wind power systems.

Dynamic effects of high-pressure pulsed water jet in low-permeability coal seams

Mine gas extraction in China is difficult due to the characteristics such as micro-porosity,low-permeability and high adsorption of coal seams.The pulsed mechanismof a high-pressure pulsed water jet was studied through theoretical analysis,experimentand field measurement.The results show that high-pressure pulsed water jet has threedynamic properties.What's more,the three dynamic effects can be found in low-permeabilitycoal seams.A new pulsed water jet with 200-1 000 Hz oscillation frequency andpeak pressure 2.5 times than average pressure was introduced.During bubble collapsing,sound vibration and instantaneous high pressures over 100 MPa enhanced the cuttingability of the high-pressure jet.Through high-pressure pulsed water jet drilling and slotting,the exposure area of coal bodies was greatly enlarged and pressure of the coal seamsrapidly decreased.Therefore,the permeability of coal seams was improved and gas absorptionrate also decreased.Application results show that gas adsorption rate decreasedby 30%-40%and the penetrability coefficient increased 100 times.This proves that high-pressurepulsed water is more efficient than other conventional methods.

Determination of the maximum allowable gas pressure for an underground gas storage salt cavern——A case study of Jintan,China

Increasing the allowable gas pressure of underground gas storage(UGS) is one of the most effective methods to increase its working gas capacity. In this context, hydraulic fracturing tests are implemented on the target formation for the UGS construction of Jintan salt caverns, China, in order to obtain the minimum principal in situ stress and the fracture breakdown pressure. Based on the test results, the maximum allowable gas pressure of the Jintan UGS salt cavern is calibrated. To determine the maximum allowable gas pressure, KING-1 and KING-2 caverns are used as examples. A three-dimensional(3D)geomechanical model is established based on the sonar data of the two caverns with respect to the features of the target formation. New criteria for evaluating gas penetration failure and gas seepage are proposed. Results show that the maximum allowable gas pressure of the Jintan UGS salt cavern can be increased from 17 MPa to 18 MPa(i.e. a gradient of about 18 k Pa/m at the casing shoe depth). Based on numerical results, a field test with increasing maximum gas pressure to 18 MPa has been carried out in KING-1 cavern. Microseismic monitoring has been conducted during the test to evaluate the safety of the rock mass around the cavern. Field monitoring data show that KING-1 cavern is safe globally when the maximum gas pressure is increased from 17 MPa to 18 MPa. This shows that the geomechanical model and criteria proposed in this context for evaluating the maximum allowable gas pressure are reliable.

Research on the nonlinear spherical percolation model with quadratic pressure gradient and its percolation characteristics

For bottom water reservoir and the reservoir with a thick oil formation, there exists partial penetration completion well and when the well products the oil flow in the porous media takes on spherical percolation. The nonlinear spheri-cal flow equation with the quadratic gradient term is deduced in detail based on the mass conservation principle, and then it is found that the linear percolation is the approximation and simplification of nonlinear percolation. The nonlinear spherical percolation physical and mathematical model under different external boundaries is established, considering the ef-fect of wellbore storage. By variable substitu-tion, the flow equation is linearized, then the Laplace space analytic solution under different external boundaries is obtained and the real space solution is also gotten by use of the nu-merical inversion, so the pressure and the pressure derivative bi-logarithmic nonlinear spherical percolation type curves are drawn up at last. The characteristics of the nonlinear spherical percolation are analyzed, and it is found that the new nonlinear percolation type curves are evidently different from linear per-colation type curves in shape and characteris-tics, the pressure curve and pressure derivative curve of nonlinear percolation deviate from those of linear percolation. The theoretical off-set of the pressure and the pressure derivative between the linear and the nonlinear solution are analyzed, and it is also found that the in-fluence of the quadratic pressure gradient is very distinct, especially for the low permeabil-ity and heavy oil reservoirs. The influence of the non-linear term upon the spreading of pressure is very distinct on the process of percolation, and the nonlinear percolation law stands for the actual oil percolation law in res-ervoir, therefore the research on nonlinear per-colation theory should be strengthened and reinforced.

Penetration Resistance of Skirt-Tip with Rough Base for Suction Caissons in Clay

Suction caissons can readily penetrate into the seabed under the combination of the self-weight and suction resulted from the encased water being increasingly pumped out. During suction-assisted penetration, the equivalent overburden at the skirt-tip level outside the caisson is generally higher than that inside because the vertical stress within the soil plug is reduced by the exerted suction. This may result in a uniform shear stress developing over the base of the skirt-tip as the soil below the skirt-tip tends to move into the caisson, which leads to an asymmetric failure wedge existing below the base of the skirt-tip. Besides, different adhesion factors along the inside(αi) and outside(αo) of the skirt wall will cause asymmetric plastic zones inside and outside the caisson. Accordingly, an asymmetric failure mechanism is therefore proposed to calculate the penetration resistance of the skirt-tip. The proposed failure mechanism is the first to consider the effect of different adhesion factors(αi) and(αo) on the failure mechanism at the skirt-tip, and involves the contribution from the weighted average of equivalent overburdens inside and outside caisson at the skirt-tip level. The required suction pressure can be obtained in terms of force equilibrium of the caisson in a vertical direction. Finally, the asymmetric failure mechanism at the skirt-tip is validated with the FE calculations. By comparing with the measured data, the predictions of the required suction pressure are found to be in good agreement with the experimental results.

Penetration Resistance of Composite Bucket Foundation with Eccentric Load for Offshore Wind Turbines

The penetration of the composite bucket foundation(CBF)is crucial in its construction process.In actual projects,the foundation is inevitably subjected to eccentric load caused by towers and turbines,as well as wind,wave,and flow,during the one-step installation.Moreover,the eccentric load is bound to affect the penetration method and penetration resistance of the foundation.To examine the above-mentioned issues,the penetration resistance of CBF with eccentric load was calculated and analyzed based on model tests,and the seepage field of the CBF under eccentric load was analyzed using ABAQUS.The influence of different magnitudes of eccentric load and various offset strategies on penetration resistance was analyzed,and the theoretical and measured values were compared.The result indicated that the negative pressure of the offset room was found to be smaller than that of other rooms when the CBF penetrated the soil under eccentric load.The penetration resistance of CBF under eccentric load was larger than that without eccentricity,and the larger the eccentric load is,the greater the penetration resistance.The influence of different eccentric load offset strategies on penetration resistance was found to be negligible.The calculated penetration resistance under eccentric load was in good agreement with the measured value.

Evaluation of Shear Strength and Cone Penetration Resistance Behavior of Tropical Silt Loam Soil under Uni-Axial Compression

Laboratory investigations were conducted to study strength characteristics of silt loam soil of Ilorin, Kwara State, Nigeria, under uni-axial compression tests. The main objective of this study was to evaluate the effects of applied pressure and moisture content on strength indices such as bulk density, penetration resistance and shear strength of the soil and to develop relationships between the strength indices for predictive purposes necessary in soil management. The compression was carried out at different moisture contents determined according to the consistency limits of the soil. The applied pressure ranged from 75 to 600 kPa. Values of bulk density, penetration resistance and shear strength increased with increase in moisture content up to peak values after which the values decreased with further increase in moisture content. Regression models were used to describe the trends in the results for the soil. Results also showed that bulk density and soil strength normally regarded as indicators of soil quality are affected by moisture content and applied pressure and that these properties can be predicted using the models generated from the study.

流动点法表征润滑脂流动性与传统评定方法相关性研究

为建立更完善、高效的轴承润滑脂流动性能评价体系,采用旋转流变仪、润滑脂和石油脂锥入度试验器、润滑脂相似黏度试验器、FFK低温流压仪测试了锂基润滑脂、脲基润滑脂和磺酸钙基润滑脂3种不同稠化剂类型的润滑脂的流动点、锥入度、相似黏度和流动压力,分别研究了锂基润滑脂、脲基润滑脂和磺酸钙基润滑脂3种不同稠化剂的流动点与锥入度、流动点与相似黏度、流动点与流动压力随温度的变化规律并分别计算了它们的皮尔逊相关系数,结果显示润滑脂的流动点与锥入度、流动点与相似黏度、流动点与流动压力具有线性关系,其中流动点与锥入度呈中等相关,流动点与相似黏度、流动点与流动压力呈高度相关,说明利用旋转流变仪测定润滑脂的流动点亦可用于评价润滑脂的流动性能.

万米深井钻柱减振增能提速方法研究

万米深井超深超长井段钻进过程中存在钻柱振动剧烈、能量传递困难、破岩效率低、钻头使用寿命短等问题,亟需开展万米深井钻柱减振与井底增能技术研究。根据超深层钻井环境的主要特征,结合近年来钻柱动力学研究结果,提出了以钻井过程中钻柱振动为能量来源提高井底钻井液射流压力的方法,在减小钻柱振动保护钻头的同时,提高钻头射流压力,实现井下增能破岩,解决井下振动强度大、井底水力能量不足的问题;并研制了井底钻柱减振增能装置,进行了现场试验。研究和试验结果表明:钻柱振动蕴含巨大的能量,该能量可以转化为破岩提速能量;设计的井底钻柱减振增能装置,可以提高钻井液射流压力,同时可以降低钻柱振动导致的安全风险,从而显著提高钻井速度。研究成果为万米深井减振提速技术开拓了新方向,为加快深部油气资源的勘探与开发提供了技术支持。

经皮吸收促进剂用量对压敏胶黏附性的影响

目的探讨经皮吸收促进剂(简称促透剂)用量对透皮贴剂中压敏胶黏附性的影响。方法选择Plurol■Oleique CC497为模型促透剂,两种不同内聚力聚丙烯酸酯压敏胶为模型压敏胶,制备不同促透剂用量的贴剂,测定初黏力、持黏力、180°剥离强度和流变学参数。利用调制差示扫描量热法测定压敏胶玻璃化转变温度;利用红外光谱分析促透剂与压敏胶的相互作用机制。结果随着促透剂用量的增加,两种压敏胶初黏力提高,持黏力下降,高内聚力压敏胶在高促透剂用量下黏附性能仍较好。促透剂的加入会降低压敏胶的玻璃化转变温度,增加压敏胶分子流动性。红外光谱结果显示,Plurol■Oleique CC497与压敏胶间可能发生氢键作用,破坏了压敏胶聚合物分子间的相互作用,使黏附力发生变化。结论促透剂的加入会增加压敏胶的黏附性失效风险,在高促透剂用量下,应选择高内聚力压敏胶制备透皮贴剂。

泥水盾构隧道地层渗透压力的确定及规律研究

泥水盾构隧道施工中的地层渗透压力是设定开挖仓泥水压力等施工参数的主要依据之一。为提高地层渗透压力计算的准确性,开展泥水盾构隧道地层渗透压力的确定方法及规律研究。考虑土体开挖、泥水支护、壁后注浆等施工因素,建立模拟泥水盾构施工动态过程的三维流固耦合模型,分析盾构掘进和同步注浆等施工作业以及地层情况对地层渗透压力的扰动范围和扰动程度,基于此提出泥水盾构隧道地层渗透压力的修正公式。结果表明:当注浆压力为200~500 kPa时,盾构施工对地层渗透压力的最远影响范围为距离开挖面前方4.5环处;在相同注浆压力下,对岩层渗透压力的扰动范围最大,砂土层次之,黏土层最小;采用修正公式得出的地层渗透压力计算值与实测值变化趋势基本一致,验证了修正公式的合理性。

机械扩孔有效抽采半径数值模拟及现场应用

为研究掘进工作面机械扩孔的卸压增透效果,以扩孔后的抽采有效影响半径为考察指标,借助COMSOL-Multiphysics数值模拟软件建立机械扩孔模型,动态分析机械扩孔后的瓦斯流场,拟合得出扩孔有效影响半径与抽采时间的关系曲线;通过理论分析和现场考察试验,类比同等工况条件下机械扩孔与普通钻孔的预抽效果,定量探讨2种施工工艺条件下瓦斯流量衰减系数。研究表明,机械扩孔的瓦斯抽采流量平均值为0.0222 m^(3)/min,最低瓦斯抽采流量是初始抽采流量的56.9%,下降幅度为43.1%;而普通钻孔的瓦斯抽采流量平均值为0.006826 m^(3)/min,最低瓦斯抽采流量是初始抽采流量的22.6%,下降幅度达77.4%。机械扩孔抽采浓度由72%降到38%,降幅为47.2%,普通钻孔抽采浓度由39%降到17%,降幅达56.4%,说明机械扩孔卸压增透效果显著。

工程地质方法在海上风电场勘察中的应用研究

海上风电场类工程项目需要对海底地层结构、土体物理学参数进行测定,研究过程分析了工程地质方法中孔压静力触探试验原理,介绍了设备调试、数据计算的基本方法。再结合具体的风电场项目,对其14#风机建设位置的海底地层开展试验,有效地确定了地层结构,包括淤泥层、粉质黏土层、粉砂层、中砂层,并且计算出各土层的土体饱和重度、压缩模量、有效内摩擦角和相对密实度。

软基处理PST桩复合地基加固机理及CPTU验证

对于厂房、仓库、露天堆场等沿海软土地基加固处理工程,采用传统的软基处理方法如真空预压或堆载预压,其施工工期长、工后沉降大;采用水泥搅拌桩由于施工质量不易控制,桩体强度低、处理效果不佳;采用刚性桩复合地基存在地面堆载沉降不均匀等难题。“PST”复合地基处理方法采用预制桩与桩帽及厚褥垫层组合,将预制桩的高承载力转化为褥垫层均布承载力;地面均布荷载引起的变形应力传递到桩身而非其下的软土。以某大型地基处理工程为例,通过CPTU孔压静力触探技术评价PST桩地基处理加固效果与挤土效应,通过对打桩过程中,不同时期的超静孔隙水压力进行观测,掌握超静孔隙水压力消散和变化规律。通过打桩过程中的超孔压的变化情况,分析打桩顺序和速率对孔压的影响程度,了解PST桩施工对软土的扰动规律,以指导施工,降低PST桩施工对地基土的影响。

某工业仓库地面渗水原因分析及解决方案探讨

通过对某工业包装仓库地面渗水原因的分析,结合地质勘察结果,深入研究地面渗水根本原因,发现地面渗水是由地形高差变化大、地下水位高、基础沉降不均匀、地面垫层分缝变成通缝等原因所致。提出了压力注浆密封、打透水管、建筑周边打渗水井及盲沟、止水帷幕等几种解决办法,通过防排结合综合治理措施取得了较好的效果。

压力容器21/4Cr1Mo1/4V钢深熔TIG焊接工艺

研究压力容器用21/4Cr1Mo1/4V钢深熔TIG焊接工艺,分析不同参数下焊缝的力学性能,通过工艺试验分析深熔TIG焊接中的主要影响因素,提出控制措施,获得良好的焊缝成形和综合力学性能。

A new bleb-independent surgery namely penetrating canaloplasty for corticosteroid-induced glaucoma: a prospective case series

AIM: To report the outcomes of penetrating canaloplasty for corticosteroid-induced glaucoma in a case series.METHODS: Penetrating canaloplasty is a blebindependent filtering surger y unifying canaloplasty and trabeculectomy. In this study, the surger y was performed to restore the natural outflow through surgically expanded Schlemm’s canal and generated trabeculum ostium. A total of 10 eyes of 8 patients were treated with penetrating canaloplasty for corticosteroid-induced glaucoma. Intraocular pressure(IOP) and the number of glaucoma medications at postoperative 3, 6, 12, 18, 24,36, and 48mo were documented as primary endpoint.Complications after the surgery were recorded as secondary endpoint.RESULTS: Penetrating canaloplasty was accomplished successfully for all 10 eyes, with a mean follow-up of 20.4±13.0mo(range 6-48mo). The mean preoperative IOP and number of anti-glaucoma medications were 45.1±6.5 mm Hg and 3.3±0.5 respectively. The mean post-operative IOP at 3, 6, 12, 18, 24, 36, and 48mo were 15.8±6.0, 14.7±3.3,15.3±2.0, 15.6±2.6, 17.5±1.8, 16.5±4.9, and 14.0 mm Hg.The number of anti-glaucoma medications at these time points were all 0. This surgery failed to control the IOP in 1 eye at 1mo after surgery. Hyphaema occurred in 3 eyes on the first day after surgery. Postoperative transient IOP increasing was encountered with in two eyes from 1wk to 1mo after surgery. Choroidal detachment developed in one eye but responded well to conservative treatment.CONCLUSION: Penetrating canaloplasty is effective for corticosteroid-induced glaucoma without serious complications, making it a viable or preferred alternative option.