竖向高荷载作用下大直径超长钻孔灌注桩承载性能试验     

桑伟锋 《世界地质》2020,39(1):127-134

通过机场—西华高速大直径超长钻孔灌注桩大吨位竖向单桩静载试验,分析了该地区大直径超长钻孔灌注桩的承载性状以及荷载传递机理。试验结果表明:试桩的Q-S曲线呈缓变型,桩端承载力占总荷载的比例均<10%,即均表现为摩擦桩特性;试桩的侧摩阻力自上而下逐步发挥,侧摩阻力和桩端阻力异步发挥且互相耦合;大直径超长钻孔灌注桩桩侧摩阻力的发挥与土层性质、土层埋深及桩顶荷载水平有关;在高荷载作用下桩侧上部土层摩阻力具有不同程度的软化现象,而中下部土层侧摩阻力具有不同程度的强化现象,甚至即使在最大加载情况下,桩身下部土层的侧摩阻力也并未完全发挥,因此在根据规范计算超长桩承载力时,不同深度土层的侧摩阻力应乘以相应不同的修正系数。  相似文献   

Why asymptotic limit of the acid dissolution capacity can lead to a sharp dissolution front in chemical dissolution of porous rocks?          下载免费PDF全文

Chongbin Zhao  B.E. Hobbs  A. Ord 《国际地质力学数值与分析法杂志》2017,41(15):1590-1602

The use of the asymptotic limit can greatly simplify the theoretical analysis of chemical dissolution front instabilities in fluid‐saturated rocks and therefore make it possible to obtain mathematical solutions, which often play a crucial role in understanding the propagation behavior of chemical dissolution fronts in chemical dissolution systems. However, there has been a debate in recent years that the asymptotic limit of the acid dissolution capacity (i.e., the acid dissolution capacity number approaching zero) alone cannot lead to a sharp dissolution front of the Stefan type in the acidization dissolution system, in which the dissolvable minerals of carbonate rocks are chemically dissolved by the injected acid flow. The acid dissolution capacity number is commonly defined as the ratio of the volume of the carbonate rock dissolved by an acid to that of the acid. In this paper, we use four different proof methods, including (i) direct use of the fundamental concepts; (ii) use of the mathematical governing equations of an acidization dissolution system; (iii) use of the different time scaling approach; and (iv) use of a moving coordinate system approach, to demonstrate that the asymptotic limit of the acid dissolution capacity can indeed lead to sharp dissolution fronts of the Stefan type in acidization dissolution systems on a much larger time scale (than the dissolution time scale). Our new finding is that on the reaction time scale, the condition of the conventional time derivative of porosity approaching zero alone can ensure that the acidization dissolution front has a sharp shape of the Stefan type. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Bearing capacity of offshore umbrella suction anchor foundation in silty soil under varying loading modes     

Qi Yang  Guanglai Pan  Quandi Wang 《Marine Georesources & Geotechnology》2018,36(7):781-794

Considering the current disadvantages of present offshore wind turbine foundations, a novel anchor foundation with skirt and branches is proposed, called offshore umbrella suction anchor foundation (USAF). A series of experiments and numerical simulations were performed to explore the bearing capacity of the USAF under various kinds of loading modes. The bearing characteristics and the anchor–soil interactions are described in detail for horizontal static loading, horizontal cyclic loading, and an antidrawing (pullout) test in silty soil. In the static loading test, the load–deflection of the anchor under step loading was analyzed and the normalized curve of the load–deflection was obtained to determine the ultimate horizontal bearing capacity of the anchor under normal working conditions. Under horizontal cyclic loading, the relationship between the plastic cumulative deformation and cyclic number was determined. In addition, the responses of USAF were investigated for a low wave frequency and storm surges. In the drawing test, it was found that a “segmentation phenomenon” occurred during the test. Moreover, a method to identify the maximum antidrawing load of USAF was provided based on dynamic mechanics. The numerical results show that the use of anchor branches and skirt can enhance the bearing performance of USAF to a certain degree. However, the anchor branch has a slight positive influence on the bearing performance improvement. The USAF is not only similar to a stiff short pile, but a rotation occurs. The failure envelope under composite loading (V-M) was obtained and the changes associated with changes in the aspect ratio of the internal compartment were clarified.  相似文献   

利用抗剪强度计算地基承载力特征值方法探讨          下载免费PDF全文

潘广灿  张金来  郜松杰 《探矿工程》2011,38(11):68-70,82

利用不同地层情况的计算实例,分别采用抗剪强度指标厚度加权平均法和附加应力面积法对地基承载力特征值进行计算,对计算结果进行分析,对不同的计算方法的理论原理进行了剖析,提出利用附加应力系数法计算抗剪强度指标标准值的结论。同时提出抗剪强度指标应采用不固结不排水剪指标,当持力层为粉土时应对其抗剪强度指标进行75%的折减的方法和建议。为合理利用抗剪强度指标计算地基承载力特征值提供了有益的参考。  相似文献   

冻土区天然气水合物勘探低温钻井液理论与试验   总被引：3，自引：2，他引：1       下载免费PDF全文

杨葳  杨阳  徐会文 《探矿工程》2011,38(7):29-31,56

天然气水合物是在特定的低温与高压条件下形成的产物。在天然气水合物勘探工作中,低温钻井液是获得天然气水合物真实样品的重要保证条件之一。低温钻井液应具有低的冰点、良好的抵制能力与良好的流动性。结合天然气水合物勘探工作的特点,在试验的基础上,对比分析了PAM、PHPA、PAC-141、Na-CMC与KHm的分子结构、官能团的种类与数量对钻井液的防塌能力和流动性的影响,得出了几种处理剂的耐低温能力大小的顺序为：PAC-141〈PHPA〈PAM〈Na-CMC〈KHm,为天然气水合物勘探中低温钻井液的配制与使用,奠定了重要的基础。  相似文献   

螺杆桩技术设计与施工在长春地区的应用     

李国峰  张德新 《吉林地质》2011,30(3):112-115

本文利用螺杆桩技术对长春地区粘性土层,进行抗拔实验,获得螺杆桩在粘性土层中抗拔承载力值,通过现场抗拔桩试验检测,为螺杆桩技术在长春地区应用提供理论依据,具有重要的理论与实际意义。  相似文献   

横-竖筋带布置对地基影响的试验研究     

侯娟  张孟喜  张陶陶  陈通 《岩土力学》2011,32(8):2365-2370

分别针对纯砂地基、水平加筋地基和新型三维立体加筋(简称横-竖加筋)地基进行了多组模型试验。主要研究了单层横-竖加筋深度和横-竖加筋层数对地基的影响,并通过与水平加筋地基的比较,结合横-竖地基砂土滑移面的形状,初步分析了横-竖加筋地基的加固机制。试验结果表明,同等试验条件下,横-竖筋的加筋效果较水平筋的好,对于单层横-竖加筋地基,加筋效果随加筋深度的增加而减弱,加筋深度超过一定范围后,加筋对地基受力性能的改善不明显。对于多层横-竖加筋地基,随加筋层数的增加,承载力增加,沉降减小。  相似文献   

吉林省三所城市电磁辐射监测结果统计分析与评价   总被引：1，自引：0，他引：1  

高彦伟  王笑晗  张静 《世界地质》2011,30(3):435-438

以城市环境电磁污染为研究对象,根据吉林省长春、延吉、四平环境综合电场强度监测数据．利用统计学方法和指数评价法进行统计分析和评价,计算了三所城市的电磁污染评价指数和污染风险概率,并对环境电磁辐射容量进行了估算。结果表明：目前三所城市环境电磁辐射电场强度监测值具有不同的概率分布,辐射强度低于中国电磁辐射安全标准,污染风险概率为0。如果电磁辐射能量以年均14％的速度递增,长春、延吉、四平将分别在19年、16年和18年后电磁辐射水平超过电磁环境保护限值,因此应该加强城市环境电磁辐射的管理和防控。  相似文献   

基于生态足迹的陕西省适度人口研究   总被引：1，自引：0，他引：1  

徐坡  韩新海 《地下水》2011,33(3):177-181

一个区域生态适度人12的确定取决于区域生态承载力与区域人12对生态资源的需求.首先介绍了生态足迹模型的基本概念和计算方法,其次计算了陕西省1990-2004年的生态足迹和实际利用的生态承载力,并在此基础上估算了陕西省1990～2004年的态适度人口.结果表明:在1990～1998年,陕西省年生态适度人口由2898.9万...  相似文献   

双排抗滑桩中单桩侧向承载实验     

马清文  宋书志  孔纪名 《地质灾害与环境保护》2011,22(3):78-83

通过室内模型实验,研究有无联系梁、联系梁厚度以及排间距对抗滑桩抗滑性能的影响.双排桩组合有联系梁时的抗滑承载力超出无联系梁的40％;联系梁强度能满足变形要求时,其厚度或刚度的增加对加强抗滑性能的作用不大;排间距较小的支护结构侧向承载力较大.  相似文献