紡錘形樁靴基礎(chǔ)在雙層地基中的穿透破壞特性試驗研究
發(fā)布時間：2018-07-20 20:46
【摘要】：隨著海洋石油、天然氣資源的開采,自升式海洋平臺的應(yīng)用日趨普遍。自升式海洋平臺結(jié)構(gòu)的支撐體系為位于平臺底部三個相互獨立的樁腿,每根樁腿靠獨立的紡錘形樁靴基礎(chǔ)支撐在海床上。海洋平臺的安全性能與紡錘基礎(chǔ)的承載力有著直接的聯(lián)系,因此對紡錘基礎(chǔ)承載特性的研究受到越來越多學(xué)者的關(guān)注。海洋地基通常由砂土覆蓋黏土雙層地基組成。紡錘基礎(chǔ)在此類地基中,當(dāng)上部荷載超過臨界值時,基礎(chǔ)快速刺入下部黏土層,發(fā)生穿透破壞。穿透破壞發(fā)生時間很短,可引起海洋平臺的傾覆,造成巨大的經(jīng)濟(jì)損失。因此研究紡錘形樁靴基礎(chǔ)在此種地基形式下的貫入特性至關(guān)重要。本文在總結(jié)以往學(xué)者研究成果的基礎(chǔ)上,進(jìn)行了多組物理模型試驗,研究了砂土地基、砂土覆蓋黏土層地基形式中紡錘基礎(chǔ)的貫入特性。本文開展的主要研究工作如下：(1)砂土地基模型的制備：模型試驗中,砂雨法為最常用的成樣方法。常規(guī)砂雨法能制備出中密、密實狀態(tài)的砂樣,松散砂樣的制備較為困難。為獲得相對密實度范圍更大的砂樣,利用自主研發(fā)的撒砂裝置,在討論常規(guī)影響因素如流量、落距等的基礎(chǔ)上進(jìn)一步研究了出砂頭移動速度、篩網(wǎng)層數(shù)、出砂頭移動路徑等因素對砂樣相對密實度的影響。通過改變這些控制因素制出了松散狀態(tài)的砂樣。分別通過不同大小的圓盒與CPT方法對砂樣的均勻性進(jìn)行檢測,檢測結(jié)果表明,制備出的砂樣均勻性較好。分析對比不同的均勻性檢測方法,圓盒檢測方法簡單易操作,但檢測結(jié)果誤差較大；CPT方法較為可靠。(2)砂土地基中的物理模型試驗：在進(jìn)行上砂下黏雙層地基中的離心貫入試驗之前,首先進(jìn)行了多組1g室內(nèi)與離心狀態(tài)下的貫入試驗。研究了砂土地基中砂土相對密實度、基礎(chǔ)直徑、基礎(chǔ)形式對貫入特性的影響。結(jié)果表明,隨著砂土相對密實度及基礎(chǔ)直徑的增大,貫入阻力增大。1g試驗中觀測了基礎(chǔ)貫入過程中的土表位移變化,給出了貫入時的影響范圍大小。(3)紡錘形樁靴基礎(chǔ)在上砂下黏雙層地基中易發(fā)生穿透破壞。在砂土地基貫入試驗的基礎(chǔ)上進(jìn)行了多組上砂下黏雙層地基中的離心模型試驗。研究了基礎(chǔ)直徑、砂層的相對密實度、黏土層不排水抗剪強度、砂層相對厚度、加載方式等因素對貫入特性的影響。在此基礎(chǔ)上探討了應(yīng)力控制加載模式下基礎(chǔ)的刺穿破壞速率。結(jié)果表明：砂層相對厚度、基礎(chǔ)直徑、黏土層強度是影響峰值貫入應(yīng)力的關(guān)鍵因素。應(yīng)力控制加載條件下,基礎(chǔ)發(fā)生穿透破壞的速率較大,歷時較短,且黏土層強度越低,破壞時的刺穿速率越大。不同的加載方式下,基礎(chǔ)的貫入特性曲線并無顯著差異。
[Abstract]:With the exploitation of offshore oil and natural gas resources, the application of jack-up offshore platform is becoming more and more common. The supporting system of the jack-up offshore platform is three independent pile legs at the bottom of the platform, each of which is supported on the seabed by independent spindle pile boot foundation. The safety performance of offshore platforms is directly related to the bearing capacity of spindles, so more and more scholars pay attention to the research of the bearing characteristics of spindles. The ocean foundation is usually composed of sand-covered clay double-layer foundation. In this kind of foundation, when the upper load exceeds the critical value, the foundation rapidly penetrates into the lower clay layer and breaks through. The time of penetrating damage is very short, which can cause the overturn of offshore platform and cause huge economic losses. Therefore, it is very important to study the penetration characteristics of spindle-shaped pile boot foundation under this kind of foundation form. On the basis of summing up the previous research results, this paper has carried out many sets of physical model tests, and studied the penetration characteristics of the spindle foundation in the form of sandy soil foundation and sandy soil covered clay layer foundation. The main work of this paper is as follows: (1) preparation of sand soil foundation model: sand rain method is the most commonly used sampling method in model test. It is difficult to prepare loose sand samples with medium density and dense state by conventional sand rain method. In order to obtain sand samples with larger relative compactness, the sand head moving speed and the number of screen layers are further studied on the basis of discussing the conventional influencing factors, such as flow rate and drop distance, using the self-developed sand sprinkler. The influence of the moving path of sand production head on the relative compactness of sand sample. Loose sand samples are produced by changing these control factors. The uniformity of sand samples was tested by circular box and CPT method with different sizes. The results showed that the uniformity of sand samples prepared was good. By analyzing and comparing different homogeneity detection methods, the circular box detection method is simple and easy to operate, but the error of the test result is large. CPT method is more reliable. (2) physical model test in sand soil foundation: before the centrifugal penetration test of upper sand and bottom viscous double layer foundation, several groups of penetration tests were carried out in laboratory and centrifuge state. The influences of relative compactness, foundation diameter and foundation form on the penetration characteristics of sand foundation are studied. The results show that with the increase of the relative compactness of sand and the diameter of foundation, the displacement of soil surface is observed in the process of foundation penetration with the increase of penetration resistance. The influence range of penetration time is given. (3) Spindle pile shoe foundation is easy to break through in upper sand and bottom clay double layer foundation. On the basis of the penetration test of sand soil foundation, centrifuge model tests were carried out in multiple groups of upper sand and bottom clay bilayer foundation. The influence of the diameter of foundation, the relative compactness of sand layer, the undrained shear strength of clay layer, the relative thickness of sand layer and the loading mode on the penetration characteristics are studied. On this basis, the puncture failure rate of the foundation under stress-controlled loading mode is discussed. The results show that the relative thickness of sand layer, the diameter of foundation and the strength of clay layer are the key factors affecting the peak penetration stress. Under stress-controlled loading condition, the penetration rate of foundation is larger, the time is shorter, and the lower the strength of clay layer is, the higher the puncture rate is. Under different loading modes, there is no significant difference in the penetration characteristic curve of the foundation.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U674.381
本文編號：2134728
[Abstract]:With the exploitation of offshore oil and natural gas resources, the application of jack-up offshore platform is becoming more and more common. The supporting system of the jack-up offshore platform is three independent pile legs at the bottom of the platform, each of which is supported on the seabed by independent spindle pile boot foundation. The safety performance of offshore platforms is directly related to the bearing capacity of spindles, so more and more scholars pay attention to the research of the bearing characteristics of spindles. The ocean foundation is usually composed of sand-covered clay double-layer foundation. In this kind of foundation, when the upper load exceeds the critical value, the foundation rapidly penetrates into the lower clay layer and breaks through. The time of penetrating damage is very short, which can cause the overturn of offshore platform and cause huge economic losses. Therefore, it is very important to study the penetration characteristics of spindle-shaped pile boot foundation under this kind of foundation form. On the basis of summing up the previous research results, this paper has carried out many sets of physical model tests, and studied the penetration characteristics of the spindle foundation in the form of sandy soil foundation and sandy soil covered clay layer foundation. The main work of this paper is as follows: (1) preparation of sand soil foundation model: sand rain method is the most commonly used sampling method in model test. It is difficult to prepare loose sand samples with medium density and dense state by conventional sand rain method. In order to obtain sand samples with larger relative compactness, the sand head moving speed and the number of screen layers are further studied on the basis of discussing the conventional influencing factors, such as flow rate and drop distance, using the self-developed sand sprinkler. The influence of the moving path of sand production head on the relative compactness of sand sample. Loose sand samples are produced by changing these control factors. The uniformity of sand samples was tested by circular box and CPT method with different sizes. The results showed that the uniformity of sand samples prepared was good. By analyzing and comparing different homogeneity detection methods, the circular box detection method is simple and easy to operate, but the error of the test result is large. CPT method is more reliable. (2) physical model test in sand soil foundation: before the centrifugal penetration test of upper sand and bottom viscous double layer foundation, several groups of penetration tests were carried out in laboratory and centrifuge state. The influences of relative compactness, foundation diameter and foundation form on the penetration characteristics of sand foundation are studied. The results show that with the increase of the relative compactness of sand and the diameter of foundation, the displacement of soil surface is observed in the process of foundation penetration with the increase of penetration resistance. The influence range of penetration time is given. (3) Spindle pile shoe foundation is easy to break through in upper sand and bottom clay double layer foundation. On the basis of the penetration test of sand soil foundation, centrifuge model tests were carried out in multiple groups of upper sand and bottom clay bilayer foundation. The influence of the diameter of foundation, the relative compactness of sand layer, the undrained shear strength of clay layer, the relative thickness of sand layer and the loading mode on the penetration characteristics are studied. On this basis, the puncture failure rate of the foundation under stress-controlled loading mode is discussed. The results show that the relative thickness of sand layer, the diameter of foundation and the strength of clay layer are the key factors affecting the peak penetration stress. Under stress-controlled loading condition, the penetration rate of foundation is larger, the time is shorter, and the lower the strength of clay layer is, the higher the puncture rate is. Under different loading modes, there is no significant difference in the penetration characteristic curve of the foundation.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U674.381
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相關(guān)期刊論文 前2條
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2 曾虹靜;王忠濤;羅強;欒茂田;郭瑩;;自制砂土裝樣設(shè)備及其控制要素分析[J];人民長江;2012年11期
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