本文關(guān)鍵詞：暴風(fēng)浪作用下海底粉土液化研究　出處：《國(guó)家海洋局第一海洋研究所》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 海底 粉土 液化

【摘要】：粉土廣泛分布在我國(guó)各大河流入�？诟浇�,具有易液化性。海底粉土液化容易引發(fā)海底電纜中斷、海底管道失穩(wěn)和平臺(tái)、立管傾倒等事故,對(duì)海洋工程危害巨大。本文選擇海底地質(zhì)災(zāi)害頻發(fā)的埕島油田海域作為研究區(qū),在前人調(diào)查研究工作的基礎(chǔ)上對(duì)暴風(fēng)浪作用下海底粉土液化開(kāi)展研究工作。前人已調(diào)查發(fā)現(xiàn)此區(qū)域分布著大量的擾動(dòng)土層,并分析證明波浪作用下海底粉土液化是其主要成因。本文在此基礎(chǔ)上,總結(jié)分析了已有的研究區(qū)水動(dòng)力、海底地形地貌及淺地層剖面等資料,搜集了研究區(qū)42個(gè)地質(zhì)鉆孔資料,并按照鉆孔是否位于擾動(dòng)土層內(nèi)對(duì)其分別統(tǒng)計(jì)分析,采用瞬時(shí)液化評(píng)判方法計(jì)算了不同重現(xiàn)期波浪條件下的粉土瞬時(shí)液化深度,根據(jù)風(fēng)生波浪要素及擾動(dòng)土與非擾動(dòng)土的土工試驗(yàn)參數(shù),采用動(dòng)三軸試驗(yàn)評(píng)判方法計(jì)算了擾動(dòng)土與非擾動(dòng)土殘余液化深度,并對(duì)計(jì)算結(jié)果進(jìn)行分析討論。獲得的主要認(rèn)知如下:(1)擾動(dòng)土層內(nèi)部無(wú)明顯層理或?qū)永聿磺?沉積結(jié)構(gòu)雜亂,與非擾動(dòng)土層對(duì)比明顯。相對(duì)于研究區(qū)的非擾動(dòng)土,海底擾動(dòng)土含水量、孔隙比、粘粒含量較小,容重、粉粒含量、中值粒徑及標(biāo)貫擊數(shù)較大,分選較好,土的抗液化能力較強(qiáng)。(2)在50年重現(xiàn)期的波浪作用下,水深8m處海底粉土的瞬時(shí)液化極限深度為1.69m。在其他重現(xiàn)期波浪作用下,海底粉土的瞬時(shí)液化極限深度在水深7m附近達(dá)到最大值。瞬時(shí)液化極限深度總體趨勢(shì)是在某一特定水深處達(dá)到液化深度的最大值。在該水深以淺,土體液化極限深度隨水深增加而增大;在該水深以深,土體液化極限深度隨水深增加而減小。(3)相同風(fēng)浪作用下,擾動(dòng)土的殘余液化深度計(jì)算值比非擾動(dòng)土小。7-10級(jí)風(fēng)作用下,海底表層非擾動(dòng)土出現(xiàn)液化;8級(jí)風(fēng)以上時(shí),海底表層擾動(dòng)土出現(xiàn)液化。不同等級(jí)風(fēng)作用下,最大殘余液化出現(xiàn)深度不同。在暴風(fēng)浪作用下(8級(jí)以上),最大殘余液化深度出現(xiàn)在水深8m-9m處。在10級(jí)風(fēng)作用下,水深8m處非擾動(dòng)土的最大殘余液化計(jì)算深度達(dá)到5.25m,這與物探解譯得到的擾動(dòng)層厚度相吻合。(4)海底粉土最大殘余液化深度的計(jì)算結(jié)果在5m-13m水深處與地球物理探測(cè)結(jié)果基本一致,但在水深3m-4m以及14m以深海底粉土最大液化計(jì)算深度與實(shí)測(cè)資料有所不同。已有物探結(jié)果顯示,3m-4m以及14m以深海底粉土未發(fā)現(xiàn)液化擾動(dòng)層。這樣的計(jì)算結(jié)果主要緣于水動(dòng)力參數(shù)和土體參數(shù)的選取與實(shí)際不一致。
[Abstract]:Silt is widely distributed near the entrance of major rivers in China, which is easy to liquefaction. The liquefaction of subsea silt can easily lead to submarine cable disruption, submarine pipeline instability and platform, toppling of risers, and so on. This paper chooses the sea area of Chengdao Oilfield, which has frequent submarine geological disasters, as the research area. On the basis of previous investigation and research work on the liquefaction of silt under the action of storm wind and wave, it has been found that there are a large number of disturbed soil layers in this area. It is proved that the liquefaction of silt under the action of waves is the main cause of formation. Based on this, this paper summarizes and analyzes the existing data of hydrodynamic, submarine topography and shallow stratum profile in the study area. The data of 42 geological boreholes in the study area were collected and statistically analyzed according to whether the boreholes were located in the disturbed soil layer. The instantaneous liquefaction depth of silt was calculated by using the instantaneous liquefaction evaluation method under the wave conditions of different recurrence periods, according to the wind-induced wave elements and the geotechnical test parameters of disturbed soil and undisturbed soil. The residual liquefaction depth of disturbed and undisturbed soils was calculated by dynamic triaxial test. The main results obtained are as follows: 1) there is no obvious stratification or unclear stratification in disturbed soil layer, and the sedimentary structure is messy. Compared with the undisturbed soil layer, the water content, porosity ratio, clay content, bulk density, silt content, median particle size and standard penetration number of the disturbed soil in the study area are larger, and the separation is better than that of the undisturbed soil in the study area. Under the wave action of 50 years, the instantaneous liquefaction limit depth of the silt is 1.69 m at the depth of 8 m. The instantaneous liquefaction limit depth of subsea silt reaches the maximum near the water depth of 7 m. The general trend of the instantaneous liquefaction limit depth is to reach the maximum liquefaction depth in a specific water depth. The limit depth of soil liquefaction increases with the increase of water depth. Under the same wind and waves, the calculated residual liquefaction depth of disturbed soil is smaller than that of non-disturbed soil. There is liquefaction of undisturbed soil on the surface of seabed. The maximum residual liquefaction depth is different under the action of different grade wind, and the maximum residual liquefaction depth is higher than 8 grade under the action of storm wave. The maximum residual liquefaction depth appears at 8m-9m of water depth, and the maximum residual liquefaction depth of undisturbed soil reaches 5.25m under the action of 10-grade wind. This is consistent with the geophysical results obtained from geophysical interpretation of the maximum residual liquefaction depth of subsea silt in the depth of 5m-13m. But at the depth of 3m-4m and 14m, the calculated depth of maximum liquefaction of deep-sea silt is different from the measured data. No liquefaction disturbance layer was found in 3m-4m and 14m silt. The main reason for this calculation is that the selection of hydrodynamic parameters and soil parameters is inconsistent with the actual conditions.
【學(xué)位授予單位】：國(guó)家海洋局第一海洋研究所
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU411;P75

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