莱州湾西岸工程地质环境及桩基础的适宜性研究
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摘要
莱州湾海域位于山东半岛的北部,是我国一个重要的浅海油气区。随着海域内海上平台、输油管线以及海上人工岛的建设,对莱州湾内工程地质环境需要有一个全面的认识。
本文系统搜集了莱州湾西部海域的气候特征、海洋水文、区域地质、浅部地层等资料对莱州湾西岸区域地壳稳定性、浅部地层工程性质等工程地质环境和桩基在这种地质环境中的适宜性进行了分析。
根据研究区内断裂和地震活动性以及地壳升降速率等特征,综合判断莱州湾西岸区域地壳属次稳定区。表现为以下特点：莱州湾西岸的断裂主要有NNE向、NW向和EW向三组断裂。断裂的最新活动时间是在更新世末期,全新世以来活动性较弱。研究区内未有原发性强震出现,仅有5级左右的中等地震发生。研究区属相对下降区,下降速率在2mm/a左右。
通过多个钻孔分析,莱州湾西岸浅水区受黄河泥沙的影响,上部为现代黄河三角洲侧缘沉积,顶层为粉土,下伏淤泥与粉质粘土互层。该层多为软塑到流塑状态,含水量高、压缩性高、强度小、承压性低,工程性质较差。中间为一套海相沉积层,为粉土与粉质粘土互层,工程性质优于上部。底部为一套陆相沉积,砂粒含量增大,抗剪强度较高。浅水区内浅地层呈粉土层与粉质粘土层互层,垂向上岩性多变,交错叠置,特别是上部普遍存在着淤泥层和淤泥质粉质粘土等,可能造成上部构筑物的不稳定,往往易发生不均匀下沉。经粉土液化分析,浅水区内粉土层不易发生液化。深水区表层为棕色粘土,为一套浅海相沉积,含水量高,抗剪强度低。中间为一套岩性为褐灰色粉砂的陆相沉积层。该层厚度大,抗剪强度高,工程性质良好。下部为褐灰色粉质粘土与粉砂或砂质粉砂互层,由于固结压密作用使得该层抗剪强度很高。
运用AHP—模糊综合评判,采用“适宜”、“较适宜”、“较不适宜”和“不适宜”4级评价体系,建立了10项评价指标对研究区桩基适宜性进行分析。研究表明,研究区内工程地质环境适宜海上平台的桩基施工与稳定。影响桩基适宜性的因素主要是冬季海冰、风暴潮以及地层中的软弱夹层。
The Laizhou Bay located in the northern part of Shandong Peninsula is one of the important shallow sea oil and gas regions. With the constraction of offshore platform, oil pipelines and artificial islands, it is need for a comprehensive understanding of the engineering geological environment of the Laizhou Bay.
Through systemly collecting the material of the characters of climate, marine hydrology, regional geology and shallow stratigraphy, etc, this article analysis the engineering geological environment, which contents the regional crustal stability, the engineering geological characters of shallow stratigraphy and geologic hazard, and the suitability of pile foundation of the weastern Laizhou Bay.
The results of this study are as follows:the stability of the study area's crust is substable according to the activities of the faults and earthquake and the lifting rate of crust, etc.
Coastal area of western Laizhou Bay influenced by the sediment of the Yellow River, the upper part is the modern Yellow River deltatic sedimentation, which the top floor is silt, underlied with silt and silty clay interbedded strata. This part has bed engineering geological characters with high water content, high compressibility, low shear strength and soft plastic-flow plastic. At the middle of shallow stratigraphy the engineering geological characters of marine facies that silt and silty clay interbedded strata is better than upper's. The land facies at the bottom has the best engineering geological characters that the content of sand increased obviously. The silty soil in coastal area less prone to liquefaction according to liquefaction analysis.
Less affected by the Yellow River, the upper part in deep sea is brown clay, reflecting the offshore sediments, which with high water content and low shear strength. The brown-gray land facies silty sand underlied the upper part has the fine engineering geological character that thick layer and high shear strength. At the bottom of the stratigraphy that silty sand or sandy silt interbedded have the vert high shear strength.
Analysised by the AHP-Fuzzy Comprehensive Evluation Method engineering geological environment of the stuty area suitable for the construction and stability of the pile foundation of offshore platforms that influenced by sea ice, storm surges and weak interbed.
本文系统搜集了莱州湾西部海域的气候特征、海洋水文、区域地质、浅部地层等资料对莱州湾西岸区域地壳稳定性、浅部地层工程性质等工程地质环境和桩基在这种地质环境中的适宜性进行了分析。
根据研究区内断裂和地震活动性以及地壳升降速率等特征,综合判断莱州湾西岸区域地壳属次稳定区。表现为以下特点：莱州湾西岸的断裂主要有NNE向、NW向和EW向三组断裂。断裂的最新活动时间是在更新世末期,全新世以来活动性较弱。研究区内未有原发性强震出现,仅有5级左右的中等地震发生。研究区属相对下降区,下降速率在2mm/a左右。
通过多个钻孔分析,莱州湾西岸浅水区受黄河泥沙的影响,上部为现代黄河三角洲侧缘沉积,顶层为粉土,下伏淤泥与粉质粘土互层。该层多为软塑到流塑状态,含水量高、压缩性高、强度小、承压性低,工程性质较差。中间为一套海相沉积层,为粉土与粉质粘土互层,工程性质优于上部。底部为一套陆相沉积,砂粒含量增大,抗剪强度较高。浅水区内浅地层呈粉土层与粉质粘土层互层,垂向上岩性多变,交错叠置,特别是上部普遍存在着淤泥层和淤泥质粉质粘土等,可能造成上部构筑物的不稳定,往往易发生不均匀下沉。经粉土液化分析,浅水区内粉土层不易发生液化。深水区表层为棕色粘土,为一套浅海相沉积,含水量高,抗剪强度低。中间为一套岩性为褐灰色粉砂的陆相沉积层。该层厚度大,抗剪强度高,工程性质良好。下部为褐灰色粉质粘土与粉砂或砂质粉砂互层,由于固结压密作用使得该层抗剪强度很高。
运用AHP—模糊综合评判,采用“适宜”、“较适宜”、“较不适宜”和“不适宜”4级评价体系,建立了10项评价指标对研究区桩基适宜性进行分析。研究表明,研究区内工程地质环境适宜海上平台的桩基施工与稳定。影响桩基适宜性的因素主要是冬季海冰、风暴潮以及地层中的软弱夹层。
The Laizhou Bay located in the northern part of Shandong Peninsula is one of the important shallow sea oil and gas regions. With the constraction of offshore platform, oil pipelines and artificial islands, it is need for a comprehensive understanding of the engineering geological environment of the Laizhou Bay.
Through systemly collecting the material of the characters of climate, marine hydrology, regional geology and shallow stratigraphy, etc, this article analysis the engineering geological environment, which contents the regional crustal stability, the engineering geological characters of shallow stratigraphy and geologic hazard, and the suitability of pile foundation of the weastern Laizhou Bay.
The results of this study are as follows:the stability of the study area's crust is substable according to the activities of the faults and earthquake and the lifting rate of crust, etc.
Coastal area of western Laizhou Bay influenced by the sediment of the Yellow River, the upper part is the modern Yellow River deltatic sedimentation, which the top floor is silt, underlied with silt and silty clay interbedded strata. This part has bed engineering geological characters with high water content, high compressibility, low shear strength and soft plastic-flow plastic. At the middle of shallow stratigraphy the engineering geological characters of marine facies that silt and silty clay interbedded strata is better than upper's. The land facies at the bottom has the best engineering geological characters that the content of sand increased obviously. The silty soil in coastal area less prone to liquefaction according to liquefaction analysis.
Less affected by the Yellow River, the upper part in deep sea is brown clay, reflecting the offshore sediments, which with high water content and low shear strength. The brown-gray land facies silty sand underlied the upper part has the fine engineering geological character that thick layer and high shear strength. At the bottom of the stratigraphy that silty sand or sandy silt interbedded have the vert high shear strength.
Analysised by the AHP-Fuzzy Comprehensive Evluation Method engineering geological environment of the stuty area suitable for the construction and stability of the pile foundation of offshore platforms that influenced by sea ice, storm surges and weak interbed.
引文
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[2]李春荣,辛仁臣,等.郯庐断裂对青东凹陷古近纪沉积体系的控制.新疆石油地质,2008,29(2)：209-213
[3]彭文绪,辛仁臣,等.渤海海域莱州湾凹陷的形成和演化.石油学报,2009,30(5)：654-660
[4]唐辉明.工程地质学基础.北京：化学工业出版社,2008
[5]郑继民.中国海洋工程地质研究.工程地质学报,1994,2(1)
[6]李兴唐,许冰,等.区域地壳稳定性研究理论与方法.北京：地质出版社,1987
[7]孙叶,谭成轩,等.中国区域地壳稳定性定量化评价与分区.地质力学学报,1997,3(3)
[8]田德培,王兰化,王丽瑛.环渤海地区区域地壳稳定性分区与评价.地质调查与研究,2005,28(1)
[9]贾永刚,史文君,单红仙,等.黄河口粉土强度丧失与恢复过程现场振动试验研究.岩土力学,2005,26(3)
[10]张建民,单红仙,贾永刚,等.波浪和潮波作用下黄河口快速沉积海床土非均匀固结试验研究.岩土力学,2007,28(7)
[11]李广雪,庄克琳,姜玉池.黄河三角洲沉积体的工程不稳定性.海洋地质与第四纪地质,2000,20(2)
[12]Li G X, Liu S Q, etal. Primary study on the diaper in the north of the Yellow River delta. Science in China,1999,42 (2)
[13]吴建政.山东全新世滨海软土与工程地质灾害研究.海洋地质与第四纪地质,1995,15(3)
[14]冯秀丽,沈渭铨,等.现代黄河口区沉积环境与沉积物工程性质的关系.中国海洋大学学报,1994,专辑
[15]冯秀丽,林霖,庄振业,等.现代黄河水下三角洲全新世以来土层岩土工程参数与沉积环境之间的关系.海岸工程,1999,18(4)
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