圖書典藏及影音數位平台

許多結構因地震導致土壤液化而造成之破壞，如日本阪神大地震造成河川防洪堤嚴重受損，因此國外針對基礎軟弱地區的防洪堤，研擬相關土讓液化防治對策，以最近台灣美濃地震後，造成曾文溪日新護岸、尖山堤防破壞，結果顯示係為土壤液化造成堤防破壞。 為進一步瞭解土壤液化防治技術之可靠性及經濟性，針對國內傳統及創新工法進行研究，並提出一個可供國內防洪設施土壤液化防治技術及施工工法，供國內水利相關單位參考使用。

1、Introduction Earthquakes are often accompanied by severe disasters. In particular, the geotechnical structure is damaged caused by soil liquefaction, and many hydraulic facilities are inevitably destroyed. For example, the 2011 Great Hanshin Earthquake in Japan, the 1999 Jiji earthquake, and the 2016 Mino earthquake in Taiwan caused severe damage to many river levee dikes in 2011 caused by soil liquefaction. Therefore, many countries are actively studying the countermeasures of soil liquefaction for flood control levees in vulnerable areas. This project is to study the failure mechanism and prevention techniques for river bank damage caused by soil liquefaction. 2、Literature review The first step of this study is to collect the domestic and international literature, including the case of soil liquefaction leading to river bank damage, liquefaction prevention method, and liquefaction potential analysis, etc. Furthermore, the mechanism and analysis methods of damage to flood control facilities caused by soil liquefaction are discussed. This study reviews the available soil improvement methods and evaluated them in terms of their applicability, economy, durability, safety, and environmental protection Based on the literature review, it is found that the common ground improvement measures for soil liquefaction include pre-consolidation method, grouting method, vibration, and compaction method, etc. However, due to the high cost, time-consuming, and unfriendliness to the environment, traditional construction methods often lead to the high total project cost. Therefore, international scholars are actively seeking for a soil liquefaction prevention method that can improve the site, reduce construction costs, and is environment-friendly. The evaluation of soil liquefaction can be divided into two types: laboratory test method and in-site test method. Laboratory test methods include cyclic triaxial test, cyclic shear test, and cyclic torsional shear test. In-site test methods that can be used to evaluate liquefaction resistance includes SPT, CPT and Vs method, etc. Among these approaches, the SPT-N a most commonly used method in engineering　practice. 3、Damage mechanism of flood control facilities caused by soil liquefaction This study explores the mechanism of soil liquefaction and the failure types of river embankments due to soil liquefaction. The manifestation of soil liquefaction is different due to different slopes of the ground surface. The sand boil occurs in the horizontal surface, lateral spreading appears on the gentle slope, and flow liquefaction occurs on the steep slope. The common types of failure of river dikes are a loss of bearing capacity, flow damage, side collapse, and loss of material in the embankment according to the analysis results. Soil liquefaction occurs when the earthquake-induced cyclic shear stress within the soil layer is greater than the soil liquefaction resistance. In the engineering applications, it is generally defined by the liquefaction safety factor to determine whether the soil layer is liquefied or not. When the FL value is less than 1.0, the soil layer is a liquefied. Soil liquefaction resistance strength can be estimated by the method mentioned previously. Besides, the safety of river embankments against soil liquefaction can be analyzed using quasi-static analysis or dynamic analysis methods. 4、Application of innovative technology for the countermeasure of soil liquefaction in flood control facilities The innovative method selected in this study is a cold aggregation technology, currently under development. The technology uses soil microorganisms in natural metabolism so that the physical properties of soil are changed and then improved so-called mineralization of soil mineralization technology that strengthens soil for liquefaction prevention. The study uses Bacillus pasteurii as a seed of bio-mineralization. Bacillus pasteurii can decompose urea to release ammonia ions and carbon dioxide. Then, the decomposition products interact with calcium ions to induce calcite precipitation, which can bond sand together. The loose sand is aggregated into rock, strengthening or cementing the soil. This method can be applied not only to the construction of new riverbank structures, but also to the ground improvement of existing riverbank structures. However, application of this method to the soil liquefaction prevention for levees is a poineer study internationwide. It is also the first attempt to conduct a field experiment in Taiwan. There are not many research cases and the field experiments have not been verified by multiple variables and reproducable tests. The results of this study in the laboratory have initially confirmed the efficiency of this method for soil liquefaction prevention. Therefore, the results of the field experiments still need to be verified repeatly to confirm the applicability of this method. 5、Model test of the innovative and traditional technology of soil liquefaction prevention for levees The deep mixing method has a high proportion in the use of Portland cement. This is why we select the cement grouting method. It is the easiest way to reduce the simulation in the laboratory in all traditional methods. The method can also be carried out by drip irrigation method, which can be compared with the MICP method. The standard sand specimen without cohesion can be aggregated by the action of microbial-induced carbonate precipitation (MICP). Once the MICP starts in the specimen, the overall aggregation condition improves with the increasing days. The results of the compressive strength test show that the compressive strength of the specimen can be increased from the zero to about 3 to 12 kPa. Whether the traditional method or the MICP method can be used to aggregate the standard sand specimen without cohesion by increasing the strength. Moreover, the specimen with higher relative densities has higher compressive strengths. When the MICP application time is more than 15 days, soil strength grows rapidly. By contrast, the traditional cement grouting method will not increase soil strength once the cement hydration is completed. In the MICP method, however, the compressive strength value will continue increasing with time until the bacterial solution and nutrient solution cannot seepage into the specimen. The results indicate that the MICP method is as effective as the traditional cement grouting method after more than 60 days of reaction. Based on the result of resonance column tests, shear wave velocity of the traditional method after 30 days is lower than that of the MICP method after 15 days. 6、Comprehensive evaluation of traditional and innovative technology for soil liquefaction countermeasure of flood control facilities In order to explore innovative technologies, more thorough evaluations are performed on the feasibility of their prevention for soil liquefaction. The evaluation tasks include the applicability of the MICP construction method to site and foundation improvement, environmental protection, economic durability, and construction safety. MICP has great advantages in construction safety and durability of soil liquefaction prevention. Because the MICP method is environment-friendly, it is safer than the chemical or mechanical construction required with large machines and tools. The stabilization of the MICP method on soil liquefaction prevention continues to increase over time. The calcium carbonate produced by MICP is the same as the component in rock, and, therefore, there is no doubt about its durability. The MICP method has proved an innovative method in the international study. However, more in-situ tests and verifications are needed before application in the engineering practice. 7、The procedure of innovative and traditional technology for soil liquefaction countermeasure of flood control facilities Among these soil liquefaction prevention methods, the deep soil mixing method is an extremely effective method for dealing with weak layers. It uses special machinery to mix the weak soil with the injected solidified material, thus forming a consolidated soil body. When accouting for the characteristics of the object, the size of the structure, the importance, and the economy, the deep mixing method is often considered. The cement grouting technique is a method to fill the cement slurry, cement mortar, chemicals or the above mixture into the gound to improve the bearing capacity of the site. The above two traditional methods are to inject the cemented material into the the ground to strengthen the foundation, similar to the MICP innovation method proposed in this study. Although the deep soil mixing method also uses Portland cement, it requires heavy equipments to mix cement and soil in the deep ground. The manpower, materials, and machinery are expensive, which is not affordable for the small-scale . The cement grouting method by driping is comparable with the MICP method. There are many techniques of soil liquefaction prevention methods (Architecture and Building Research Institute, 2004) According to the research content, a variety of ground improvement methods (such as shallow mixing method, deep mixing method, grouting method, preloading and drainage method, vibration and compaction method, ground freezing method, blasting densification method, etc. is mentioned. In addtion, grouting material, inspection method, validation methods and precautions are spefified. According to the above reference, this study compiled a technical specification for the countermeaure of soil liquefaction in flood control facilities, including into two methods: biological mineralization dripping method and cement grouting method. This technical speficication is applicable to the design of stratum improvement engineering related to the levee failure due to soil liquefaction. However, there are many ground improvement methods, each with its applicable stratum and conditions. Therefore, this technical speficication only proposes a principled proposal for its design. The details of the detailed design and standards of the stratum should be determined by the designer or the contractor based on technical speficication, the soil characteristics of the levee and the engineering requirements. The technical speficication is mainly divided into the following four steps: (1) The data for flood control facilities are collected and analyzed. (2) The liquefaction potential of the flood control facility is identified. (3) The methods of soil liquefaction prevention are determined and prepared prior to soil improvement. (4) After the soil improvement is completed, a verification test is　performed to understand the durability of soil improvement. The factors to be considered include the construction environment, equipment, workers, materials and techniques to be used during the construction. The specific design procedure of innovative technology for soil liquefaction countermeaure of flood control facilities includes the following five steps. (1) Assess the applicability of biomineral dripping methods and materials. (2) Decide the areas of dripping improvement. (3) Estimate the amount of dripping. (4) Configuration of dripping holes. (5) Formulate in-site dripping test and inspection methods for verification of the improvement. 8、In-site test of traditional and innovative technology In this study, the traditional cement grouting method and the innovative MICP method are selected for the real-scale in-site test. The experimental site is selected from the area with high liquefaction potential as disclosed by the central geological survey or the place where liquefaction occurred previously. After collecting and analyzing the basic data, the Ni-Shin revetment in Guantian district, Tainan is selected as the test site. The improved stratum can be roughly divided into silty sand layer and silty clay layer. The gravel are presented in each layer. The artificial structures are encountered from 8 meters to 10 meters below the ground surface. According to the old as-built data, the lower layer of the site may be the old dike structure, and the upper layer is the backfill material containing a number of different sizes of gravel. As a result, the standard penetration test SPT-N value is difficult to interpret due to the refusal. The SPT test, surface wave method and Calcium carbonate production test are used to verify the test results of soil improvement. The MICP field test proves the soil improvement preliminarily. However, due to the scale of the research, the obrained parameters of the verification test are limited. The current test results are still uncertain. It is still necessary to perform test considering a number vairation (such as stratum structure, void content, groundwater depth, etc.). 9、Overlap analysis and evaluation of soil liquefaction potential for flood control facilities This study is based on the preliminary liquefaction potential maps of the central geological survey, including Taipei City, New Taipei City, Kaohsiung City, Yilan County, Hsinchu County, Tainan City, Pingtung County, Taichung City, Changhua County, Yunlin County and Chiayi County. The levee site subjected to liquefaction potential is determined by overlaying the embankment of the river administered by the central government with the liquefaction potential map. The preservation priorities of flood control structures are classified by their importance and protected objects and the liquefaction potential. Finally, the developed soil liquefaction prevention method is applied to these levees identified with high vulnerability. Firstly, the liquefaction potential map published by the central geological survey and the distribution of embankments in each county and city are presented to understand the distribution of embankments associated with the liquefaction potential area. Then, the condition of land use and embankment distribution by each county and city are summarized. Finally, a preliminary classification of river embankment preservation was carried out, and the priority is determined for river embankment with high liquefaction potential. In addition, historical liquefaction sites are presented at the same time to understand the actual liquefaction position and its relationship with the potential diagram. Finally, depending on the level of damages, the order for river embankment preservation is reviewered and modifed again　and could be adopted as a referecne by the water resources agency for soil liquefaction prevention. 10、Establishment of standard operating procedures of soil liquefaction prevention for flood control facilities According to the results of this study, the research and development of soil liquefaction prevention and controlcountermeasure is applied to flood control facilities.