本文選題：新近吹填淤泥地基 + 二次處理技術(shù)　； 參考：《華南理工大學(xué)》2015年博士論文

【摘要】：新近吹填淤泥是指原位海積或湖積淤泥經(jīng)水力重塑和顆粒重新分選后、土顆粒自重沉積尚未完成、顆粒結(jié)構(gòu)極松散、含水率極高(85%-150%、甚至大于150%)、處于懸浮狀態(tài)或流動(dòng)狀態(tài)的吹填淤泥。該類地基目前主要采用“二次處理技術(shù)”進(jìn)行加固—即‘先采用淺表層快速加固技術(shù)(屬于無(wú)砂墊層真空預(yù)壓技術(shù))對(duì)新近吹填淤泥地基淺表層土體進(jìn)行預(yù)處理30天的同時(shí),水力吹填厚度為1.0m左右的中(粉)細(xì)砂墊層并機(jī)械鋪設(shè)(吹填)厚度為0.5m左右的中粗砂排水墊層,待真空恒載滿45天后卸載,此時(shí)的地基便能作為承載排水板施工設(shè)備的工作平臺(tái),然后采用傳統(tǒng)真空預(yù)壓技術(shù)或真空聯(lián)合堆載預(yù)壓技術(shù)對(duì)地基深層土體進(jìn)行處理”。新近吹填淤泥地基須進(jìn)行二次處理的主要原因有兩方面：(1)新近吹填淤泥地基承載力為零,無(wú)法直接承受任何地基處理施工機(jī)械設(shè)備(如推土機(jī)、插板機(jī)等)；(2)新近吹填淤泥中黏粒(d≤0.005mm)含量高、白重落淤慢,強(qiáng)親水礦物含量高、土體所吸附的結(jié)合水多。現(xiàn)行規(guī)范中塑料排水板的相關(guān)性能指標(biāo)(包括排水性能指標(biāo)和材料強(qiáng)度指標(biāo))與新近吹填淤泥這種固有的工程特性不相適宜。工程實(shí)踐表明,后一方面的原因直接導(dǎo)致：新近吹填淤泥地基淺表層快速加固過(guò)程中,豎向排水井的淤堵問(wèn)題非常嚴(yán)重,排水效率急劇降低；豎向排水井之間的土體強(qiáng)度很不均勻,土體強(qiáng)度增長(zhǎng)十分有限；地基有效加固深度小、承載力低；地基表面形成許多以豎向排水井為中心的“土柱”,不均勻沉降非常明顯。因此,經(jīng)典的砂井地基固結(jié)理論和目前已有的砂井地基強(qiáng)度增長(zhǎng)計(jì)算方法不完全適用于該類地基。本文首先對(duì)中國(guó)大陸不同區(qū)域的新近吹填淤泥的工程特性進(jìn)行了系統(tǒng)、全面地總結(jié)和分析,并依托實(shí)際工程開(kāi)展了不同形式真空預(yù)壓排水系統(tǒng)現(xiàn)場(chǎng)對(duì)比試驗(yàn)研究,探討了該類地基的負(fù)壓傳遞特性及分布模式,建立了相應(yīng)的真空固結(jié)理論；然后,針對(duì)該類地基的排水固結(jié)特點(diǎn),推導(dǎo)出其土體強(qiáng)度增長(zhǎng)計(jì)算公式,并通過(guò)實(shí)際工程對(duì)其合理性進(jìn)行了驗(yàn)證；最后,針對(duì)上述二次處理的兩方面真正原因,有針對(duì)性地開(kāi)展了試驗(yàn)研究,研發(fā)出了新型大面積砂被墊層工藝技術(shù)和新近吹填淤泥地基加固新技術(shù),為新近吹填淤泥地基成功實(shí)現(xiàn)一次性排水固結(jié)處理的提供了新思路。本文的研究結(jié)論概括如下：(1)中國(guó)大陸不同區(qū)域的新近吹填淤泥是疏浚淤泥處于動(dòng)水沉積階段和靜水沉積階段的產(chǎn)物,沉積于出水口附近及遠(yuǎn)離出水口的區(qū)域,由較細(xì)顆粒物質(zhì)和極細(xì)顆粒物質(zhì)組成,其孔隙特征主要以孤立孔隙和粒間孔隙為主,其微觀結(jié)構(gòu)特征主要以紊流狀和粒狀鑲嵌結(jié)構(gòu)為主。新近吹填淤泥中的黏粒(d0.005mm)含量和強(qiáng)親水礦物(伊利石、蒙脫石)含量都偏高；含水量均大于90%,且均大于1.5倍的液限；孔隙比均大于2.0；塑性指數(shù)基本大于20；液性指數(shù)基本大于2.0。這種極差的工程特性直接致使新近吹填淤泥地基采用傳統(tǒng)真空預(yù)壓技術(shù)加固(包括淺表層快速加固技術(shù))時(shí)的固結(jié)變形特點(diǎn)與一般軟基存在較大的差異,宏觀上主要表現(xiàn)為豎向排水體出現(xiàn)嚴(yán)重的“彎折”現(xiàn)象以及細(xì)土顆粒向豎向排水體周圍移動(dòng)出現(xiàn)嚴(yán)重的“土柱”現(xiàn)象。(2)新近吹填淤泥地基采用傳統(tǒng)真空預(yù)壓技術(shù)(包括淺表層快速加固技術(shù))加固過(guò)程中,整個(gè)排水系統(tǒng)內(nèi)的負(fù)壓損失程度較嚴(yán)重,最嚴(yán)重的高達(dá)57%；負(fù)壓從豎井向其周圍土體傳遞過(guò)程中的損失程度也非常嚴(yán)重,至少為67%。這是新近吹填淤泥地基真空預(yù)壓加固后土體強(qiáng)度增長(zhǎng)有限的主要原因。而且,新近吹填淤泥地基真空預(yù)壓加固過(guò)程中,排水邊界處的負(fù)壓是非均勻分布的,水平排水墊層中的負(fù)壓可考慮為隨時(shí)間變化的線性衰減模式,而豎向排水體中的負(fù)壓可考慮為隨時(shí)間變化的非線性衰減模式�；诖私⒘素�(fù)壓非均勻分布邊界條件下的真空固結(jié)理論,并相應(yīng)地給出了解析解。(3)基于有效應(yīng)力原理和應(yīng)力路徑法對(duì)新近吹填淤泥地基排水固結(jié)的強(qiáng)度增長(zhǎng)機(jī)制進(jìn)行了定性分析,分析結(jié)果表明：地下水位線以上土體的強(qiáng)度增長(zhǎng)規(guī)律和地下水位線以下的土體的強(qiáng)度增長(zhǎng)規(guī)律是不盡相同的。并基于有效應(yīng)力唯一性理論推導(dǎo)出新近吹填淤泥地基排水固結(jié)的強(qiáng)度增長(zhǎng)計(jì)算公式,該計(jì)算公式全面考慮了真空荷載及其沿深度方向的衰減程度、外加荷載、地下水位等因素的影響,且依托實(shí)際工程對(duì)該計(jì)算公式進(jìn)行了驗(yàn)證：按不排水剪強(qiáng)度考慮時(shí),平均誤差為8.0%；而按破壞面上的強(qiáng)度考慮時(shí),平均誤差為3.2%,因此,計(jì)算精度能滿足工程要求。(4)新型大面積砂被工作墊層是一種大型的空間立體式結(jié)構(gòu),為透水性結(jié)構(gòu),包括扁平結(jié)構(gòu)體、側(cè)向復(fù)合式柔性結(jié)構(gòu)體以及柱狀結(jié)構(gòu)體(流泥地基中無(wú)需設(shè)置)。該結(jié)構(gòu)與下臥浮(流)泥地基構(gòu)成一個(gè)整體的、具有較高承載力的承力體系,可以作為深層排水板施工設(shè)備的工作平臺(tái)。該類墊層地基的承載機(jī)理主要體現(xiàn)為：似殼體效應(yīng)(包括應(yīng)力擴(kuò)散效應(yīng)與表層封閉效應(yīng))、側(cè)向封閉效應(yīng)(即側(cè)限作用)、排水固結(jié)作用和豎向加筋作用(流泥地基中無(wú)該項(xiàng)作用)。該類墊層地基的破壞形式呈沖剪破壞特征。方案7(方案7／)(編織土工布規(guī)格為280g/m2)是最佳方案�；谕茖�(dǎo)出的承載力估算公式進(jìn)行計(jì)算可知,方案7/墊層地基的臨塑荷載為Pcr=146.4kPa。該類墊層地基服役過(guò)程中,需要做好插板施工過(guò)程中的清泥措施和排水措施。(5)現(xiàn)行規(guī)范中塑料排水板的相關(guān)性能指標(biāo)(包括排水性能指標(biāo)和材料強(qiáng)度指標(biāo))與高黏粒含量新吹填淤泥固有的工程特性不相適宜、且目前的真空預(yù)壓設(shè)計(jì)時(shí)采用過(guò)快的真空荷載加載速率致使“土柱”現(xiàn)象過(guò)早的形成,這兩方面共同導(dǎo)致了“新近吹填淤泥地基淺表層快速加固后,土體強(qiáng)度增長(zhǎng)有限、有效加固深度小以及承載力仍無(wú)法滿足建設(shè)用地需求。室內(nèi)試驗(yàn)研究結(jié)果表明：新近吹填淤泥地基可采用由中等等效孔徑(如O95為0.15mm)的反濾層和抗彎折性強(qiáng)的芯體組成的豎向排水體作為豎向排水系統(tǒng),以較快的真空荷載加載速率進(jìn)行分級(jí)真空預(yù)壓加固,從而實(shí)現(xiàn)一次性排水固結(jié)處理的目的。
[Abstract]:The newly dredged silt is that the self gravity deposition of the soil particles has not been completed, the particle structure is very loose, the water content is very high (85%-150%, even more than 150%), which is in suspended state or flow state. This kind of foundation is currently mainly used in "two treatment techniques". Strengthening - that is, the shallow layer of shallow surface soil is pretreated with shallow surface rapid reinforcement technology (which belongs to vacuum preloading technology without sand cushion) for 30 days, while the hydraulic fill thickness is about 1.0m, the medium (powder) fine sand cushion and the mechanical paving (blow filling) thickness of 0.5m in the medium coarse sand drainage cushion, waiting for vacuum constant load After 45 days of unloading, the foundation can be used as the working platform for the construction equipment of the loading and drainage plate, and then the traditional vacuum preloading technology or vacuum combined loading preloading technology can be used to treat the deep soil soil. The main reasons for the two treatment of the newly dredged silt foundation are two aspects: (1) the newly dredged silt foundation The load is zero, can not directly bear any ground treatment construction machinery equipment (such as bulldozer, slotting machine, etc.); (2) the content of the clay particles (d < 0.005mm) in the newly dredged silt is high, the white heavy and silt is slow, the content of the strong hydrophilic mineral is high and the soil is absorbed by the combined water. The related performance indexes of the plastic drain board in the current regulation (including the drainage performance index) The engineering practice shows that in the process of rapid reinforcement of the shallow surface of the newly dredged silt foundation, the problem of silting in the vertical drain well is very serious, the efficiency of the drainage is dramatically reduced, and the soil strength between the vertical drains. It is very uneven, the soil strength growth is very limited, the effective reinforcement depth of the foundation is small, and the bearing capacity is low; the ground surface forms many "soil columns" centered on the vertical drainage wells, and the uneven settlement is very obvious. Therefore, the classical consolidation theory of sand well foundation and the existing method for calculating the strength of sand Ichi Ki strength are not completely applicable to this In this paper, firstly, the engineering characteristics of the newly dredged silt in different regions of the mainland of China are systematically summarized and analyzed. On the basis of practical engineering, the field contrast test of different forms of vacuum preloading drainage system is carried out. The negative pressure transfer characteristics and distribution patterns of this kind of foundation are discussed, and the corresponding vacuum is established. Then, according to the drainage consolidation characteristics of this kind of foundation, the calculation formula of soil strength growth is derived, and its rationality is verified through practical engineering. Finally, in view of the two real reasons of the above two treatment, the experimental research is carried out pertinent, and a new type of large area sand bed cushion process is developed. The new technology and new technology of dredging silt foundation provide new ideas for the successful implementation of one-time drainage consolidation treatment for newly dredged silt foundation. The conclusions of this paper are as follows: (1) the newly dredged silt in different regions of China is the product of the dredged silt at the stage of dynamic water deposition and hydrostatic deposition. In the vicinity of the outlet and the area far away from the outlet, the fine particles and fine particles are composed mainly of isolated pores and intergranular pores, and the microstructure characteristics are mainly turbulent and granular inlay structure. The content of d0.005mm and the strong hydrophilic mineral (illite, Mongolia) in the newly dredged silt. The content of the destone is high, the water content is greater than 90%, and the liquid limit is greater than 1.5 times, the pore ratio is more than 2, the plastic index is more than 20, and the engineering characteristic of the liquid index is basically greater than 2.0., which directly causes the newly filled silt foundation to be reinforced by the traditional vacuum preloading technology (including the shallow surface rapid reinforcement technology). There is a great difference between the consolidation deformation characteristics and the general soft foundation. On the macroscopic view, the serious "bending" phenomenon appears in the vertical drainage body and the serious "soil column" phenomenon of the movement of the fine soil particles to the vertical drainage body. (2) the traditional vacuum preloading technology (including the rapid reinforcement technique of shallow surface layer) is adopted. In the process of reinforcement, the loss of negative pressure in the whole drainage system is serious, the most serious is up to 57%, and the loss degree of the negative pressure from the shaft to the surrounding soil is very serious, at least 67%., which is the main reason for the limited increase of soil strength after the vacuum preloading of the newly dredged silt foundation. In the process of vacuum preloading of silt foundation, the negative pressure at the drainage boundary is nonuniform, and the negative pressure in the horizontal drainage cushion can be considered as a linear attenuation model with time change, while the negative pressure in the vertical drainage body can be considered as a nonlinear attenuation model with time variation. The theory of vacuum consolidation is given and the analytical solution is given accordingly. (3) based on the effective stress principle and the stress path method, the strength growth mechanism of the newly drained consolidation of the newly dredged silt foundation is qualitatively analyzed. The analysis results show that the strength growth law of the soil above the groundwater level line and the strength of the soil below the groundwater level line are increased. The long law is not the same. Based on the theory of effective stress uniqueness, the formula for calculating the strength growth of the drainage consolidation of new dredged silt foundation is derived. The formula comprehensively considers the vacuum load and its attenuation along the depth direction, the influence of the external load, the groundwater level and other factors, and relies on the actual engineering to calculate the formula. It is verified that the average error is 8% when considering the undrained shear strength, and the average error is 3.2% when the strength is considered on the failure surface. Therefore, the calculation precision can meet the engineering requirements. (4) the new large area sand cover work cushion is a large spatial stereoscopic structure, which is a water permeable structure, including the flat structure and lateral composite. The flexible structure and columnar structure (no need to set up in the mud foundation). The structure is integrated with the bottom floating (flow) mud foundation and has a high bearing capacity system. It can be used as the working platform of the deep drainage plate construction equipment. The bearing mechanism of this kind of cushion Foundation is mainly embodied in the shell like effect (including stress). Diffusion effect and surface closure effect, lateral closure effect (i.e. side limit), drainage consolidation and vertical reinforcement effect (no action in flow mud foundation). The failure form of this kind of cushion subgrade is characterized by punching shear failure. Scheme 7 (scheme 7 /) (woven geotextile specification is 280g/m2) is the best scheme. Based on the derived bearing capacity estimation The formula carries out the calculation, we know that the plastic load of the 7/ cushion foundation is Pcr=146.4kPa. this kind of cushion foundation service process, it is necessary to do well the cleaning measures and drainage measures in the construction process of the plugged plate. (5) the related performance indexes of the plastic drain board in the current standard (including the drainage energy index and the material strength index) and the high clay content new blowing. The inherent engineering characteristics of filling mud are not suitable, and the current vacuum preloading design is too fast to use the vacuum load loading rate to lead to the premature formation of the "soil column" phenomenon. These two aspects jointly lead to "the rapid reinforcement of the shallow surface layer of the newly dredged silt foundation, the strength of the soil is limited, the effective reinforcement depth is small, and the bearing capacity is still retained." It is impossible to meet the demand for construction land. The experimental results show that the vertical drainage body consisting of a medium equivalent pore (such as O95 0.15mm) and a strong bent core can be used as a vertical drainage system, and the vacuum preloading is strengthened with a faster vacuum load loading rate. The purpose of one-off drainage consolidation treatment is now.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU447;TU472

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