【正文】 復合土層的壓縮模量，一般可按下式估算： （4） 式中——為水泥土樁樁身的壓縮模量，可?。?00～120），本工程取600Mpa；——為天然地基土的壓縮模量，參考勘察報告來確定；——為復合土層的壓縮模量；——面積置換率，； 按地基土分層計算如下：對于粘土層，Es= Mpa，代入（4）式計算得Esp= Mpa；對于下部土層，經加權平均求得Es= Mpa，代入（4）式計算得Esp= Mpa； 下臥層沉降量S2的估算根據公式 （4）式中——下臥層頂面處的附加應力，Kpa，計算得=；——為第I層土的壓縮模量，Kpa，參考勘察報告來確定；——沉降計算經驗稀疏，根據地區(qū)沉降觀測資料及經驗確定；、——為下臥層至第i層和第i－1層底面的距離，m；、——為下臥層計算點至第i層和第i－1層底面范圍內的平均附加應力系數；本工程下臥層壓縮層厚度=（－）=16m式中為基礎寬度。將數據代入式（4），滿足規(guī)范要求。墊層，～，它可以使基礎壓力經墊層擴散吼較均勻的作用于復合地基。，是為了改善基礎與復合地基的接觸條件，以利于樁間土發(fā)揮承載作用。經一系列方案對比與設計計算，最終本工程設計為：夯實水泥土樁復合地基，樁徑400mm，%，水泥摻入比為10%， Kpa，滿足工程要求。試驗采用剛性壓板置于試樁中心點上，通過分級加載，觀察分析其所加荷載與沉降變形的關系，繪出P—S曲線?？梢钥闯觯瑥秃系鼗o載荷試驗曲線基本屬于漸進型的光滑曲線，不存在陡降點。取s/b=（b為方形壓板的寬度）對應的荷載，其值均超過最大加荷量的一半，因此取最大加荷量的一半作為夯實水泥土樁的單樁復合地基承載力設計值。即水泥土樁復合地基承載力值大于300Kpa，復合地基承載力提高2倍，滿足設計要求。為對比加固前后樁間土承載力的變化，完工后，布置了3個輕便觸探點進行是試驗。綜合分析樁間土測試結果知，經水泥土樁處理后樁間土的承載力基本值不低于120Kpa，比地基處理前的樁間土承載力有所提高。本工程低應變檢測水泥土樁樁身完整性415根樁，檢測比例為30%均屬基本完整性樁。4 結論與體會（1）以復合地基靜壓結果數據看，本工程所采用的水泥土樁可最大限度地發(fā)揮該種樁的優(yōu)點，使復合地基的承載力得到大幅度的提高，地基變形得以降低和控制。(2)復合地基中由于夯實水泥土樁樁體材料僅為水泥，不配筋，充分發(fā)揮樁間土的承載力，其受力和變形類似于素混凝土樁，具有地基承載力高、變形小、穩(wěn)定快、施工簡單易行、工程質量易保證等優(yōu)點，工程造價一般還比CFG樁便宜，經濟效益和社會效益非常顯著。（3）夯實水泥土樁處理地基是一種效果明顯的處理方法，用夯實水泥土樁加固后的復合地基比原地基變形模量會有很大增長，抗變形能力有明顯提高。（4）是否設置褥墊層以及墊層的材料和厚度，直接影響復合地基的樁和樁間土強度的發(fā)揮，合理的墊層厚度對提高復合地基承載力和減少沉降變形是非常有利的。（5）由該工程證明此種地基處理方案，質量易控制、造價低、經濟、社會環(huán)境效益明顯，有極大的發(fā)揮潛力。參考文獻：[1]徐至均，：機械工業(yè)出版社，[2]閻明禮， 8專業(yè)外文翻譯Influence of humic acid and salt concentrationon limestabilized ariake clays and microstructure researchAbstract: This study first investigates the effects of humic acid,and salt concentration on limestabilized Ariake clays with emphasis on their mechanical results show that the strength and yield stress of limestabilized clay with high humic acid are low due to the obstruction of the pozzolanic reaction,and the effect of humic acid on strength of stabilized clays decreases with increasing salt concentration because the humic acid because inactive at higher salt concentration . Then through analyzing the microstructure feature of the stabiliaed clays,some relationship between microstructure and mechanical properties of limestabilized clays are established.Introduction:Ariake clay is a highly sensitive soft clay deposited around the coast of the Ariake Bay in Kyushu Island , nature water content varies from 50 to 200%.Most of the Ariake clays are classified as CH,and the sensitivity exceeds to its very high water content and low shear strength ,improvement of Ariake clays with in a short period is popular improvement method is to use chemical additives such as major strengh gain of limestabilized clay mainly is derived from three reactions, . hydration , ion exchange and pozzolanic reactions, in which cementing products, such as CSH(CaO－SiO2－H2O) and CAH(CaO－Al2O3－H2O), are formed.Organic matter in the clay is responsible for high plasticity, high shrinkage, high pressibility, low hydraulic conductivity, and low shear strength. It is generally accepted that the presence of the organic matter in the clay may lead to the detriment of the strength of limestabilized clays. However, some studies have shown that not all of the organic pounds really have a negative effect on the cementing process.The study first attempts to prehend the effect of humic acid, a kind of organic matter, and salt concentration on limestabilized Ariake clays. The strength and the pressibility of the limestabilized clays were investigated by unconfined pression test and consolidation tests. These tests were conducted on clays with organic matter extracted and various amounts of humic acid mixed.As salt concentration is known to be one of the dominant factors in the strength of the limestabilized clays, this study also investigated the influence of the humic acid.The observation on microstructure of soil is useful to appreciate the relationship between soil structure and its mechanical behavior. In the case of limestabilized clay, the study on the microstructure yields more information than that of nature clay owing to that the microstructure of stabilized clay is a bination of cementation bond and fabric. In the present research, the microstructure feature of the stabilized clays was observed by Atterberg limit, permeability tests, Scanning Electron Microscope(SEM) and Mercury Intrusion Porosimetre(MIP). We try to relate the mechanical results of limestabilized clay to these microstructure test results of account for the relationship between them. At last, two schematic diagrams of influence of humic acid and salt concentration on limestabilized Ariake clay will be presented.Experiment method:The Ariaka clay samples used here were obtained from (a)Okawa,area, Fukuoka Prefecture, (b)Ashikari area, Saga Prefecture, and (c)Isahaya Bay, Nagasaki prefecture, designated as Clay 1,Clay 2,and Clay 3,respectively(see table1).Quick lime was applied for the stabilization. The clays were mixed with 5,10,and 20% lime by mass of dry soil. In order to eliminate the effect of the differernces in water content, distilled water was added to Clay 2 and Clay 3 to adjust the water content to 185% that is the natural water content of Clay addition of distilled water in both clays had little effect on their salt concentrations.Table 1 Properties of Ariake claysProperties Clay 1 Clay 2 Clay 3Water content/% Liquid limet/% Plasticity index/% Specific gravity/() Sand/% 3 3 0Silt/% 29 37 19Clay/% 68 60 81 PH Salt concentration (Dichromate absorption)