摘要
稳定和变形问题是在软土地基上建造建筑物遇到的两大主要问题,而软土的强度是软土地基稳定的决定性因素。软土随着排水固结强度不断增长是软土的重要工程特性之一,这种强度的增长对于低承载力的软土地基而言十分重要。掌握软土地基的强度增长规律是合理控制软土地基上路堤填筑速率、缩短工期、获得更科学、更经济的路堤填筑方法的基础。本文结合湖南省交通科技攻关项目,依托湖南省高速公路软土地基原位测试、软土强度参数室内外试验、理论推导和分析等方法对山间洼地软土地基强度特性、强度增长计算方法和工程应用进行了些探索,主要研究工作和成果如下:
(1)比较系统地对山间洼地软土地基进行了三种原位测试强度对比试验,建立了十字板抗剪强度Cu与轻便动力触N10的回归公式,为试验地区的山间洼地软土原位测试强度分析奠定了基础。
(2)对山间洼地软土进行了大量系统的物理力学指标试验,用统计回归的方法建立了山间洼地软土物理力学指标、室内试验强度指标与原位试验强度指标之间的回归方程。在试验数据的基础上,进行了软土强度指标的灰色关联度计算,分析了各物理力学指标对软土强度影响的敏感性。试验成果为掌握山间洼地软土的工程特性提供参考。
(3)进行了软土的固结和直剪试验,研究了不同固结压力作用下,抗剪强度指标c、φ随固结度(时间因素)的变化规律,以及一次性加载与逐级稳定加载对抗剪强度增长规律的影响,并建立了软土抗剪强度室内试验参数c、φ与固结度的拟合方程,其对软土路基的安全填筑具有指导意义。
(4)充分考虑公路地基承载力特点(柔性“基础”、荷载分布为梯形、强度因固结增长),通过理论推导,获得了中低填土高度路堤下软土地基承载力增长计算理论公式,为计算路堤下软土地基承载力及其增长、推算各阶段路堤填筑安全高度提供了一种有效方法。
(5)应用本文提出的软土地基承载力计算公式,计算了具有不同初始抗剪强度参数粘聚力和内摩擦角的软土地基在不同的固结度下的地基承载力值。基于计算结果,编制了软土抗剪强度参数随固结度增长的实用化表格,便于设计时使用。
(6)考虑软土地基强度随时间(固结度)的增长,将路基稳定性分析和沉降计算有机结合起来,较好地克服了以往路基稳定性分析和沉降计算“隔离”分析的缺点,提出了基于强度增长理论的,能综合考虑稳定性和工后沉降的路基动态施工控制计算方法,并编制了计算机应用程序。
Stability and deformation are two major problems in constructing buildings on soft ground. And Soft soil strength is a decisive factor in stabilizing soft ground. Soft soil strength increasing with the drainage consolidation is one of the important engineering characteristics. It is very important for soft ground of the low bearing capacity to increasing strength. To Master growing rule of strength is the foundation of reasonable controlling embankment filling velocity on soft soil, shortening the construction period and getting more scientific and more economical embankment filling method. Combined with communications science and technology project in Hunan and basis of researches at home and abroad, a number of exploration on the growth mechanism of soft ground strength, calculation method and engineering applications have been carried out relying on in-situ test of soft ground of expressway in Hunan, indoor and outdoor tests on soft soil strength parameters and theoretical analysis. The research results are as follows:
(1) Systematically carried out three kinds of in-situ test on strength of soft soil foundation between mountains in Hunan. Regression equation of the cross plate shear strength (Cu) and light sounding test blow count (N10) was established. Those test research fruit laid the foundation for soft soil strength analysis of in-situ tests in test area.
(2) Large amounts of physical and mechanics parameters test were carried out. Regression equation of parameters individuals and laboratory test index and in-sute test index based on test data. Factors influencing the bearing capacity of soft soil foundation is studied by means of grey relational analysis. Test fruit can heip to master the engineering characteristic of soft soil between mountains.
(3) The consolidation tests and direct shear tests of soft soil were performed. The law of shear strength index of soft soil change with its degree of consolidation under different consolidation was studied. The affection of loading method, namely, one time loading and the stepped loading on thelaw of shear strengthwas researched. The relationships between degree consolidation and index of shear strength were recommended. The result can be referenced to the fill construction of embankment on soft soil.
(4) Fully considering bearing capacity characteristics of the basement (flexible foundation, trapezoidal load distribution and strength increase due to consolidation), through theoretical derivation, calculation theoretical formulas of bearing capacity of low fill soft soil foundation was achieved. A new method was presented for assessing the bearing capacity under embankment at construction stage.
(5)The formula is applied to calculate the increments of bearing capacity of soft soil foundation.Baesd on calculation results,a bearing capacity increasing calculation table was put forwads,which enhance the application value of the formula.
(6) Considering soft soil foundation strength increasing with time (consolidation) and combining the stability analysis with settlement calculation organically to overcome the previous shortcomings; based on growth theory of strength, the research propose a dynamic control computing method of construction of embankment considering the stability and post-construction settlement and prepare the computer application program as well.
引文
[1]邓学锋,刘松玉.扰动对软土强度影响规律研究[J].岩石力学与工程学报,2007,26(9):1940-1945
[2]顾长存,刘胜松.公路软土地基原位强度特性探讨.岩土工程界,2005,8(8):67-70
[3]Gibson, R.E.,Experimental determination of the true cohension and the true angle of internal friction in clays.Proc.3rd ICSMFE,Vol,1953
[4]林孔锱.预压地基的强度增长与稳定问题[J].岩士工程学报,1998,20(1):93-96.
[5]孔德金,孙万禾.粘士抗剪强度内摩擦角统计分析,2000,313(2):10-13
[6]杨红军,熊磊.长江三角洲软土原位测试结果相关性分析.土工基础,2010,24(1):79-82
[7]李承海,张德波.广州南沙软土十字板剪切强度与比贯入阻力的对比试验分析[J].人民珠江,2004(2):8-12
[8]吴占寿,刘惊玲.深圳湾近岸软土静力触探与十字板剪切试验成果相关分析[J].岩土工程技术,1998(3):15-18
[9]孟高头.土体工程看擦原位测试及其工程应用[M].北京:地质出版社,1992
[10](DGJ08-37-2002、J10206-2002)上海市建设规范,岩土工程勘察规范[S]
[11]魏汝龙.固结不排水三轴试验结果的整理与分析[J].地基处理,2000,11(3):31-33
[12]颜庆智,付长波,饶江,杨凤军.东营软土工程特性及参数相关方程[J].中国石油大学学报(自然科学版),2010,34(3):130-134
[13]Leroueil S,Tavenas F.Mieussens C.Construction pore pressures in clay foundations under embankments,Part Ⅱ:generalized behavior[J].Canadian Geotechnical Journal,1978,15(1):66—82.
[14]Skempton, A.W. Residual Strength of Clays in Landslides,Folded Strata and the Laboratory[J]. Geotechnique,1985,35(1):3-18
[15]高大钊.软上地基承载力的确定方法[J].同济大学学报(自然科学版),1995,23(3):259-264
[16]Henkel D J.The Relationship Between the Strength,Pore Water Pressure and Volum-Change Characteristics of Saturated Clays,Geotechnique,1959(9):119-135
[17]Hvorslev M J.Physical Components of Shear Strenth of Saturated Days.Proc.of Res.Conf on Shear Strength of Cohensive Soil ASCE,1960
[18]Rendulic L.Relation Between Void Ratio and Effective Principal Stresses for a Remoulded Silty Clay.Proc.1st ICSMFE.
[19]Sridharan A, Nagaraj H B. Compressibility Behavior of Remolded, Fine grained Soils and Correlation with Index Properties. Canadian Geotechnical Jr. 2000,37(3):21~33
[20]胡世华,王侠民.上海地区粘性土有效内摩擦角与塑性指数关系.大坝测试与土工测试,1997,21(2):8-9
[21]折学森.软土地基沉降计算.北京:人民交通出版社,1999,21-25
[22]徐晓泉.昆明地区地基土指标与静力触探指标相关关系分析.云南大学学报(自然科学版),2000,22:103-105
[23]Fim Spink, Geotechnical Software Review. The Electronic Journal of Geotechnical Engineering,1996,(1):45~48
[24]Arai, K., Ohta, H. and Kojima. K.. Estimation of soil parameters based on monitored movement of subsoil under consolidation. Soils and Foundations[J], 1984,24(4),95~108
[25]Gioda, G and Jurina, L., Numerical identification of soil structure interaction pressures[J].Int. J. for Numerical Anal. Methods in Geomechanics,1981,(5)33~56
[26]E.W.Brand L.R. P. Brenner. Soft clay engineering[M].Elserier Scientific Publishing Company, Amsterdam,.1981
[27]Henkd D. J (1960)The shear Strength of saturated remoulded clays.Research Conf.on shear Strength of Cohensive Soil p.535. ASCE
[28]Skempton A W.The bearing capacity of clay.In:Building Research Congress eds.Selected Papers on Soil Mechanics,London:Thomas Telford Limited,1984
[29]Bjerrum,L.,Geotechnical problems involved in foundation of structures in the North Sea.Geotechnique,23(3):319-324
[30]Ladd C C.Stability evaluation during staged construction. Proc ASCE, J GED, 1991,117(GT4):540-615
[31]LARSSON R.Undrained shear strength in stability calculation of embankments and foundations on soft clays[J].Canadian Geotechnical Journal,1980,17(4):591~ 602.
[32]包伟力,周小文.地基强度随固结度增长规律的试验研究[J].长江科学院学报,2001,18(4):29-33
[33]Tika, T.E., Vaughan, P.R.,Lemos, L.J.L.J. Fast shearing of pre-existing shear zones in soil[J]. Geotechnique,1996,46(2):197~233.
[34]Hemmat, A. Relationship between pre-compaction stress and shear strength under confined and semi-confined loadings for a sandy loam soil[J]. Biosystems Engineering,2009,102(2):219-226
[35]Ali, Faisal Hajil, Osman, Normaniza. Shear strength of a soil containing vegetation roots[J]. Soils and Foundations,2008,48(4):587~596.
[36]Braja M Das. Advanced soil mechanics. Hemisphere PublishingCoporation,1983
[37]左佐生(译).路堤下地基土承载力的提高[J].铁道建筑,1995,(6):31-35
[38]沈水龙,余恕国,蔡丰锡.分级施工河堤下高灵敏性黏土的强度增加[J].岩土力学,2006,27(9):1519-1523
[39]徐书平,刘祖德,鲍华,袁子厚.堆载预压过程中的地基稳定性计算方法[J].岩土力学,2005,26(6):955-959
[40]Maaitah, Omer Nawaf. Experimental verification of a theoretical model for the shear strength of unsaturated soil[J]. Electronic Journal of Geotechnical Engineering,2005,(10):125-134.
[41]Ltifi, Mounir. Experimental study of ageing effect on the undrained shear strength of silty soil. Proceedings of the 4th International Conference on Soft Soil Engineering-Soft Soil Engineering,2005,(10):125~134.
[42]Ulusay, R.,Tuncay, E., Hasancebi, N. Geo-engineering properties and settlement of peaty soils at an industrial site (Turkey) [J]. Bulletin of Engineering Geology and the Environment,2010,69(3):397~410.
[43]张银屏,宫全美,软土抗剪强度随固结度变化的试验研究[J].岩土工程界,2004,8(2):37-40
[44]唐炫,魏丽敏,胡海军.不同固结度下软土的力学特性[J].铁道勘察,2009,(4):16-17
[45]Kumruzzaman, Md., Yin, Jian-Hua. Influences of principal stress direction and intermediate principal stress on the stress-strain-strength behaviour of completely decomposed granite[J]. Canadian Geotechnical Journal,2010,47(2):164~179.
[46]Ye Guan-bao, Guo Yong-fa. Tests and analyses on shear strength increment of soft soil under Embankment fill[J]. Electronic Journal of Geotechnical Engineering,2010.15A:1-9
[47]Hossain Md.Akhtarl,Yin Jian-Hua. Behavior of a compacted completely decomposed granite soil from suction controlled direct shear tests[J]. Journal of Geotechnical and Geoenvironmental Engineering,2010.136(1):189-198
[48]龚晓南.高等土力学[M].浙江大学出版社,2003
[49]董华炜,邓伟文.土体K0固结-卸荷剪切试验研究[J].工程勘察,2008,(5):13-16
[50]Gibson,R.E.,G.L.England and M.J.L.Hussey.the theory of one dimensional consolidation of saturated clays[J].Geotechnique,1967,17(3):261-275
[51]Bishop,A.W. A.K.G..Eldin.the effect of stress history on the relation between Φ and prosity in sand.3rd ICSMFE,1953,(1):100-108
[52]Dvis,E.H.,G..P.Raymond,A non-linear theory of consolidation[J].Geotechnique, 1965,15(2):161-170
[53]Nakase A, Kamei T,Kusakable O.Constitutive parameters estimated by plasticity index.Jr.of Geotech.Eng.,ASCE,1988,114(7):52-63
[54]OHTA H,NISHIHARA A.Anisotropy of undrained shear strength of clays under axi-symmetric loading conditions[J].Soils and Foundations,1985,25(2):78-86.
[55]ZDRAVKOVIC L,POTTS D M,HIGHT D M.The effect of strength anisotropy on the behaviour of embankments ground[J].Geotechnique,2002,52(6):447-457.
[56]王立忠,叶盛华,沈恺伦,胡亚元.K0固结软土不排水抗剪强度[J].岩土工程学报,2006,28(8):970-978
[57]Tsuchida T, Kobayashi M, Mizukami J.Effect of ageing of marine clay and its duplication by high temperature consolidation[J].Soil and Foundation,1991, 31(4):133-147.
[58]曾国熙.地基处理手册[M].北京:中国建筑工业出版社,2000
[59]沈珠江.软土工程特性和软土地基设计.岩土工程学报,1998,20(1):100-111
[60]Terzaghi K,Peck R B.Soil mechanics in engineering practice.2nd ed.New York:John Wiley&Sons Inc.1967
[61]Casagrande A, Wilson S.Effect of rate loading on the strength of clays shales at constant water congten, Geotechnique,1951.2(3)
[62]中华人民共和国行业标准,港工工程技术规范(JTJ79-2002)[S].北京:中国建筑工业出版社,2002
[63]中华人民共和国行业标准,建筑地基处理技术规范(JTJ79-2002)[S].北京:中国建筑工业出版社,2002
[64]魏汝龙,张凌.稳定分析中强度指标问题[J].岩土工程学报,1993,15(3):20-24.
[65]孔德金,苗中海.软粘土抗剪强度增长规律,1999,21(6):757-759
[66]Brink,R.G.,Triaxial compressient and extension tests on remoulded clay[J]. Conf.,Oslo,1967,1(1):13-20
[67]Gibson,R.E.,K.Knight and P.W.Taylor.A critical experiment to examine theories of three-dimensional consolidation.Proc.Europ.Conf.SMFE,1963,(1):71-80
[68]秦植海.饱和粘性土任意固结度的不排水剪强度指标的推求方法[J].工程勘察,1996(5):19-21.
[69]杨嵘昌.饱和粘性土任意固结度的不排水剪强度[J].南京建筑工程学院学报,2001(4):20-24.
[70]魏丽敏.软土路基双重非线性流-固耦合仿真分析与沉降预测[D].博士学位论文,中南大学,2005.
[71]胡亚元,陈云敏.本构模型与软黏土强度增长的关系研究[J].浙江大学学报(工学版),2004,38(6):731-736.
[72]徐书平,刘祖德.比奥固结理论在堆载预压加固工程场地中运用[J].岩土力学,2003,24(2):307-311.
[73]王军.结构性软土地基的固结沉降及稳定研究[D].博士学位论文,浙江大学,2002.
[74]郑晓国,刘松玉,经绯.软上地基路堤临界高度确定方法探讨[J].公路交通科技,2005,22(10)35-40
[75]张诚厚,袁文明,戴济群.软粘上的结构性及其对路基沉降的影响[J].岩土工程学报,1995,17(5)25-32
[76]王晓谋.河滩相软土地基变形规律及硬壳层作用规律[D].长安大学博士学位论文,2001
[77]姜荣泽,黄鉴麟.上海高速公路软土地基处理技术杂谈[J].公路工程,1998,11(2)12-16
[78]张迎春,李根祥.从广珠高速公路软基试验工程谈软基处理经验与问题[J].水运工程,1999(5):12-18
[79]Leroueil.Embankments on soft clays[M].New York:Ellis Horwood Limited,1990, 150~179.
[80]VAUGHAN P R.Assumption,prediction and reality in geotechnical engineering[J].Geotechnique,1994,44(4):573—609.
[81]秦建平,陈栓发.软基路堤现场观测结果的分析与工程应用[J].西安公路交通大学学报,1997,17(1):5-8
[82]Leroueil S,Tavenas F.Mieussens C. Construction pore pressures in clay foundations under embankments,Part Ⅱ:generalized behavior [J].Canadian Geotechnical Journal 1978,15(1):66—82.
[83]A.W.Bishop, The Use of Slip-circle in the Stability Analysis of Slops[J].Geotechnique,1995,5(1)
[84]Spencer E.,A Method of analysis of the stability of embankment assuming parallel inter-slice forces[J].Geotechnique,1965,15(1):78-84
[85]Morgenstern N.R. and Price, V.E., The analysis of the stability of General Slip Surfaces[J].Geotechnique,1965,15(1):89-95
[86]Sama,S.K.,Stability Analysis of Embankments and Slopes[J], Geotechnique, 1993,23 (3):47-52
[87]Whitman R.V,Bailey W.A.,Use of computers for slope stability analysis[J].Geotechnique,1960,10(4):70-77
[88]Janbu N.,Slope Stability Computations.Embankment-Dam Engineering,1973
[89]R.A.Zienkiewizo.A Limit Eguilibuium Design Method for Reinforced Embankments on Soft Foundations,2nd, International conf.Of Gestexiles,1976
[90]Barron R.A. Consolidation for fine-grained soils by drain wells, Trans ASCE 1984.113
[91]Rowe, R.K. Reinforced Embankments on Soft Cohesive Deposits. Report in China 1992
[92]Ycuceman M S,et al. Three-dimentional stability analysis of slopes, Structure Safety,1990,19(1)
[93]A-GrivasJ.Geotech.D, Asaoka A. Slop safety prediction under static and seismic loads.Div. ASCE,1982,108(GTS)
[94]肖武权,冷伍明.软土地基承载力指标灰色关联分析[J].勘察科学技术,2005,(2):3-115.
[95]柳雁玲,佴磊,江娟.软基处理路堤极限填高计算分析[J].公路,2005,(11):115-120.
[96]钱家欢殷宗泽.土工原理与计算[M].北京:中国水利水电出版社,2002.
[97]孙钧.地下工程设计理论与实践[M].上海:上海科技技术出版社,1996.
[98]K.太沙基著,徐志英译.理论土力学[M].北京:地质出版社,1960
[99]Hansen J.B.,A general formola for bearing capacity[J].The Danish Geotechnical Institute Bulletin,1961 (11):105-115
[100]Fellenius, B.H. From strain measurements to load in an instrumented pile[J].The Danish Geotechnical Institute Bulletin,1961(11):105-115
[101]邓永锋,刘松玉,洪振舜.高速公路工程中动态临界填筑高度的应用研究[J].岩土力学,2006,27(9):150—179.
[102]王宗生,张海涛.软上泥沼地区公路路堤临界高度的确定[J].东北公路,1994,(1):23-26
[103]FATabenas, C Chapeau, La Rochelle, MROY·Immediate Settlement of Three Test Embankment on Champlain Clay [J]·Canadian Geotechnical Engineering 1974, J11:109-139
[104]MS S Almeida, M C R Davest, RHG Parry·Centrifuge Tests of Embankments on Strengthened and Unstrengthened Clay Foundations [J].Soils and Foundations,1986,26 (4):19-36·
[105]颜可珍,王晓谋,夏唐代.河滩相软土地基路堤沉降变形分析[J].岩土力学,2004,25(7):1099-1103
[106]陈小平,白世伟.软土蠕变-固结特性及计算模型研究[J].岩石力学与工程学报,2003,22(5):728-734.
[107]Brand E W, Brenner R P.Soft Clay Engineering[M].Amsterdam:Elserier Scientific Publishing Company,1981.
[108]Fredlund D.G..,Krahu J.Comparision for slope stability methods of analysis[J].Canadian Geotechnical,1977,104(3):50-55
[109]陈仲颐,周学星,王洪瑾.土力学[M].北京:清华大学出版社
[110]Skempton A W.The bearing capacity of clay.In:Building Rearch Congress eds.Selected Papers on soil Machamcs, London:Thomas Telford Limited,1984
[111]Hansen J B.A revised and extended formula for brearing capacity.Danish Geotechnical Institute Bulletin,1970(28):5-11
[112]陈敏华.软基上路堤稳定性能量分析方法.[硕士学位论文].北京:铁道科学研究院,2007.
[113]S Leroueil, F Tavenas. B TrakP, La Rocheile, M Roy·Construction Pore Pressures in Clay Foundations Under Embankments PartⅠ:theSaint-Alban test fills [J].Canadian Geotechnical Engineering,1978 J15:54-65·
[114]何群,冷伍明,魏丽敏.软土抗剪强度与固结度关系的试验研究[J].铁道科学与工程学报,2005,2(2):51-55
[115]刘开富,谢新宇,张继发,朱向荣.软土地基上路堤填筑的破坏性状分析[J].岩士力学,2009,30(7):2075-2081
[116]陈涛,郭院成,谢春庆.平坦地基上山区高填方路堤变形及稳定性分析[J].郑州大学学报(工学版),2009,30(3):39-43
[117]黄世武,刘明维,尹健.膨胀土地基路基填方失稳破坏模式分析[J].重庆交通大学学报(自然科学版),2009,28(2):250-254
[118]中华人民共和国国家标准,《公路桥涵地基与基础设计规范》 JTJ 024-85
[119]白冰等.软土工程若干理论与应用[M],中国水利水电出版社,2002
[120]高有潮.三角形及梯形荷载下地基中塑性区的开展规律与地基临界荷载的确定[A].中国土木工程学会第一届士力学及基础工程学术会议论文集[C],1964年8月
[121]张启岳.堤基塑性变性区的计算方法及许可荷载的确定[A].软土地基学术讨论会论文集[C].北京:水利出版社,1980
[122]铁道部基建总局技术处.在软土地区修筑路基的经验[J].土木工程学报,1959(10)
[123]冷伍明,赵健,何群.路堤下软土地基承载力的计算研究[J].土木工程学报,2005,38(4):120-124
[124]饶波,魏丽敏.一种填筑软土路基的稳定性控制方法[J].公路交通科技,2005,22(2):46-49