And these are verified by load test in site to validate the conclusion that the testing result on four piles area is closed to the result with the group piles effect in large area composite foundation and to determine the bearing capacity of composite foundation of single row piles and double rows piles , the result from single pile composite foundation is acceptable 得到确定大面积复合地基承载力的荷载试验中，一般测试4根桩所处理的面积，测得的承载力就能较好地接近在群桩效应下的结果，而确定单排或双排群桩复合地基的承载力，单桩或双桩复合地基荷载试验的结果便行。
This paper adopts the large diameter cast - in - situ piles of the north pier of anqing changjiang highway bridge as the study backgrounds , uses the pile calculative program , gpile that is a part of the common program software system of finite element method , sap84 , to calculate and analysis the pile group effect of large diameter cast - in - situ piles deeply with different coefficients of pile group effect 本文以安庆长江公路大桥北塔墩大直径钻孔灌注群桩基础为研究背景，应用有限单元法通用程序软件系统sap84中的gpile桩基计算程序对不同群桩效应系数下大直径钻孔灌注桩的群桩效应进行较深入的计算和分析。
When the frequency approaches zero , the factor approaches zero correspondingly ; 2 ) the amplitude of interaction factors changes with the incident angle of rayleigh waves and reaches maximum when is zero . moreover , with the increase of , the wave period shortens apparently ; ( 3 ) the amplitude of interaction factors decreases as the pile spacing increases and approaches to zero when the pile spacing is 15 ; 4 ) the amplitudes of interaction factors increase clearly with the increasing stiffness ratio of pile to soil ; 5 ) the lat eral seismic response of fixed - head pile groups is much smaller than that of free - head pile groups . moreover , the pile - group effects induced by rayleigh waves can be neglected ; 6 ) the lateral seismic response of piles at different location differs from each other 得到了以下结论： 1 )桩的相互作用因子随频率呈周期性变化，在振动频率比较低的情况下，桩的横向相互作用因子也较低，当频率趋近于零时，相互作用因子也趋近于零； 2 )桩的相互作用因子的幅值随瑞利波入射角度的变化而变化，在= 0情况下幅值最大，且随入射角度的增加，波动的周期明显缩短； 3 )桩的相互作用因子的幅值随着桩与桩间距的增加而减小，至s d = 15时，桩的相互作用因子基本趋近于0 ； 4 )在频率比较低时，相互作用因子幅值随桩土相对刚度比的增加而显著增加； 5 )桩顶固接可以有效地降低群桩的横向地震响应幅值，由瑞利波产生的群桩效应可以忽略不计； 6 )群桩中不同桩位的桩的横向地震响应是不同的，每根桩所在的桩位对其横向地震响应有很大的影响；刀桩数的增加并不能减小桩的横向动力响应。
At present , there are many research methods on pile groups subjected to lateral loads at home and abroad . however , it is still far from meeting the demands of pile groups appliances in engineering . using the finite element software ansys , the article calculates and analyses the behavior capacity of pile groups first 本文首先运用目前国内外应用较为广泛的有限元软件ansys对群桩基础进行有限元分析：分析了横向荷载作用下群桩的桩距、桩数、桩径、桩长、土体模量等因素对群桩效应的影响，得出了一些有益的结论。
This thesis put forward a systemic method to settle the negative friction in project design . it includes when the negative friction must be consider , the zero position decided , count the down load , the negative friction group pile , the infection on end - bearing and sedimentation and stability , how to deal with in design to avoid the negative friction and how to solve when the negative friction produced 本文提出了在工程设计中如何处理桩基负摩擦力的方法，包括什么情况下考虑负摩擦力、负摩擦力中性点位置的确定、桩基下拉荷载的计算、负摩擦力的群桩效应、负摩擦力对桩基竖向承载力和沉降的影响、设计施工中如何避免出现负摩擦力以及对已经出现的负摩擦力如何根治。
Correlative function method and variable function method are used to calculate the relevant range of soil layer . the limit capacity of bored pile is determined by the cone penetration tests ( cpt ) and the static loading tests and related statistics parameters are also evaluated . considering the effects of group piles , the action effect is calculated by the settlement of pile foundation and the reliability index of single pile as well as group piles is determined by monte - carlo method 本文选择临近场地的四座高层建筑地基的全部勘测资料，以沿深度方向的一维平稳高斯随机场作为桩基土层土性参数的数学模型，利用相关函数法和变异函数法计算土层的相关范围，由cpt和静载试验结果综合确定钻孔灌注桩的极限承载力，进而对相同场地各试桩的承载力进行折算后检验其概率分布，并估计有关统计参数：考虑群桩效应确定桩基承载力，由桩基沉降反算其作用效应，由monte - carlo方法计算单桩及群桩的可靠指标。
The thoughts that the ratio of the volume of pile and soil in the ambient range of pile group is used to express the reduced coefficient is put forward . the p - y curves of pile group after reduced are adopted as horizontal interaction model . on these conditions , pile group effect of large diameter cast - in - situ piles is analyzed nonlinearly 本文提出以群桩周边包络线范围内的桩身体积与土体体积(含桩体积)之比来描述这一折减系数，并采用此将单桩p - y曲线进行折减后得到的群桩p - y曲线作为桩土横向作用模型，对安庆长江公路大桥北塔墩大直径钻孔灌注桩的群桩效应进行非线性分析。
