Analysis of piles and pile grillages on heaving soils

The concept of interaction between a heaving soil and individual and group piles and pile grillages, which makes it possible to determine both the magnitude of layer-by-layer uplift of soil around an individual pile and within a group of piles, and the piles themselves, is discussed. Specific examples of solutions are cited with comparison of predicted and actual values. __________ Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 25–30, March–April, 2006.     

Experience gained with the sinking of piles near existing building under soil conditions in lands along the Middle Ob'

Experience gained with pile driving near existing buildings in a accordance with the author's procedure, which takes into account conditions of the spread of elastic waves that develop in the ground during the driving of piles, and which does not cause soil deformations in the foundations beds of existing buildings, is presented. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 13–15, January–February, 2000.     

Application of pile foundations with grillage in frost zone of heaving soils

Conclusions 1. The installation of piles and pile foundations leads to a reduction in the heaving of soil in the space around the pile, the smallest values of which are observed inside the pile group. 2. Frost heaving decreases and, consequently, the normal forces of frost heaving that act on the grillage diminish with decreasing distance between piles in the group. 3. During freezing, the layers of soil exhibit a complex mechanical trajectory. As the freezing zone approaches these layers, they are displaced downward, i.e., the process of compaction of the thawed soil occurs under the pressure induced by the frost heave, and upward displacement of the soil layers (heaving) is then observed after freezing. 4. As a result of the freeze-thaw cycle, the soil in the space around the pile is compacted under the frost-heave pressure. The proposed construction of precast-pile foundations with a grillage in the frost zone has demonstrated its own serviceability. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 6–8, March–April, 1991.     

Deformed scheme for design of piles injected into predrilled holes

A method is proposed for the calculation of piles injected into predrilled holes with allowance for their flexibility and possible initial curvature of the pile's axis. The stability of the pile is assessed in the soil mass. An example is cited for the calculation of foundation strengthening by inclined piles. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, Nos. 4–5, pp. 8–12, July–October, 1998.     

Experimental investigations of pile loads and foundation settlements in tall large-panel buildings

Conclusions 1. During the process of settlement of pile foundations with and without gratings in the nine-story large-panel frameless buildings with transverse and longitudinal bearing walls, the loads were redistributed and equalized, which was a consequence of interaction between the relatively rigid building box and the pliant base of the foundation. 2. Field investigations of the actual pile loads in the foundations of the nine-story large-panel buildings made it possible to establish that the design pile loads exceeded the actual values by 12–16%. 3. The nature of the distribution of the forces in the elements of the pile foundations of the large-panel frameless buildings indicates the need for taking into account the pliancy of the soil base of the pile foundation and its joint operation with the constructional components of the building box for determining the pile loads and for designing the gratings as well as the wall panels with gratingless support. 4. In the pile foundations of the nine-story frameless large-panel buildings with load-bearing, frequently transverse walls of the type of Series 1-464D, with and without gratings on compressible soils, the loads in piles with equal rigidities of the soil bases can be assumed to act as uniformly distributed, as an approximation, in engineering analyses. In the case of different rigidities of the soil bases of the piles, the load on each pile can be determined as a force proportional to the corresponding rigidity. 5. The actual settlement of the pile foundation of the large-panel building on alluvial soils was greater by a factor of 5–6, and for the building on the clay soils of the Ufa floor it was greater by a factor of 15 in comparison with the settlement of a single pile constructed on the basis of the same static test results, under the same soil conditions, and for the same loads. Hence, the coefficient ζ recommended in the SNiP II-17-77 for transfer from settlements of individual piles in static tests to settlements of piles in foundations under long-term loading should be differentiated according to the soil type and state. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 8–10, March–April, 1982.     

Effect of frost-heave forces of soils on the bearing capacity of pyramidal piles

Conclusions 1. Foundations formed from short pyramidal piles can be used in soils slightly prone to heaving without any restructions placed on bearing capacity, and should never be used in soils highly prone to heaving. 2. The installation of foundations formed from short pyramidal piles 3–4 m long in soils moderately prone to heaving with a heaving modulus m ≤ 7 is possible in principle. In this case, however, the load on the pile should be limited to the value determined by computation as a function of the frost depth of the soil and the assigned length of the pile in conformity with the method outlined in the paper. 3. Since the results obtained and the conclusions drawn apply to piles only of three of the most widely used type sizes, and their investigation was limited only to three experimental sites, questions raised in the paper will require further study. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 6, pp. 8–11, November–December, 1989.     

Interaction between a slide-prone soil and piles with consideration of the configuration of the retaining structure

A computational scheme is proposed for interaction between a slide-prone soil and the piles of single-and two-row retaining structures by the finite-element method. Relationships of the limiting creep pressures on piles situated in a single row and also analysis of the stress-strain state (SSS) of the slide-prone soil on interacting with the piles of two-row retaining structures are presented. A procedure is proposed for analysis of anti-slide pile structures with allowance for their configuration. __________ Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 8–12, March–April, 2007.     

Force distribution among slope-protection structure pile rows

Conclusions 1. For design of slope-protection retaining structures consisting of rows of piles whose lower ends are elastically embedded in a fixed soil mass while their upper ends are free, use can be made of the following distribution of the slide pressure (in fractions) among the pile rows (the first row is reckoned from the slide pressure transmission side): in a two-row structure: 1st row, 0.55; 2nd row, 0.45; in a three-row structure, 1st row, 0.5; 2nd, 0.3; 3rd, 0.2; and in a four-row structure, 1st row, 0.35; 2nd, 0.3; 3rd, 0.2; 4th, 0.15. 2. For design of slope-protection retaining pile structures with a cast-in-place reinforced concrete cap rigidly joined to the pile heads, uniform distribution of the slide pressure among the pile rows can be used. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 7–11, March–April, 1990.     

Interaction between pile rows and sliding soil

A rigidly plastic model is proposed for analysis of interaction between pile rows and soil flows. The limiting forces acting on the pile elements of anti-slide structures are determined from the field of slip lines calculated by the method of boundary elements. Results of calculations from a program developed for a personal computer made it possible to derive a relationship between the stresses developed when soil is forced between the piles and their spacing in the row. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 2–6, March–April, 1997.     

Engineering method of analyzing the tilting of eccentrically loaded pile groups

An engineering procedure is presented for analysis of the tilts of eccentrically loaded pile groups; this procedure accounts for the length of the piles and the spatial flexibility of the foundations. It is based on results of analysis and codification of a large volume of experimental research on the performance of eccentrically loaded pile foundations under various soil conditions. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 12–14, March–April, 2000.     

考虑固结群桩竖向应力相互作用的积分方程分析方法

采用Biot 固结方程,分别以等长和不等长两桩为分析对象,将受竖向荷载作用的桩土体系分解成半空间饱和扩展土和虚拟桩,基于竖向应变协调关系建立桩土相互作用的第二类Fredholm 积分方程,求解出不同固结状态时的桩身轴力分布。在等长两桩中,由于邻近桩的存在,桩身附加轴力主要分布于桩身20%～80%深度处,其影响程度随着桩间距的增加而减弱。进一步将等长两桩分析扩展至群桩研究中,分析表明：群桩效应引起了桩顶荷载的不均匀分布;土体固结对桩身内力分布也有一定的影响,固结后角桩承担的荷载有所下降。桩长不等时,长短桩之间的相互作用效应并不一致,表现为两桩桩顶承受相同荷载时长桩沿桩身附加轴力增加较短桩明显。最后,将不等长桩相互作用系数应用于群桩的优化分析中,在保证总桩长和桩基沉降基本相当的情况下,通过调整不同位置的桩长使得各桩受力趋于合理。     

Analysis of piles in rock

A review of research on the performance of piles in rock is presented. It is demonstrated that the bearing capacity of a pile is determined not only by the uniaxial compressive strength of the rock in its bed, but also by such factors as the ratio of the diameter of the pile to the depth of its embedment, the ratio of the compression modulus of the rock mass to the elastic modulus of the concrete pile, and the conditions at the contact between the lateral surface of the pile and rock, as well as procedural characteristics of the work performed in installing the piles. __________ Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 8–12, January–February, 2007.     

Prediction of soil vibrations during pile driving from penetration data

A method of predicting soil vibrations during pile driving and determining safe distances to existing buildings using static-penetration data is discussed. Experimental data on determination of expected elastic failures of piles and elastic vibrations of the soil in the immediate vicinty of the pile using the slip factor are cited. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 7–9, January–February, 1995.     

Interaction of cast-in-place piles with soil under type II collapsibility conditions

Conclusions 1. Under the given and similar hydrogeologic conditions, the settlements of piles fully cutting through the collapsible mass and sunk 2–12 m into the noncollapsible soils, when the pile bearing capacity under the external load is satisfied, are practically equal to the ground surface settlements in the pile site.2. For long-term soaking of the soils from the top, the low position of the depth at which soil compression starts under the action of the dead weight of the mass (it is in the range 14–16 m), and the development of compression deformations in the noncollapsible layers, which prevents detachment of the upper soil zone from the piles, are essential under the given conditions.3. For increase in the pile length from 24 to 31 m and support on denser soil layers (alluvial clays), the soil base resistance and the additional load caused by the soil mass action increase correspondingly, but the pile settlements remain practically unchanged.For substantial reduction of the possible absolute pile settlements with prolonged soaking of the soils under the given hydrogeologic conditions, the pile length should be increased by about 20 m. However, for establishment of the foundation dimensions it is extremely important to compare the allowable and possible differential settlements of adjacent foundations, which are comparatively small under the given conditions.Scientific-Research Institute of Bases and Underground Structures. TISI. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 14–17, March–April, 1986.     

桩网复合地基的模型试验加固效果对比研究

为了探究不同形式的桩网复合地基加固软土的效果,设计了3组复合地基进行室内模型试验.第1组为PVC管材加固软土地基,第2组为桩承式复合地基,第3组为PVC管材与砂桩复合地基.在模型箱钢板内侧壁涂上黄油,并覆以塑料薄膜来减小边界效应；在PVC管材和土工编织网(格栅)上粘贴应变片,来测试PVC桩体应力及加筋拉力；在桩间土、砂...     

Effect of a pile driven in a predrilled hole on the stress-strain state of plastically frozen soil

The stress-strain state of a frozen soil around a pile sunk in a predrilled hole is investigated. It is demonstrated that when piles are embedded in a frozen soil by the drill-and-drive (and, not to mention, by driving) method, the formation of an ring region of thawing with a radius to several tens of centimeters is possible around the pile. Analyses that make it possible to determine the linear dimensions of the region of thawing soil being formed are conducted. __________ Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 28–31, July–August, 2007.     

Engineering method of analyzing the bearing capacity of horizontally loaded pile groups

An engineering method is presented for analysis of the bearing capacity of a horizontally loaded pile group on the basis of the resistance of a single pile with a free head; the method accounts for the interaction between piles in the foundation, and the rigid fixity of their heads in an undeformable grillage. Results of the analysis performed in accordance with the developed procedure are compared with data derived from field tests of pile foundations. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 7–11, March–April, 2000.     

长螺旋搅喷桩在基坑帷幕工程中的试验与应用

基于长螺旋搅喷桩用于基坑帷幕工程的工程案例,证明护坡桩＋桩间水泥土桩是一种很好的基坑帷幕隔水形式,而长螺旋搅喷桩在实现桩间水泥土桩和确保其与护坡桩搭接质量方面要优于传统的旋喷桩和搅拌桩。在基坑施工过程中,改变护坡桩与长螺旋搅喷桩的施工顺序,能克服护坡桩施工过程中因塌孔、桩位和垂直度偏差给长螺旋搅喷桩施工带来的困难,既可保证帷幕隔水质量,又能取得较好的社会效益和经济效益。     

Mathematical modeling of the installation of pile foundations in a dense urban setting

Principles are proposed for the construction of constitutive relationships for the solution of problems of geomechanics under large deformations. Examples are cited for the numerical modeling of the installation of pile foundations in accordance with various procedures for soil conditions found in Saint Petersburg. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, Nos. 4–5, pp. 13–18, July–October, 1998.     

长短桩桩基础与其它类型基础的比较分析

采用三维弹塑性有限元方法对全短桩、全长桩、长短桩复合地基和长短桩桩基础进行了比较分析。筏板分析采用弹性薄板理论,土体采用莫尔-库仑弹性-理想塑性模型,桩体采用线弹性模型,桩土之间接触面采用非线性弹簧模拟。针对不同基础类型,从沉降性状和桩顶荷载大小以及长短桩的桩身轴力分布规律方面进行了比较分析。得出长短桩桩基础的平均沉降小于全短桩基础和长短桩复合地基,但仍大于全长桩基础。长短桩桩基础中长桩的中性点位置比长短桩复合地基的要深一些,受到的负摩阻力稍大些。长短桩桩基础中短桩作用发挥要比长短桩复合地基的短桩充分,而且其长桩的最大桩身轴力相比也小。