Stresses and displacements in the soil under a circular foundation

Conclusions 1. For the first time, the methods of the theory of elasticity and the theory of limiting equilibrium have been used for establishing the curvilinear nature of the relations S=f(P), which corresponds to the nature of this relation observed in tests with trial loads.2. For all cases of embedment of the plate and for loads substantially smaller than the limiting loads, the contact pressure diagrams are similar to those obtained by the theory of elasticity, but do not exhibit any special characteristics under the edges. This agrees with the results of experimental investigations carried out in order to determine the contact pressures.3. The plate displacements, for all other conditions being equal, and also for loads exceeding 0.3 MPa, depend substantially on the relative embedment of the plate in the soil or on the soil cohesion.4. For practical analyses, the relation S=f(P) obtained by solution of the elastoplastic problem can be approximated by a hyperbola.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 38–40, September–October, 1974.     

Investigation of the effect of a vertical surcharge on horizontal displacements and resistance of pile columns to horizontal loads

Conclusions 1. The principle of independence of the action of forces in the general case is not applicable to calculation of pile columns with relative embedment < 15. A vertical surcharge can somewhat decrease (in weak saturated soils) or increase (in clays of very stiff consistency) the resistance of pile columns to horizontal loads. In the investigated saturated soils, the bearing capacity decreased by no more than 15%, and in very stiff slump-prone soils it increased by a factor of 1.9.2. Under equal conditions, pile columns with cantilevers absorb a 1.3–1.6 times greater horizontal load than prismatic.3. When designing pile columns, the depth of their conditional embedment in the soil should be determined in conformity with the requirements of Instructions [12] and not by Table 12 in SNiP II-B.5-67*, since this leads to uneconomical reinforcement of the pile columns.4. For pile columns of agricultural buildings a permissible crack width of 0.3 mm should be adopted instead of the 0.2 mm according to SNiP II-B.5-67*.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 11–14, January–February, 1978.     

Technicoeconomic basis for selection of pile and pile-foundation designs

Conclusions 1. In addition to the factors enumerated at the outset of this paper, the character of the given external effects should be considered in selecting a pile design.It is expedient to use large-diameter (60–120 cm) predrilled-and-rammed piles in cases where the piles should sustain large (100 kN and greater) horizontal loadings, and driven or predrilled-and-rammed piles with a pedestal where the piles should sustain large vertical loads.2. The advantage of one pile design over another should be weighed from both the cost indicators, and the material-outlay indicators for the pile and pile-foundation design, taking into account the resources of the construction organizations as a basis for a variant design.State Institute for the Design and Planning of Beds and Foundations. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 13–16, January–February, 1976.     

Reliability index for offshore piles subjected to bending

A first order second moment formulation is developed for analyzing the reliability of individual cross sections of piles driven on soft soils and subjected to random lateral static loads. The soil properties are expressed in terms of random p–y curves for a set of non-linear Winkler springs. The stiffness of the pile is taken as deterministic, but uncertainty about bending strength is accounted for. An algorithm is proposed and applied for determining probabilistic second moment estimates of internal forces and lateral displacements of a pile, taking into account both non-linear behavior and uncertainty about the parameters of the p–y curves. The cases studied include hypothetical piles driven on identical soft clays, and the loads correspond to the design conditions representative of several locations throughout the world. Very wide variations are found for the reliability index β of piles designed in accordance with ordinarily accepted regulations.     

The question of assigning a bed coefficient in calculating rigid airport pavements

It is suggested that the bed coefficient be considered as a characteristic of the contact interaction of rigid pavement and the soil base. Equations are derived for the relationship between the bed coefficient and the modulus of elasticity of the soil base for reinforced-concrete and metal pavements. They are compared with the results of experimental investigations, indicating sufficiently good correspondence of these values. Patterns of operation of pyramidal piles in swelling soils are given: the dependence of their rise on the cone angle, length of the pile, and transmitted load. The authors studied layer-by-layer displacements of soil around a pile and give their dependences on the depth of the layer's location. Formulas are given for determining the coordinate of the neutral point, according to which the rise of an unloaded pile is found.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 16–18, July–August, 1993.     

Experimental investigations of the reactive strength of soil in the bed of a circular footing subjected to short-term dynamic loads

Conclusions 1. The distribution of contact stresses along the foundation slab of a rigid circular footing in a sandy soil subjected to dynamic loads in a steady-motion regime is saddle-shaped in nature and agrees with corresponding literature data derived from static tests. In this case, an increase in contact stresses from 0.2–0.5 to 1.0–1.5 MPa at the center of the plate will effect a reduction of from 1.60–1.80 to 1.30–1.50 in the concentration factor; this is associated with the enhancement of the role played by plastic deformations in the bed.2. The reactive strength of the soil in the bed of a circular rigid footing subjected to short-term dynamic load can be represented in the form of Eq. (1). In this case, the computed velocity a₁ should be determined with allowance for the actual ₁() curve, which corresponds to the work of the soil beneath the plate under conditions of a certain deformation regime.3. Use of the hypothesis that we have cited will make it possible to predict with an accuracy sufficient for practical calculations the maximum loads on foundation slabs placed on the surface of the ground for structures, and the parameters of their motion under blast-induced loads of rather high intensity.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 10–12, May–June, 1990.     

Investigation of the bearing capacity of piles driven in plastic frozen soil

Conclusions The bearing capacity of a pile lowered into a borehole whose cross section exceeds the cross section of the pile for the possibility of filling in with slurry (frozen-in, friction, bored-sunk piles) is close to the calculated, but has a greater settlement under a standard load in comparison with a bored-drive pile.The bearing capacity of piles driven by the VMS-1 vibratory hammer into plastic frozen soil (bored-drive piles) is on the average 1.6 times greater than the calculated. Such an excess of the bearing capacity of the piles can be explained by the formation of a new structure and frost texture of the soil within 30–50 mm around the pile skin. A characteristic feature of the newly formed zone of soil is a considerably greater homogeneity and density of the soil than under natural conditions and absence of ice lenses and interlayers directly contacting the pile.The settlements of the pile tested under a standard load were less than the allowable deformations for the bases of the majority of buildings and structures.The cross-sectional area of the pilot hole should be equal to 0.65–0.75 of the pile section in the case of driving it at the time of the maximum depth of thawing of the soil and 0.95 at the time of seasonal freezing of the soil.Restoration of the contact bonds between the soil and pile during its freezing-in after driving into soil with a temperature of -0.5°C and higher can continue for several months.Deceased.Central Scientific-Research Institute of Transport Construction (TsNIIS). Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 19–20, January–February, 1979.     

Effect of lateral earth pressure on the limit load and settlement of the sand base of a plate

The results of a model experiment on loading the sand base of a plate with preassignment of various lateral earth pressures are examined. An increase of lateral earth pressure reduces the limit load on the base and under loads exceeding the initial critical load causes an increase of settlement of the plate. The reliability of the result obtained in the experiment is proved by a numerical analysis of the limit stress state at a point.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 8–10, May–June, 1992.     

Settling of large buildings and structures erected on clay loess grounds

Conclusions 1. Some 60% of foundation settling in clay grounds of the type considerered here takes place during the construction period. The settling continues for 10 years, and then for an additional 20–25 yr at a very low rate.2. The II-B.5–67 scheme of pile foundation, proposed by the SNiP from the analysis of deformations, is substantiated by the actual settlings.3. Settlings calculated by different methods differ but little among themselves and are in fair agreement with the actual settlings. The single instance of great discrepancy between the theoretical and actual data evidently is due to changes in ground facies and the rate of compactions.4. The published data [1, 2] on a marked discrepancy between the theoretical and actual data on settleling for the large structures should be regarded as anomalies associated with foundations in sandy grounds and acted upon either only by the static loads (minor settlings) or by the combined static and dynamic ones (large subsidences).5. Observations of settling should start with the construction, at loads not exceeding the operational, with accurate records kept on loads transmitted to the foundation.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 29–31, September–October, 1971.     

Finite element analysis of tunnel–soil–pile interaction using displacement controlled model

Significant additional loads could be induced in pile foundations adjacent to new tunnels. Accurate prediction of magnitude and shape of the ground displacements, which define curvature changes, is crucial for the computation of tunnelling induced bending and axial stresses in pile foundations. The finite element simulation of tunnelling by removing forces corresponding to initial stress-state, tend to predict incorrect shape of ground displacement profiles, hence incorrect forces in pile foundations adjacent to tunnels. To overcome this difficulty, this paper describes the development and application of a simple and useful displacement controlled model (DCM) to predict the effects of tunnel excavation on adjacent pile foundations. The DCM simulates tunnelling by applying displacements to the tunnel boundary. A method to determine magnitude and direction of tunnel boundary displacements, based on convergence patterns observed in field and centrifuge test results, is proposed. Back analyses of numerous greenfield tunnel case histories using the DCM indicate good agreement between computed displacement profiles and field/test data. The suitability of the DCM in modelling tunnel–soil–pile interaction problems is demonstrated through back analysis of a centrifuge test and a field case study.     

Actual and calculated loads on piles and results of observing settlements of a large-panel building

Conclusions 1. During the construction period the loads on extreme piles along the axes of transverse bearing walls are considerably greater than on the middle ones.2. Under the effect of rigidity of the building a redistribution of the loads on the piles during its operation occurs even in the absence of a grillage, i.e., the more loaded piles are unloaded and the less loaded ones are additionally loaded.3. The actual loads on the piles in the operating period are considerably less than the calculated, which indicates the need to refine the recommendations of SNiP II-6-74 for the purpose of taking into account the useful loads in calculating the foundations of residential buildings.4. The factor =0.2, concerning conversion from settlements of single piles in static tests to settlements of piles in foundations under long-term load, given in the draft of the new edition of SNiP II-17-77, is acceptable.5. To accumulate data on the actual loads on pile foundations it is necessary to continue their measurements under various soil conditions.Deceased.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 17–19, May–June, 1977.     

Design of beds for pyramidal piles in accordance with a second group of limiting states under combined vertical, lateral, and moment-induced loads

The three-dimensional contact problem for a pyramidal pile under combined vertical, lateral, and moment-induced loads is solved by the method of boundary elements. A linearly deformable half space weakened by a cavity, the geometric dimensions of which are identical to the contact surface of the pile, is used as a soil model. The resultant solution is compared with familiar theoretical results and experimental data. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 5–9, July–August, 1997.     

Multifunctional combined foundations on permafrost soils

The writers examine the construction of multifunctional combined foundations on permafrost soils, as approved for strengthening the foundation system of an administrative-industrial building in Norilsk. Such foundations make it possible to control the building deformations developed as a result of increase in the pile loads or in the settlements of the piles due to decrease in their bearing capacity when the soil base temperature increases.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 26–28, September–October, 1992.     

局部承载黏土地层浅埋隧道稳定机制的连续上界极限分析

针对局部承载黏土地层浅埋隧道施工的横断面稳定机制问题,采用上界极限分析理论和基于Peck公式及不排水不可压缩条件的地层位移模式,分别计算研究了地层物理力学参数、浅基础荷载参数、桩基础荷载参数对隧道必要支护压力下确界的影响。在其他参数不变的前提下,隧道必要支护力下确界随地层抗剪强度的增大而线性地减小,随地层重度的增大而线性地增大;随浅基础荷载量值的增大而线性地增大,随浅基础荷载横向距离的增大而非线性地减小并趋于定值,随浅基础荷载横向范围的增大而非线性地增大并趋于定值;随桩基础侧面剪力荷载量值、底面压力荷载量值的增大而线性地增大,随桩基础荷载横向距离的增大而非线性地减小并趋于定值;对端承桩而言,当桩基长度小于（或大于）地层沉降竖向分布曲线极大值点对应的深度时,随桩基长度的增大而非线性地增大（或减小）。     

Performance characteristics of horizontally loaded piles located near a trench

Conclusions 1. The excavation of a trench (pit) in the vicinity of a pile diminishes its ability to resist horizontal loading. This reduces the depth of pile embedment in the soil and depends on the depth of the trench and its distance from the pile.2. The above-described method of testing piles for horizontal loading with strain gages can be used to determine the design depth of pile embedment in a soil.3. The upper layer of soil of thickness d exerts no significant influence on the performance of horizontally loaded piles due to the formation of a gap between the pile and soil during its backfilling and can therefore be disregarded in their disign.Scientific-Research Institute of Industrial Buildings and Structures. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 13–14, May–June, 1976.     

Construction of pile foundations for instrudial farm buildings

Conclusions 1. For industrial farm buildings of column-beam construction with full frame the most promising foundations are pile-posts of the forced-sinking and the bored types, and for industrial buildings with partial frame, residences, and cultural buildings of up to three stories the following types of foundations offer advantages: short, drilled-bored soil-concrete or cyclopean concrete 0.5–0.8 m in diameter; driven tapered footings 1.5-2-m-long; and prestressed piles without transverse reinforcement.2. It is necessary to develop methods for calculating driven and bored piles with lengths of 1.5–3 m as well as pile-posts working under the combined effect of vertical and horizontal loads, since the lack of such methods hinders the further introduction of pile foundations in farm construction.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 12–15, July–August, 1968.     

Piles injected into predrilled holes in soils prone to slump-tyre settlement

Conclusions 1. Drill-and-inject piles of increased bearing capacity with a diameter of 250–400 mm and more and a depth of up to 50 m and more, which are embedded into underlying soils not prone to slump-type settlement can be used in loess soils classed as type-II in terms of proneness to slump-type settlement.2. The use of washing mud based on sodium silicate, which eliminates slump-type settlement of the soils during pile fabrication and reduces the friction against their lateral or surface by 10–15% within the limits of the stratum prone to slump-type settlement, lowering the negative loads on the pile, is effective when piles are injected into predrilled holes in soils prone to slump-type settlement.3. Drill-and-inject piles 250–400 mm in diameter and up to 50 m long have a design bearing capacity of from 0.50 to 2.50 MN and can be recommended for the installation of new, and the strengthening of existing foundations for civil and industrial projects in soils prone to slump-type settlement.4. A special set of equipment, which makes it possible to ensure the continuous production of work that includes the drilling of holes, assembly of reinforcing cages, and the filling of the holes with a hardening grout, should be used for the installation of these piles."Soyuzgidrospetsstroi." Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 18–20, January–February, 1988.     

Development of foundations of small-section piles and their introduction to construction

Conclusions 1. The use of small-section piles for the foundations of lightweight buildings and structures significantly reduces material consumption and labor outlays for their construction.2. The technology and embedment equipment, as well as designs of small piles and pile foundations from these designs, which have been developed as a result of experimental construction, will make it possible to introduce these piles on a broader scale in construction practice.3. The basic positions of Construction Norm and Regulation II-17-77 with the refinements proposed in this paper can be used to compute the bearing capacity of small-section piles subject to vertical and horizontal loads and for dynamic tests.Deceased.Scientific-Research Institute of Industrial Buildings and Structures. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 6–8, January–February, 1981.     

Effect of pore water pressure on tunnel support during static and seismic loading

The support of underground structures must be designed to withstand static overburden loads as well as seismic loads. New analytical solutions for a deep tunnel in a saturated poroelastic ground have been obtained for static and seismic loading. The static solution accounts for drainage and no-drainage conditions at the ground–liner interface. Linear elasticity of the liner and ground, and plane strain conditions at any cross-section of the tunnel are assumed. For tunnels in which ground stresses and pore pressures are applied far from the tunnel center, the drainage conditions at the ground–liner interface do not affect the stresses in the liner. The analytical solution shows that the stresses in the liner are exactly the same whether there is drainage or not at the ground–liner interface. Hence, if the drainage conditions in the tunnel are changed from full drainage to no-drainage or vice versa the stresses in the liner are not affected. However, the stresses and displacements in the ground change significantly from drainage to no-drainage conditions. For seismic loading a new analytical formulation is presented which provides the complete solution for the ground and the liner system for both dry and saturated ground conditions. The formulation is based on quasi-static seismic loading and elastic ground response; for a saturated ground, undrained conditions are assumed which indicate that the excess pore pressures generated during the seismic event do not dissipate. The results show that the racking deformations of a liner in dry or saturated ground are highly dependent on the flexibility of the liner.     

Tests of driven piles in slump-prone soils under the effect of horizontal and elastic loads

Conclusions 1. Flooding of a soil base leads to a substantial increase in deflection of piles under the effect of horizontal loads.2. Fixing the piles at the level of their head leads to a decrease of deflection and increase of their bearing capacity.3. An increase of reinforcement compared to series 1.011-6 has little effect on deflection of piles at the first stages of loading, but has a considerable effect on their ultimate bearing capacity.4. For horizontal loads of 15 kN per pile its deflections in flooded soils of type I slump-proneness do not exceed 10 mm, which is permissible for the given type of buildings.Trust for the Organization of Construction Technology, Main Administration for Construction in North Caucasian Regions (Orgtekhstroi Glavsevkavstroya). Kharkov Design and Scientific-Research Institute of Industrial Construction (Promstroiniiproekt). Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 14–15, May–June, 1980.