Evaluation of pile bearing capacity from results of static penetration tests using a probabilistic approach

Conclusions 1. Based on a probabilistic approach taking into account the natural heterogeneity of the soils in the engineering-geologic elements and the depths at which they are located, the analytical value of the pile bearing capacity was obtained (for the specified probability of unfailing operation) from the static penetration test results.2. The analysis of the factual material indicates a possible increase, by 16–25% (for R=0.95) in comparison with the SNiP II-17-77 Norms (since January 1, 1987 with the SNiP 2.02.03-85 Norms) of particular values of the limit resistance of the pile at the penetration point.Soyuzgiprovodkhoz. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 7–9, July–August, 1987.     

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.     

Effect of boring method on bearing capacity of short cast-in-place piles

Conclusions 1. Bored-hole/cast-in-place piles 4–10 m long tend to retain a constant value of the unit bearing capacity, irrespective of soil moisture. Driven piles, and piles cast in punched holes, undergo a loss unit bearing capacity (up to 20%) as their length is increased.2. With the saturation of high-porosity collapsible soils, the unit bearing capacity of bored-hole/cast-in-situ piles up to 10 m long diminishes two to three times, on average. For cast-in-place piles installed in a punched hole, and for driven piles, this reduction ranges up to only 30%. This trend is characteristic of soil layers whose collapsibility properties diminish with depth, from 2–3% to 1–1.5%.3. The unit bearing capacity of cast-in-place piles installed in punched holes is equal to that of driven piles, both for saturated and dry soil conditions.4. Following soil compaction, the unit bearing capacity of concrete cast-in-place piles installed in punched holes is higher than for bored-hole/cast-in-place piles, in the ratio of up to 2 for slightly moistened soils and 3–3.5 for saturated soils.5. All other conditions being equal, the unit bearing capacity is greater for driven piles, and somewhat smaller (by 10–15%) for piles cast in punched holes. The smallest unit bearing capacity is observed in bored-hole/cast-in-place piles (1.5–2 times less than for driven piles).Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 14–15, July–August, 1979.     

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.     

Optimal design of foundations of short piles with a monolithic grillage for rural construction

Conclusions 1. For the more effective use of short piles it is necessary to continue investigations and to supplement Tables 1, 2, and 6 of SNiP II-B.5-67* with consideration of the possibility of using piles with a depth less than 3 m.2. It is necessary to revise the instructions in point 9.4 [2] with respect to the minimum distance between piles 3d and to allow reducing it in cases when this is justified by the incomplete use of the bearing capacity of the piles and economic considerations.Petropavlovsk Rural Construction Administration. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 21–24, September–October, 1975.     

Design of beds and foundations for rural buildings framed with three-hinge mill bents

Conclusions 1. Until more modern methods of computation are developed, it is recommended that the bearing capacity of beds for rigid rectangular foundations of agricultural buildings framed from three-hinge mill bents with a relative embedment 0.5h/B1 and angles of incline of the resultant of external loads 20<<45° from the vertical be determined by the method outlined in ICR 0.1–76. The method described in SNiP II-15-74 should be used when the relative embedment of the lower surface is less than 0.5 and the angles <.2. It is recommended that the long side of rectangular foundations be placed in the direction of the shearing force.3. As has also been noted by other investigators, determination of the effective width of a foundation in accordance with the Gersevanov method leads to excessive safety factors in estimating the bearing capacity of a foundation bed. The need has arisen to develop more accurate procedures that take into account the configuration of the lower surface of the foundation, the relative embedment of the lower surface, and other factors.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 6, pp. 14–16, November–December, 1982.     

Ways to increase the economical effectiveness of foundations for agricultural buildings with three-hinged bents

Conclusions 1. The failure of a sandy foundation bed under a rigid embedded reinforced-concrete foundation (h/b0.5) with a flat, rough lower surface is three-dimensional in nature when the loads are inclined at =20–40° to the vertical.2. Plane shear is not observed when the load is inclined at an angle = and the eccentricity e0 ( is the angle of the soil's internal friction as determined on a shear apparatus in accordance with GOST 12248–66).3. The settlements and lateral displacements of an embedded foundation (h/b>0.5) in the limiting state are 2–3 times larger than those of the nonembedded foundation; lateral displacements exceed the limiting values established for farm buildings [2], or approach them.4. For angles =20–40°, eccentricity of the inclined load in the direction opposite to the horizontal component, but not less than r_C (r_C is the core radius of the section) effects an increase in the ultimate load as compared to a central positioning of the resultant. Additional experiments and theoretical studies are required to investigate the role of positive and negative eccentricity on the bearing capacity of the foundation bed.5. For loads inclined at angles =35–40° and a relative foundation embedment 0.5h/b1, computation in accordance with SNiP II-15-74 yields considerably lower bearing capacity than computation from experimental data.6. The studies that we conducted are used to develop a more economical method of computing and designing foundations for farm buildings under an inclined loading, which is employed in practice [2].B. E. Vedeneev All-Union Scientific-Research Institute of Hydraulic Engineering. Central Scientific-Research Institute of Experimental Design and Planning for Rural Construction. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 3–6, July–August, 1979.     

Computing the settlements of foundations placed on beds with layers of weak clayey soils

Conclusions 1. In designing natural foundation beds with layers of weak clayey soils, the final settlements of the foundations and the settlements with time can be computed using the theories of elasticity and seepage consolidation in accordance with the method outlined in the paper. This is confirmed when additional (over and above the natural) pressure p₀ 5c are applied to the top of the weak clays, where c is the minimum specific cohesion of the clayey soils as determined with allowance for the possible reduction in cohesion with time. When p₀ > 5c, including pressures on the roof of the weak clays equal to the design pressures given in Section 3.62 of SNiP II-15-74, there are only isolated cases of building construction from which it is impossible to judge laws governing bed deformation.2. In conformity with Section 1, the method of computation clarifies the computation of settlements as compared with SNiP II-15-74, simplifying the design of beds with layers of weak clayey soils.Scientific-Research Institute of Bases and Underground Structures (NIIosnovanii). Estonian Institute of Industrial Design and Planning. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 15–18, July–August, 1981.     

Strength Characteristics of Frozen Saline Soils

Methods for determination of the strength characteristics of frozen saline soils (FSS) are examined. The shear parameters C _lt and _lt for typical soils of the Yamal Peninsula are determined over a broad range of negative temperatures (from – sign;1 to – sign;8°C) and salinities (from 0 to 1.5%). Proposed tabular data on strength characteristics of FSS make it possible to use them in calculations to determine limiting loads on bed soils.     

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.     

Design values of strength characteristics of frozen saline soils

Based on a large number of personal tests and analysis of results of investigations of other authors, the writers comment upon the design values recommended in the SNiP 2.02.04-88 Norms for the strength characteristics of frozen saline soils.NIIOSP Institute. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 27–29, March–April, 1993     

Resistance of frozen soils to disintegration under high-pressure hydraulic jets

Conclusions 1. The frozen soil volume disintegrated by a high-pressure hydraulic jet is proportional to its initial specific kinetic energy.2. As the water content of frozen soils increases, and also as their temperature decreases, the depth of the slit cut in them by the hydraulic jet decreases also.3. The relations between the depth of cut in frozen clays and their temperature are practically similar to the curves of content of non-freezing water in these soils in the temperature interval from –1°C to –5°C.Scientific-Research Institute of Bases and Underground Structures. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 21–23, May–June, 1984.     

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.     

Discussion of SNiP 2.02.04-88 Norm "bases and foundations on permafrost soils"

From the Editors: The complexity of construction on permafrost soils, as well as numerous cases of deformation of structures constructed on such soils, calls for an especially careful design and construction approach. The preparation of all editions of the SNiP Norms for design of bases and foundations on permafrost soils (including the last edition 2.02.04-88 of the SNiP Norms), has always been carried out with the participation of many different organizations, and their discussion is of a wide nature. However, after edition of the latest SNiP Norms and their approbation in the engineering practice, continuation of this discussion is highly desirable.For this reason, on publishing the present article without any evaluation of the recommendations contained in it, the Editors ask the specialists in the field of foundation construction on permafrost soils to express their opinions about the questions considered in the article as well as about other criteria of the SNiP 2.02.04-88 Norms.Vorkuta Branch of the "Komigrazhdanproekt" Institute. PechorNIIproekt Institute. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 30–32, March–April, 1993.     

Experimental investigation of behavior of pile clusters in permafrost soils

Conclusions 1. The cluster effect depends on the state of the frozen soil; for hard-frozen soil it is manifested for a distance L2d between the piles, and for a plastic-frozen soil, for L 4d.2. For plastic-frozen soils account must be taken of the nonlinear creep settlement of the pile cluster, which is larger than the settlement of a single pile. The relation among the settlement, the number of piles in the cluster, and the distance between the piles has been established, and the corresponding method of analysis has been proposed.3. The load on the piles in the cluster is nonuniformly distributed, depending on the cap rigidity, the number of piles, the distance between them, and the state of the frozen soil. As a rule, the most loaded piles are those located farthest from the cap center, and the least loaded are those located inside the cluster.4. By applying the method of analysis of rigid plates on elastic bases of M. I. Gorbunov-Posadov, it is possible to analytically determine the loads on the piles in the cluster.Moscow Civil-Engineering Institute (MISI). Zabaikalpromstroniiproekt YaNIF Institute. Translated from Osnovaniya, Fundamenty i Mekhanika, Gruntov, No. 2, pp. 8–11, March–April, 1988.     

Stabilization of settlement of base and correction of tilt of a 16-story residential building on pile foundations

Conclusions 1. For insufficient bearing capacity of the pile group and development of significant settlement, a grating was added which substantially improved the bearing capacity of the piles and reduced the settlement of the pile field.2. Modern methods of evaluating the bearing capacity of piles by carrying out static tests made it possible to achieve effective solutions, since the safety factor was low (the removal from service of only two piles from the group of about 30 piles immediately led to development of additional settlement).3. During the carrying out of pile construction work, special attention should be given to the recording, in the pile-driving logbook, of the number of blows of the hammer, the height of fall, and the refusals, since these data may reveal piles with low bearing capacities.4. For construction of tall buildings on weak soils having complex stratification, even on piles, it is necessary to perform observations on the development of settlements during construction and operation.Lenniiproekt. Leningrad Civil Engineering Institute. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 9–11, July–August, 1981.     

Introduction of rectangular pyramidal piles in Belorussia

Conclusions 1. The investigations corroborate the results of well-known theoretical and practical studies on the effect of the geometric shape of piles on their bearing capacity. A computational analysis and model and full-scale pile tests established some quantitative relationships between the bearing capacity and shape of driven piles currently being used in construction.2. Investigations and construction experience indicate that there is no "universal" pile which is optimal for all structures and all types of soil conditions. According to the results of investigations of short driven piles, and from design and construction experience, it can be concluded that for loose and medium-density, homogeneous sands and clay soils having a consistency ranging from semistiff to soft/plastic, it is expedient to adopt rectangular pyramidal piles for large-scale construction in the conditions in Belorussia, instead of the prismatic type, as they have shown that, under the above conditions, the volume of pile work is reduced 1.6 times, and labor consumption and costs are reduced commensurately.Belorussian Polytechnical Institute (BPI). All-Union State Trust of Enterprises for Manufacture of Construction Machinery (Stroimekhanizatsiya). Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 8–10, January–February, 1980.     

Bearing capacity of driven piles in sandy soils according to resistance characteristics and their variability

Refined standard resistances are suggested for sandy soils under a point and along the side surface of piles, and also their reliability coefficients with different confidence levels established by statistical-probability processing of full-scale static tests. The suggested procedure not only makes it possible to raise the transmitted load on piles, but to efficiently use their bearing capacity with consideration of the degree of responsibility of the buildings and structures being designed.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 14–17, September–October, 1992.     

Performance of vertically loaded combined pile foundations

Conclusions 1. Bending moments, which increase in proportion to the settlement and the angle of incline of the piles, develop in inclined piles as the CPF settle under load. The possibility of their determination in accordance with the method outlined in [4] has been substantiated experimentally.2. Proceeding from conditions of the optimal performance of inclined piles and conditions under which their strength is ensured, it is established that it is expedient to adopt an angle of incline within the range of 5–6° for the piles.3. A method of calculating the bearing capacity of CPF from static-penetrometer data, proceeding from the hypothesis of the possibility of determining the strength of CPF as the sum of the strengths of its component elements with allowance for strength assurance in the material of the inclined piles, is proposed. The discrepancy between computed and experimental data was 16–32% as a factor of safety.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 6, pp. 15–18, November–December, 1991.     

Investigation of the bearing capacity of beds of foundations with an inclined base

Conclusions 1. Experiments showed that the total influence of the coefficients taking into account the inclination of the load in conformity with SNiP II-15-74 substantially underestimates the bearing capacity of beds. Correction of the values of these coefficients is possible, provided the accumulation of considerable experimental data.2. The bed bearing capacity does not depend on the sign of eccentricity in the plane of one of the axes of the foundation.3. For large inclinations of the load it is expedient to change to foundations with an inclined base, which permits increasing the bed bearing capacity as much as 40%.Scientific-Research Institute of Bases and Underground Structures (NII Osnovanii). Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 27–29, January–February, 1980.