<\/em><\/p>\n\n\n\nThis proposal is intended for plot surfaces greater than 0.5 Ha. For smaller plots, a minimum of 3 piles is recommended for testing.<\/p>\n\n\n\n
The proposed expression is derived from the trend of the \u00abSurface-Number of posts tested\u00bb curve obtained from the point cloud of all considered campaigns.<\/p>\n\n\n\n
Figure 3 and Table 1 show the graphical and numerical results for the proposed equation. Although the graph in figure 3 is limited to a maximum area of 500 Ha, data of up to a maximum of 2.000 Ha has been used to adjust the trend curve (PFV Al-Dhafra, in Abu Dhabi).<\/p>\n\n\n\n
Factors such as greater or lesser lithological variability or fluctuation in thickness and\/or strength, make it necessary to increase or decrease the number of test points. These factors must be taken into account for the quantitative design of the static load test campaign, highlighting the importance of using the data provided by the prior geotechnical study to design the campaign.<\/p>\n\n\n\n
Emphasis must be placed on the quality of the tests execution. It is crucial to avoid falling into the routine of executing tests without analyzing the results in parallel, to avoid adjusting campaign decisions. The extensive surface area of the plots leads to many tests that must be executed. Having a smaller number of correctly executed tests is prioritized over a larger number of tests with doubtful quality and difficult interpretation<\/p>\n\n\n\n
<\/p>\n\n\n\n
Fig.3: Number of piles to be tested depending on the surface of the plant in Ha<\/p>\n\n\n\n
Finally, the performance of tests per day is very variable and depends on the test procedure in terms of loading steps, preparation of the pile (with pre-drilling or not), time necessary for displacement stabilization, etc.<\/p>\n\n\n\n4. METHODOLOGY<\/h4>\n\n\n\n Before carrying out a campaign of static load tests it is essential to determine whether the piles can be driven directly into the ground or if preliminary work (such as pre-drilling) is required to facilitate driving. Therefore, during the preliminary feasibility study phase, the geotechnical study will test the capacity of the ground to admit a foundation solution. This can be done by driving piles through continuous dynamic penetration tests, or a preliminary ramming campaign that can also obtain preliminary data about the ground behavior against axial and lateral forces.<\/p>\n\n\n\n
Subsequently, it is crucial to carry out the ramming and static load test campaign during the project phase using piles with a similar cross-section to those designed for the project. This helps determine the areas in which direct ramming is feasible, project the embedment length of the piles, determine the ultimate strength parameters of the ground, and estimate the displacement of the structures for the viable foundation solutions.<\/p>\n\n\n\n
While the fundamental objective of a feasibility study is to evaluate the most appropriate construction method and pre-size the embedment length from initial data, the project phase requires more detailed information to draft a test procedure. It is important to know the approximate order of magnitude of the factored reactions of the structure in the foundation (tensile, compression, lateral load and bending) in order to size an embedment length and check its validity for all possible reactions, considering both the ultimate limit state and the service limit states (e.g., allowable displacements). Generally, the loads are applied in load-unload steps until a maximum value is reached, emphasizing the static nature of the applied loads. Although load-unload cycles are performed, the loads are applied during a time period that allows stabilization displacement and must be considered static.<\/p>\n\n\n\n
For the dimensioning and verification of a foundation with isolated metallic piles,permanent, variable, and accidental loads are considered static and must be treated in the calculation according to current regulations, similar to other building structure foundations and civil works.Effects such as the loss of long-term strength due to dynamic loads are outside the scope of this type of test.<\/p>\n\n\n\n
In soils more sensitive to strength variation with moisture content, it is common to simulate saturation conditions around the pile by flooding.<\/p>\n\n\n\n
4.1 Testing equipment<\/h4>\n\n\n\n The necessary machinery and measuring equipment for these tests include:<\/p>\n\n\n\n
\nDriving equipment and percussion rotary drilling equipment, with an energy capacity to drill at least 800-1.000 J. It is desirable for the drilling equipment to be capable of drilling holes up to a maximum diameter of 150-200 mm in case of high ground hardness.<\/li>\n\n\n\n Digital dynamometer with a calibration certificate and minimum capacity to measure up to 50,0 kN in any direction .<\/li>\n\n\n\n Load cell with a calibration certificate and minimum capacity to measure up to 50,0 kN in the axial direction of the profile.<\/li>\n\n\n\n Digital or analog micrometer for displacement measurement with enough range to measure the maximum expected displacement and precision of 0,01 mm.<\/li>\n\n\n\n Auxiliary elements: slings, pile-loading fixing devices, hoists, etc.<\/li>\n<\/ul>\n\n\n\nPhoto 1: Equipment owned by ORBIS TERRARUM for driving piles and drilling in case pre-drilling was necessary<\/em><\/p>\n\n\n\nPhoto 2: Dynamometer for measuring load applied assembled for lateral load test.<\/em><\/p>\n\n\n\nPhoto 3: Digital micrometer installed for vertical tensile load test<\/em>The application of the load to the pile can be carried out either through the construction of a loading frame, or by employing heavy machinery as a reaction. The load can be applied with a level or chain hoist for axial tensile load tests and lateral load tests, or with a hydraulic jack for compression tests. When the loading steps are not small it is common to apply the load with the hydraulic system of the machinery (excavator, backhoe loader\u2026).<\/p>\n\n\n\n
It is recommended that the heavy machinery used as reaction in the tests weighs at least 2-3 times the value of the maximum load applied<\/p>\n\n\n\n
4.2 Testing method<\/h4>\n\n\n\n The method of conducting load tests on driven piles, including: the number of load steps, duration of load application, and timing of displacement measurements, allows us to obtain conclusions about the ultimate ground strength, and the foundation\u00b4s behavior based on the measured absolute and residual displacements.<\/p>\n\n\n\n
Extrapolating the load-displacement graph based on the results of other tests is not admissible for obtaining the critical load or ultimate load of the elastic phase. If the final load is not reached due to soil failure, the maximum load applied in the test must be adopted as the ultimate load.<\/p>\n\n\n\n
It is recommended to perform a test per driven pile, either a lateral load test or an axial load test, aiming to achieve the ultimate ground strength, the maximum load of the load device, or the maximum load allowable by the pile before depleting its resistant capacity.<\/p>\n\n\n\n
However, the most common practice is to use the driven pile to carry out the two tests1<\/sup>. This practice is considered acceptable, with the recommendation that the lateral load test be performed first. Once it is verified that the pile has not sustained considerable deformations and is suitable for a second test, the vertical load test can be conducted. This guideline, while not a general rule,may also depend on the value of the reactions in the foundation or the pile-ground behavior in the first tests. It follows the recommendations indicated in Eurocode 7, particularly in sections 7.5.2, \u201cStatic load tests\u201d and 7.7.2, \u201cResistance to lateral loads obtained from pile load tests\u201d which states:<\/p>\n\n\n\n7.5.2.1 (4) Pile load tests for the purpose of designing a tensile pile foundation should be carried out to failure. Extrapolation of the load-displacement graph for tension tests should not be used.<\/em><\/p>\n\n\n\n7.7.2 (2) Contrary to the load test procedure described in 7.5, tests on transversely loaded piles need not normally be continued to a state of failure. The magnitude and line of action of the test load should simulate the design loading of the pile.<\/em><\/p>\n\n\n\n4.2.1 Pile tests<\/h4>\n\n\n\n During the pile driving, the driving time by segments must be registered. This is necessary to determine the driving speed and estimate ramming production. Additionally, it will provide qualitative data that together with other test results from the geotechnical study, will help to more precisely delineate areas with different behaviors in terms of ground strength.<\/p>\n\n\n\n
The figure below shows an isoline map of pile driving times for a static load campaign carried out in Egypt.<\/p>\n\n\n\nFig. 4: Example of driving time isoline map<\/em><\/p>\n\n\n\n4.2.2 Pile testing under under lateral load<\/strong><\/h4>\n\n\n\nTo check the ultimate limit state of ground strength and the service limit state for allowable displacements of the structures, lateral load tests will be carried out with several embedment lengths, Li, to determine the necessary project embedment to support the design lateral load with adequate safety against ground-breaking. This is to ensure that for all load combinations:<\/p>\n\n\n\n
\ud835\udc39<\/em>l,d<\/em> <\/em>\u2264<\/em> <\/em>\ud835\udc45<\/em>l,d<\/em><\/em><\/p>\n\n\n\nWhere:<\/p>\n\n\n\n
Fl,d = Factored lateral load that the pile transmits to the ground. Rl,d = Factored ground strength when subjected to a lateral load.<\/p>\n\n\n\n
The value of Rl,d is derived from the test with the corresponding reduction factor, and the value of Fl,d will be provided by the structural engineer.<\/p>\n\n\n\n
The maximum load that the test must reach shouldbe applied by load-unload steps, measuring for each load step the absolute relative displacement between the base of the pile and the ground, and for each unload step, the remnant displacement. Displacements will be measured using a micrometer, and the measurements should be taken as close as possible to ground level.<\/p>\n\n\n\n
It is recommended for the maximum load applied to be at least 120% of the lateral load, Fl,d ,value.<\/p>\n\n\n\n
As an example, figure 5 includes a lateral load test carried out in accordance with the guidelines indicated.<\/p>\n\n\n\nRegarding the height of load application, it should be such that for the maximum lateral load at the base of the pile, the concomitant bending moment with the lateral load considered is Md. In the absence of this data, it is recommended that the height of application of the load must be about 1,0 m, and no higher than 1,5 m for piles that are not made of rolled steel or do not have a symmetrical transverse section.<\/p>\n\n\n\n
It is important to remember that the objective of the test is to verify the ultimate limit state of the foundation to horizontal forces and ensure that the absolute and remanent displacements that occur in the foundation during the structure’s service life are allowable. In any case, the test can always provide, through back-analysis calculation, an equivalent horizontal subgrade reaction modulus of the ground for the considered embedment length. This can be used to check the foundation using specific software for any other combination of bending and shear moment actions transmitted to the ground (as long as it is for the same embedment length considered in the tests and calculations), or another type of cross-section but of similar dimensions.<\/p>\n\n\n\nAs for de Values of allowable horizontal displacements of the foundation, they will be defined by the sructural engineer and depend on the type of structure, modulation, loads, etc. Common values observed in different test procedures are in the order of 20 – 30 mm for absolute displacements and 10 mm for remaining displacements.<\/p>\n\n\n\n
Horizontal loads are generally higher and therefore more limiting in the design of structures with solar trackers. When PV plants are designed with fixed type panels, the lateral load is less limiting and the number of this type of test could be reduced. <\/p>\n\n\n\n
4.2.3 Pile testing under axial load<\/h4>\n\n\n\n To check the ultimate limit state of the ground strength for both tensile and compressive vertical loads, the test procedure is similar. Axial tensile force is usually more influential in this type of structure, although this should not be taken as a general rule.<\/p>\n\n\n\n
In the case of a pile subjected to lateral loading, the tests will be carried out with different embedment lengths, Li, in order to determine the optimum embedment to support the vertical loads with an adequate safety factor against pile-ground contact breaking, ensuring that for all load combinations:<\/p>\n\n\n\n
\ud835\udc39<\/em>t,d<\/em> <\/em>\u2264<\/em> <\/em>\ud835\udc45<\/em>t,d<\/em> <\/em>\ud835\udc4e\ud835\udc5b\ud835\udc51<\/em> \ud835\udc39<\/em>c,d<\/em> <\/em>\u2264<\/em> <\/em>\ud835\udc45<\/em>c,d<\/em><\/em><\/p>\n\n\n\nWhere:<\/p>\n\n\n\n
Ft,d y Fc,d = Factored tensile and compression loads that the pile transmits to the ground.<\/p>\n\n\n\n
Rt,d y Rc,d = Factored ground strength when subjected to a vertical tensile and compression load.<\/p>\n\n\n\n
The values Rt, d and Rc,d are derived from the tests, and the values of Ft, d and Fc, d will have to be provided by the structural engineer.<\/p>\n\n\n\n
Tensile or compressive forces are applied to the top of the driven pile, and the displacements obtained in each load step must be measured to study the service limit state of allowable displacements of the structure. Figure 7 includes an example of a vertical tensile load test conducted according to the guidelines indicated.<\/p>\n\n\n\nFig. 7: Example of load-displacement curve for an axial tensile test<\/em><\/p>\n\n\n\nIt is recommended to apply the load until the pile is removed in uplift tests in order to determine the ultimate ground strength for the tensile reaction. If this is not achieved, the tests will be carried out until reaching the maximum load capacity that the reaction or the measurement equipment can provide.<\/p>\n\n\n\n
It is usual to consider only axial tensile load tests in the campaigns because they are usually more limiting for the dimensioning of the structure. Additionally, both in technical bibliography and in various foundation standards and guides, it is common to find the relationship between the resistance per shaft for tensile and compression forces:<\/p>\n\n\n\n
\ud835\udc45<\/em>tensile <\/em>= (0,60 \ud835\udc61\ud835\udc5c 0,70) \u00d7 \ud835\udc45<\/em>compression<\/em><\/em>4. REPORT<\/h4>\n\n\n\n The scope of a report of this type must be set between the technical test team and their client and can vary greatly, from a simple report summarizing the obtained results (\u201cfactual report\u201d) to a much more comprehensive report analyzing the results in-depth and pre-sizing the foundation (\u201cengineering report\u201d). The scope of the report must be defined in the conditions of the agreement.<\/p>\n\n\n\n
The factual report must include, at least, the following information:<\/p>\n\n\n\n
\nBackground, scope of the report, location of the studied area, site description, technical bibliography and any other available information useful for carrying out the works.<\/li>\n\n\n\n Site description and ground conditions.<\/span><\/li>\n\n\n\nGeometry and resistant characteristics of the piles used.<\/span><\/li>\n\n\n\nDescription of the pile driving machine, loading devices, reaction system and measuring equipment.<\/span><\/li>\n\n\n\nData of the pile driving such as: embedment length, driving time by representative sections, auxiliary works done for pile driving (pre-drilling, material used for filling the pre-drilling hole, etc.).<\/span><\/li>\n\n\n\nResults of the tests, both numerical (time, loads and displacements) and graphical representations (load-displacement curves).<\/li>\n<\/ul>\n\n\n\nIn the case of engineering report its content should be expanded to include at least:<\/p>\n\n\n\n
\nAnalysis and calculation of the characteristic parameters that govern the ground behavior for axial and lateral loads.<\/li>\n\n\n\n Setting the ultimate ground strength for the most unfavorable load combinations.<\/span><\/li>\n\n\n\nAnalysis of the serviceability limit state for the allowable foundation displacements.<\/span><\/li>\n\n\n\nZoning the site based on the statistical analysis of the test results.<\/span><\/li>\n\n\n\nPre-sizing the foundation for each identified area.<\/span><\/li>\n\n\n\nEstimation of performance of the driving works.<\/li>\n<\/ul>\n\n\n\nFinally, it is important to emphasize that the testing areas must be representative of the plant construction, taking particular care in areas with landfills.<\/p>\n\n\n\n
<\/p>","protected":false},"excerpt":{"rendered":"
Despu\u00e9s de adquirir experiencia en m\u00e1s de 35GW de plantas fotovoltaicas estudiadas en los cinco continentes, el Departamento de In Situ Test […]<\/p>","protected":false},"author":3,"featured_media":2243,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-2758","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-publicaciones"],"_links":{"self":[{"href":"https:\/\/orbisterrarum.es\/en\/wp-json\/wp\/v2\/posts\/2758","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/orbisterrarum.es\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/orbisterrarum.es\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/orbisterrarum.es\/en\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/orbisterrarum.es\/en\/wp-json\/wp\/v2\/comments?post=2758"}],"version-history":[{"count":1,"href":"https:\/\/orbisterrarum.es\/en\/wp-json\/wp\/v2\/posts\/2758\/revisions"}],"predecessor-version":[{"id":2760,"href":"https:\/\/orbisterrarum.es\/en\/wp-json\/wp\/v2\/posts\/2758\/revisions\/2760"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/orbisterrarum.es\/en\/wp-json\/wp\/v2\/media\/2243"}],"wp:attachment":[{"href":"https:\/\/orbisterrarum.es\/en\/wp-json\/wp\/v2\/media?parent=2758"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/orbisterrarum.es\/en\/wp-json\/wp\/v2\/categories?post=2758"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/orbisterrarum.es\/en\/wp-json\/wp\/v2\/tags?post=2758"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
![\"\"](\"https:\/\/orbisterrarum.es\/wp-content\/uploads\/2023\/03\/image-1-1024x704.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/orbisterrarum.es\/wp-content\/uploads\/2023\/03\/image-2-1024x715.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/orbisterrarum.es\/wp-content\/uploads\/2023\/03\/image-3.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/orbisterrarum.es\/wp-content\/uploads\/2023\/03\/image-8.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/orbisterrarum.es\/wp-content\/uploads\/2023\/03\/image-10.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/orbisterrarum.es\/wp-content\/uploads\/2023\/03\/image-9.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/orbisterrarum.es\/wp-content\/uploads\/2023\/03\/Captura-de-pantalla-2026-04-13-170623.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/orbisterrarum.es\/wp-content\/uploads\/2023\/03\/Imagen2-1024x708.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/orbisterrarum.es\/wp-content\/uploads\/2026\/04\/Captura-de-pantalla-2026-04-14-132414.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/orbisterrarum.es\/wp-content\/uploads\/2023\/03\/Imagen4-1024x742.png\")
<\/figure>\n\n\n\n