{"id":3461,"date":"2026-11-07T21:26:18","date_gmt":"2026-11-07T21:26:18","guid":{"rendered":"https:\/\/fenzemin.com\/?page_id=3461"},"modified":"2026-11-09T16:00:50","modified_gmt":"2026-11-09T16:00:50","slug":"istanbul-ground-conditions","status":"publish","type":"page","link":"https:\/\/fenzemin.com\/en\/knowledge-centre\/istanbul-ground-conditions\/","title":{"rendered":"Istanbul Ground Conditions and Deep Excavation Guide"},"content":{"rendered":"\n<div class=\"wp-block-group alignfull fz-home fz-svc is-layout-flow wp-block-group-is-layout-flow\">\n<section class=\"wp-block-group fz-page-hero fz-svc-hero is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group fz-wrap fz-svc-hero-grid is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group fz-svc-hero-text is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-eyebrow wp-block-paragraph\"><a href=\"https:\/\/fenzemin.com\/en\/knowledge-centre\/\">Knowledge Centre<\/a> \u00b7 Guide \u00b7 Istanbul ground conditions<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">Istanbul Ground Conditions: Deep Excavation Area by Area<\/h1>\n\n\n\n<p class=\"fz-lead wp-block-paragraph\">Istanbul ground conditions change within a few kilometres: soft sediment and fill along the Golden Horn, swelling clays to the west, fractured rock to the north and on the Asian side. In this guide we describe, area by area, the problems that come up most often in deep excavations and foundations, the usual solutions and examples from our own sites.<\/p>\n\n\n\n<div class=\"wp-block-buttons is-layout-flex wp-block-buttons-is-layout-flex\">\n<div class=\"wp-block-button fz-btn-primary\"><a class=\"wp-block-button__link wp-element-button\" href=\"https:\/\/fenzemin.com\/en\/request-a-quote\/\">Request a Quote<\/a><\/div>\n\n\n\n<div class=\"wp-block-button fz-btn-ghost\"><a class=\"wp-block-button__link wp-element-button\" href=\"tel:+905369327494\">+90 536 932 74 94<\/a><\/div>\n<\/div>\n<\/div>\n\n\n\n<figure class=\"wp-block-image size-large fz-hero-img\"><img decoding=\"async\" width=\"576\" height=\"1024\" data-no-lazy=\"1\" data-skip-lazy=\"1\" src=\"https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/karakoy-deniz-seviyesi-alti-kuru-kazi-tabani-2024-576x1024.jpg\" alt=\"Istanbul ground conditions and deep excavation: a dry excavation base about 4 m below sea level in Karak\u00f6y, 2024\" class=\"wp-image-3076\" srcset=\"https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/karakoy-deniz-seviyesi-alti-kuru-kazi-tabani-2024-576x1024.jpg 576w, https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/karakoy-deniz-seviyesi-alti-kuru-kazi-tabani-2024-169x300.jpg 169w, https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/karakoy-deniz-seviyesi-alti-kuru-kazi-tabani-2024-768x1365.jpg 768w, https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/karakoy-deniz-seviyesi-alti-kuru-kazi-tabani-2024-864x1536.jpg 864w, https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/karakoy-deniz-seviyesi-alti-kuru-kazi-tabani-2024.jpg 900w\" sizes=\"(max-width: 576px) 100vw, 576px\" \/><figcaption class=\"wp-element-caption\">Karak\u00f6y, 2024 \u00b7 dry excavation base about 4 m below sea level<\/figcaption><\/figure>\n<\/div>\n<\/section>\n\n\n\n<section class=\"wp-block-group fz-svc-facts is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group fz-wrap is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group fz-keyfacts is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group fz-keyfact is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-keyfact-label wp-block-paragraph\">Topic<\/p>\n\n\n\n<p class=\"fz-keyfact-value wp-block-paragraph\">Ground and deep excavation in Istanbul<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group fz-keyfact is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-keyfact-label wp-block-paragraph\">Reading time<\/p>\n\n\n\n<p class=\"fz-keyfact-value wp-block-paragraph\">About 8 minutes<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group fz-keyfact is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-keyfact-label wp-block-paragraph\">Written by<\/p>\n\n\n\n<p class=\"fz-keyfact-value wp-block-paragraph\">Abdullah \u00c7etinta\u015f, Geological Engineer<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group fz-keyfact is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-keyfact-label wp-block-paragraph\">Updated<\/p>\n\n\n\n<p class=\"fz-keyfact-value wp-block-paragraph\">November 2026<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group fz-keyfact is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-keyfact-label wp-block-paragraph\">Based on<\/p>\n\n\n\n<p class=\"fz-keyfact-value wp-block-paragraph\">Peer-reviewed papers and our site experience<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group fz-keyfact is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-keyfact-label wp-block-paragraph\">Examples<\/p>\n\n\n\n<p class=\"fz-keyfact-value wp-block-paragraph\">Karak\u00f6y and K\u00fc\u00e7\u00fck\u00e7ekmece<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n\n\n\n<section class=\"wp-block-group fz-sec fz-svc-main is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group fz-wrap fz-svc-layout is-layout-flow wp-block-group-is-layout-flow\">\n<nav class=\"wp-block-group fz-svc-toc is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-toc-title wp-block-paragraph\">In this guide<\/p>\n\n\n\n<ul class=\"wp-block-list fz-toc-list\">\n<li><a href=\"#overview\">Why so variable?<\/a><\/li>\n\n\n\n<li><a href=\"#summary\">Area by area<\/a><\/li>\n\n\n\n<li><a href=\"#coast\">Golden Horn and coast<\/a><\/li>\n\n\n\n<li><a href=\"#valleys\">Stream valleys<\/a><\/li>\n\n\n\n<li><a href=\"#west\">Western clays<\/a><\/li>\n\n\n\n<li><a href=\"#limestone\">Limestone areas<\/a><\/li>\n\n\n\n<li><a href=\"#rock\">Rock zones<\/a><\/li>\n\n\n\n<li><a href=\"#investigation\">Site investigation<\/a><\/li>\n\n\n\n<li><a href=\"#faq\">FAQ<\/a><\/li>\n<\/ul>\n<\/nav>\n\n\n\n<div class=\"wp-block-group fz-svc-content is-layout-flow wp-block-group-is-layout-flow\">\n<h2 class=\"wp-block-heading\" id=\"overview\">Why are Istanbul ground conditions so variable?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Under the city, units of very different ages and behaviour sit side by side. On the European side, for example, younger clay, sand and limestone layers lie on top of older, fractured rock. Along the coast and in stream beds, in turn, soft sediment and fill cover them.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A 2016 study by Dalg\u0131\u00e7 and colleagues lists the main conditions that cause foundation problems on the European side. These include low bearing capacity and settlement in young deposits, swelling and earthquake amplification in clayey units, thick fill along the shore and weathering and discontinuities in the rock units.<\/p>\n\n\n\n<div class=\"wp-block-group fz-svc-note is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Important:<\/strong> this guide shows general trends. Even within one district the ground changes from plot to plot; that is why a site-specific investigation always makes the final call.<\/p>\n<\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"summary\">Istanbul ground conditions: a summary by area<\/h2>\n\n\n\n<figure class=\"wp-block-table fz-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Area<\/th><th>Dominant ground<\/th><th>Common problem<\/th><th>Usual solution<\/th><\/tr><\/thead><tbody><tr><td>Golden Horn and the coast<\/td><td>Soft marine sediment and man-made fill<\/td><td>Water inflow, bore collapse, low bearing capacity<\/td><td>Secant piles, jet grout base, cased drilling<\/td><\/tr><tr><td>Stream valleys<\/td><td>Young alluvium: loose sand, silt, organic clay<\/td><td>Settlement, shallow groundwater, liquefaction risk<\/td><td>Piled foundations or ground improvement<\/td><\/tr><tr><td>Western clays<\/td><td>Clayey units such as the G\u00fcng\u00f6ren Formation<\/td><td>Swelling, differential settlement, landslides<\/td><td>Long anchors, drainage, staged excavation<\/td><\/tr><tr><td>Limestone areas<\/td><td>Alternating limestone, marl and clay<\/td><td>Solution cavities, marl softening with water<\/td><td>Close-spaced boreholes, tracking concrete use in drilling<\/td><\/tr><tr><td>European side rock zone<\/td><td>Trakya Formation: sandstone, siltstone, shale<\/td><td>Weathering, sliding along joints, dykes<\/td><td>Anchored walls, soil nailing, rock-socketed piles<\/td><\/tr><tr><td>Asian side rock zone<\/td><td>Palaeozoic sandstone, shale, quartzite, limestone<\/td><td>Fractured rock, shale weathering, hard quartzite<\/td><td>Soil nailing, anchors, suitable drilling tools<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"coast\">The Golden Horn and the coast: soft sediment, fill and water<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Soft marine sediment lies along the shores of the Golden Horn (Hali\u00e7). For example, in boreholes between Unkapan\u0131 and Azapkap\u0131, Meri\u00e7 and colleagues found Holocene deposits between 14 and 30 m thick. Dalg\u0131\u00e7 and colleagues also point to the thick fill along the shoreline.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Here the groundwater sits at sea level. So water is the main problem in excavation: it comes in through the base and the sides, and unsupported bores collapse. In addition, old building debris such as brick and rubble can turn up in the fill.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In Karak\u00f6y, for instance, we built a secant bored pile wall on a narrow waterfront plot and sealed the base with jet grouting. As a result, the contractor could build the foundation in a dry excavation about 4 m below sea level.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"valleys\">Stream valleys: young alluvium and liquefaction risk<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Young stream deposits, in other words alluvium, fill the floors of valleys such as Kurba\u011fal\u0131dere in Kad\u0131k\u00f6y and the Ayamama and Ka\u011f\u0131thane streams on the European side. These layers can contain loose sand, silt and organic clay. Also, the groundwater is usually shallow.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Dalg\u0131\u00e7 and colleagues note that young deposits such as alluvium and fill can lack bearing capacity and cause settlement problems. In addition, saturated loose sand carries a liquefaction risk in an earthquake. Therefore, a liquefaction assessment under the Turkish Building Earthquake Code (TBDY 2018) matters especially on these sites.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The usual solution is a piled foundation or ground improvement such as <a href=\"https:\/\/fenzemin.com\/en\/services\/jet-grouting\/\">jet grouting<\/a> or deep soil mixing. During excavation, however, you also need cased drilling and a water management plan.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">We also explain in short videos how alluvium behaves in an earthquake and what liquefaction is. However, the footage may be sample material for educational purposes.<\/p>\n\n\n\n<div class=\"wp-block-group fz-videos fz-videos--svc is-layout-flow wp-block-group-is-layout-flow\"><figure class=\"fz-yt-wrap\"><a class=\"fz-yt\" href=\"https:\/\/www.youtube.com\/watch?v=0Wmdv1Y8878\" data-id=\"0Wmdv1Y8878\" data-title=\"Earthquake behaviour of rock and alluvium\" aria-label=\"Play video: Earthquake behaviour of rock and alluvium\" target=\"_blank\" rel=\"noopener\"><img src=\"https:\/\/i.ytimg.com\/vi\/0Wmdv1Y8878\/hqdefault.jpg\" alt=\"Earthquake behaviour of rock and alluvium\" width=\"480\" height=\"360\" loading=\"lazy\" decoding=\"async\"><span class=\"fz-yt-play\" aria-hidden=\"true\"><\/span><\/a><figcaption>Earthquake behaviour of rock and alluvium <small>In Turkish; may include sample footage for educational purposes<\/small><\/figcaption><\/figure>\n\n\n<figure class=\"fz-yt-wrap\"><a class=\"fz-yt\" href=\"https:\/\/www.youtube.com\/watch?v=GDp_aFUaMZw\" data-id=\"GDp_aFUaMZw\" data-title=\"What is soil liquefaction?\" aria-label=\"Play video: What is soil liquefaction?\" target=\"_blank\" rel=\"noopener\"><img src=\"https:\/\/i.ytimg.com\/vi\/GDp_aFUaMZw\/hqdefault.jpg\" alt=\"What is soil liquefaction?\" width=\"480\" height=\"360\" loading=\"lazy\" decoding=\"async\"><span class=\"fz-yt-play\" aria-hidden=\"true\"><\/span><\/a><figcaption>What is soil liquefaction? <small>In Turkish; may include sample footage for educational purposes<\/small><\/figcaption><\/figure>\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\">You can find all our videos on our <a href=\"https:\/\/www.youtube.com\/@fenzemin\" target=\"_blank\" rel=\"noopener\">YouTube<\/a> and <a href=\"https:\/\/www.instagram.com\/fenzemin\/\" target=\"_blank\" rel=\"noopener\">Instagram<\/a> accounts.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"west\">The western districts: swelling clays and landslides<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Clay-rich units such as the G\u00fcng\u00f6ren Formation are widespread around Avc\u0131lar, K\u00fc\u00e7\u00fck\u00e7ekmece and Beylikd\u00fcz\u00fc. According to Dalg\u0131\u00e7 and colleagues, these units can cause earthquake amplification, swelling and differential settlement.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">There are also landslides on the slopes between the two lakes; Dalg\u0131\u00e7, Turgut and Ku\u015fku studied the factors that prepare and trigger them. For this reason, drainage and slope stability analysis matter in sloped excavations.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In clay, an anchor&#8217;s bond length transfers less friction than in sandy ground; consequently, anchors get longer. In the deep excavation in K\u00fc\u00e7\u00fck\u00e7ekmece, for example, we supported a wall of 200 bored piles with 800 prestressed anchors in clay. The total anchor length reached 30,000 m.<\/p>\n\n\n\n<figure data-wp-context=\"{&quot;imageId&quot;:&quot;6af20181615c5&quot;}\" data-wp-interactive=\"core\/image\" data-wp-key=\"6af20181615c5\" class=\"wp-block-image size-large wp-lightbox-container\"><img decoding=\"async\" width=\"768\" height=\"1024\" data-wp-class--hide=\"state.isContentHidden\" data-wp-class--show=\"state.isContentVisible\" data-wp-init=\"callbacks.setButtonStyles\" data-wp-on--click=\"actions.showLightbox\" data-wp-on--load=\"callbacks.setButtonStyles\" data-wp-on--pointerdown=\"actions.preloadImage\" data-wp-on--pointerenter=\"actions.preloadImageWithDelay\" data-wp-on--pointerleave=\"actions.cancelPreload\" data-wp-on-window--resize=\"callbacks.setButtonStyles\" src=\"https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/kucukcekmece-fore-kazikli-ankrajli-iksa-2023-768x1024.jpg\" alt=\"K\u00fc\u00e7\u00fck\u00e7ekmece, 2023: bored pile wall with many rows of prestressed anchors in clay\" class=\"wp-image-3016\" srcset=\"https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/kucukcekmece-fore-kazikli-ankrajli-iksa-2023-768x1024.jpg 768w, https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/kucukcekmece-fore-kazikli-ankrajli-iksa-2023-225x300.jpg 225w, https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/kucukcekmece-fore-kazikli-ankrajli-iksa-2023.jpg 1080w\" sizes=\"(max-width: 768px) 100vw, 768px\" \/><button\n\t\t\tclass=\"lightbox-trigger\"\n\t\t\ttype=\"button\"\n\t\t\taria-haspopup=\"dialog\"\n\t\t\tdata-wp-bind--aria-label=\"state.thisImage.triggerButtonAriaLabel\"\n\t\t\tdata-wp-init=\"callbacks.initTriggerButton\"\n\t\t\tdata-wp-on--click=\"actions.showLightbox\"\n\t\t\tdata-wp-style--right=\"state.thisImage.buttonRight\"\n\t\t\tdata-wp-style--top=\"state.thisImage.buttonTop\"\n\t\t>\n\t\t\t<svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"12\" height=\"12\" fill=\"none\" viewBox=\"0 0 12 12\">\n\t\t\t\t<path fill=\"#fff\" d=\"M2 0a2 2 0 0 0-2 2v2h1.5V2a.5.5 0 0 1 .5-.5h2V0H2Zm2 10.5H2a.5.5 0 0 1-.5-.5V8H0v2a2 2 0 0 0 2 2h2v-1.5ZM8 12v-1.5h2a.5.5 0 0 0 .5-.5V8H12v2a2 2 0 0 1-2 2H8Zm2-12a2 2 0 0 1 2 2v2h-1.5V2a.5.5 0 0 0-.5-.5H8V0h2Z\" \/>\n\t\t\t<\/svg>\n\t\t<\/button><figcaption class=\"wp-element-caption\">K\u00fc\u00e7\u00fck\u00e7ekmece, 2023 \u00b7 anchored wall in clay<\/figcaption><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"limestone\">Limestone areas: cavities and marl<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Alternating limestone, marl and clay are common around Bak\u0131rk\u00f6y and Zeytinburnu. Limestone can contain solution cavities; for example, Dalg\u0131\u00e7 and colleagues point to karst cavity zones in the Eocene K\u0131rklareli Formation.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Drilling into a sudden cavity means a sudden jump in concrete use. That is why these areas call for close-spaced boreholes and for tracking concrete use pile by pile during drilling. Also, marl can soften on contact with water; as a result, drainage and waterproofing become important in basements.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"rock\">Rock zones: weathering, joints and hard drilling<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Sandstone, siltstone and shale of the Trakya Formation underlie the area around Beyo\u011flu, \u015ei\u015fli, Be\u015fikta\u015f, Ka\u011f\u0131thane and Sar\u0131yer. Dalg\u0131\u00e7 and colleagues note that weathering, discontinuities and dykes can cause problems in these rocks. In other words, rock quality can change from metre to metre.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The most common problem in excavation is rock wedges sliding along joints and bedding planes. So as the dig goes on, you need to check the orientation of discontinuities and support the face quickly with anchors, <a href=\"https:\/\/fenzemin.com\/en\/services\/soil-nailing\/\">soil nails<\/a> and shotcrete.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">On the Asian side, by contrast, Palaeozoic sandstone, shale, quartzite and limestone units occur around \u00dcmraniye, Ata\u015fehir, Kartal and Pendik. Shale can weather quickly once exposed to air and water; for this reason, you should not leave the excavation face open for long. Quartzite, on the other hand, is very hard and abrasive, so we choose drilling tools to suit it.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"investigation\">Istanbul ground conditions and the site investigation<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">This table is a starting point, but the site investigation decides the project. That is because fill thickness, depth to rock and groundwater can change even within one street.<\/p>\n\n\n\n<figure data-wp-context=\"{&quot;imageId&quot;:&quot;6af2018161ec3&quot;}\" data-wp-interactive=\"core\/image\" data-wp-key=\"6af2018161ec3\" class=\"wp-block-image size-full fz-figure wp-lightbox-container\"><img decoding=\"async\" data-wp-class--hide=\"state.isContentHidden\" data-wp-class--show=\"state.isContentVisible\" data-wp-init=\"callbacks.setButtonStyles\" data-wp-on--click=\"actions.showLightbox\" data-wp-on--load=\"callbacks.setButtonStyles\" data-wp-on--pointerdown=\"actions.preloadImage\" data-wp-on--pointerenter=\"actions.preloadImageWithDelay\" data-wp-on--pointerleave=\"actions.cancelPreload\" data-wp-on-window--resize=\"callbacks.setButtonStyles\" src=\"https:\/\/fenzemin.com\/wp-content\/plugins\/fenzemin-core\/assets\/img\/sondaj-kesit-en.svg?v=1\" alt=\"Site investigation that shows Istanbul ground conditions at plot scale: borehole, SPT, sampling, coring and groundwater\"\/><button\n\t\t\tclass=\"lightbox-trigger\"\n\t\t\ttype=\"button\"\n\t\t\taria-haspopup=\"dialog\"\n\t\t\tdata-wp-bind--aria-label=\"state.thisImage.triggerButtonAriaLabel\"\n\t\t\tdata-wp-init=\"callbacks.initTriggerButton\"\n\t\t\tdata-wp-on--click=\"actions.showLightbox\"\n\t\t\tdata-wp-style--right=\"state.thisImage.buttonRight\"\n\t\t\tdata-wp-style--top=\"state.thisImage.buttonTop\"\n\t\t>\n\t\t\t<svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"12\" height=\"12\" fill=\"none\" viewBox=\"0 0 12 12\">\n\t\t\t\t<path fill=\"#fff\" d=\"M2 0a2 2 0 0 0-2 2v2h1.5V2a.5.5 0 0 1 .5-.5h2V0H2Zm2 10.5H2a.5.5 0 0 1-.5-.5V8H0v2a2 2 0 0 0 2 2h2v-1.5ZM8 12v-1.5h2a.5.5 0 0 0 .5-.5V8H12v2a2 2 0 0 1-2 2H8Zm2-12a2 2 0 0 1 2 2v2h-1.5V2a.5.5 0 0 0-.5-.5H8V0h2Z\" \/>\n\t\t\t<\/svg>\n\t\t<\/button><figcaption class=\"wp-element-caption\">Site-specific investigation and drilling, schematic drawing.<\/figcaption><\/figure>\n\n\n\n<ol class=\"wp-block-list fz-svc-steps\">\n<li><strong>Boreholes:<\/strong> should go deeper than the excavation and the piles.<\/li>\n\n\n\n<li><strong>Groundwater:<\/strong> measure the level and assess it for the excavation period.<\/li>\n\n\n\n<li><strong>Laboratory:<\/strong> swelling in clay, strength and discontinuity data in rock.<\/li>\n\n\n\n<li><strong>Earthquake:<\/strong> ground class under TBDY 2018 and, where needed, liquefaction analysis.<\/li>\n\n\n\n<li><strong>Adjacent buildings:<\/strong> the depth and condition of neighbouring foundations.<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">If you do not have a site investigation yet, we can arrange one <a href=\"https:\/\/fenzemin.com\/en\/services\/site-investigation\/\">together with our drilling partner<\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"faq\">Frequently asked questions about Istanbul ground conditions<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">We have collected the questions about ground in Istanbul that we hear most often. However, if yours is not here, call us or write through the quote form.<\/p>\n\n\n\n<h3 class=\"wp-block-heading fz-faq-group\">Istanbul ground conditions by area<\/h3>\n\n\n\n<div class=\"wp-block-group fz-faq-list fz-faq-list--svc is-layout-flow wp-block-group-is-layout-flow\">\n<details class=\"wp-block-details fz-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>Where is the firmest ground in Istanbul?<\/summary>\n<p class=\"wp-block-paragraph\">In general, areas where rock lies close to the surface cause fewer problems. However, weathering and joints can be a problem in rock too. That is why you should look at the site investigation, not the name of the district.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details fz-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>Is the ground on the European side bad?<\/summary>\n<p class=\"wp-block-paragraph\">No, that generalisation is wrong. The European side has both firm rock and soft sediment. A site-specific investigation makes the call.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details fz-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>Can you build a basement on the waterfront?<\/summary>\n<p class=\"wp-block-paragraph\">Yes, but you need shoring that cuts off the water. In Karak\u00f6y, for example, secant piles and a jet grout base made it possible to build the foundation in a dry excavation about 4 m below sea level.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details fz-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>What does swelling clay do to a building?<\/summary>\n<p class=\"wp-block-paragraph\">Clay swells as it takes on water and shrinks as it dries. This movement can cause differential settlement and cracks in the foundation. Therefore, drainage and a suitable foundation depth matter on clay sites.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details fz-faq is-layout-flow wp-block-details-is-layout-flow\"><summary>Can a map of Istanbul ground conditions replace a site investigation?<\/summary>\n<p class=\"wp-block-paragraph\">No. Maps such as microzonation studies show general trends; however, you still need to design the project with site-specific borehole and laboratory data.<\/p>\n<\/details>\n<\/div>\n\n\n\n<div class=\"wp-block-group fz-author is-layout-flow wp-block-group-is-layout-flow\">\n<figure class=\"wp-block-image size-medium fz-author-img\"><img decoding=\"async\" width=\"300\" height=\"300\" src=\"https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/abdullah-cetintas-jeoloji-muhendisi-300x300.jpg\" alt=\"Abdullah \u00c7etinta\u015f, Geological Engineer, founder of Fen Zemin &#038; \u0130n\u015faat\" class=\"wp-image-3026\" srcset=\"https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/abdullah-cetintas-jeoloji-muhendisi-300x300.jpg 300w, https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/abdullah-cetintas-jeoloji-muhendisi-150x150.jpg 150w, https:\/\/fenzemin.com\/wp-content\/uploads\/2026\/11\/abdullah-cetintas-jeoloji-muhendisi.jpg 640w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/figure>\n\n\n\n<div class=\"wp-block-group fz-author-body is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-author-name wp-block-paragraph\"><strong>Abdullah \u00c7etinta\u015f<\/strong><\/p>\n\n\n\n<p class=\"fz-author-role wp-block-paragraph\">Geological Engineer \u00b7 Founder, Fen Zemin &amp; \u0130n\u015faat<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In ground engineering and foundations since 2006. This guide draws on peer-reviewed sources and on our team&#8217;s site experience in Istanbul.<\/p>\n\n\n\n<p class=\"fz-author-meta wp-block-paragraph\"><a href=\"https:\/\/www.linkedin.com\/in\/abdullahcetintas\/\" target=\"_blank\" rel=\"noopener\">LinkedIn profile<\/a> \u00b7 Last updated: November 2026<\/p>\n<\/div>\n<\/div>\n\n\n\n<h2 class=\"wp-block-heading fz-sources-title\" id=\"sources\">Sources<\/h2>\n\n\n\n<ul class=\"wp-block-list fz-sources\">\n<li><a href=\"https:\/\/dergipark.org.tr\/tr\/pub\/uybd\/article\/240201\" target=\"_blank\" rel=\"noopener\">Dalg\u0131\u00e7, S. et al. (2016). The effect of soil and rock conditions on construction foundations on the European side of Istanbul. Uygulamal\u0131 Yerbilimleri Dergisi, 8(2), 47\u201370 (in Turkish)<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/research.itu.edu.tr\/en\/publications\/hali%C3%A7-istanbul-kiyi-alanlarinda-unkapani-azapkapi-g%C3%B6zlenen-holose\/\" target=\"_blank\" rel=\"noopener\">Meri\u00e7, E. et al. (2003). New findings on the Holocene deposits in the Golden Horn (Istanbul) coastal area (Unkapan\u0131\u2013Azapkap\u0131). Yerbilimleri, 28, 9\u201332<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/dergipark.org.tr\/en\/download\/article-file\/208601\" target=\"_blank\" rel=\"noopener\">Dalg\u0131\u00e7, S., Turgut, M. and Ku\u015fku, \u0130. The Evaluation of Preparative and Triggering Parameters on Occurrence of Landslides in the B\u00fcy\u00fck\u00e7ekmece\u2013K\u00fc\u00e7\u00fck\u00e7ekmece (DergiPark)<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/section>\n\n\n\n<section class=\"wp-block-group fz-sec fz-sec--soft fz-svc-related is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group fz-wrap is-layout-flow wp-block-group-is-layout-flow\">\n<h2 class=\"wp-block-heading\">Related pages<\/h2>\n\n\n\n<div class=\"wp-block-group fz-related-grid is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group fz-related-card is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-related-title wp-block-paragraph\"><a href=\"https:\/\/fenzemin.com\/en\/services\/site-investigation\/\">Site Investigation<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Site-specific boreholes<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group fz-related-card is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-related-title wp-block-paragraph\"><a href=\"https:\/\/fenzemin.com\/en\/services\/bored-piles\/\">Bored Piles<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Secant and anchored walls<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group fz-related-card is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-related-title wp-block-paragraph\"><a href=\"https:\/\/fenzemin.com\/en\/services\/jet-grouting\/\">Jet Grouting<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Water cut-off on the coast<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group fz-related-card is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-related-title wp-block-paragraph\"><a href=\"https:\/\/fenzemin.com\/en\/services\/ground-anchors\/\">Ground Anchors<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Long anchors in clay<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group fz-related-card is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-related-title wp-block-paragraph\"><a href=\"https:\/\/fenzemin.com\/en\/projects\/karakoy-eren-holding-office-building\/\">Karak\u00f6y project<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A foundation below sea level<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group fz-related-card is-layout-flow wp-block-group-is-layout-flow\">\n<p class=\"fz-related-title wp-block-paragraph\"><a href=\"https:\/\/fenzemin.com\/en\/projects\/kucukcekmece-aydin-university-annex\/\">K\u00fc\u00e7\u00fck\u00e7ekmece project<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Anchored shoring in clay<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n\n\n\n<section class=\"wp-block-group fz-sec fz-cta is-layout-flow wp-block-group-is-layout-flow\">\n<div class=\"wp-block-group fz-wrap fz-center is-layout-flow wp-block-group-is-layout-flow\">\n<h2 class=\"wp-block-heading\">Let us review the ground on your plot together<\/h2>\n\n\n\n<p class=\"fz-intro wp-block-paragraph\">Send us your site investigation and architectural design. Then let us discuss the excavation and foundation options together with our design partner.<\/p>\n\n\n\n<div class=\"wp-block-buttons fz-center-buttons is-layout-flex wp-block-buttons-is-layout-flex\">\n<div class=\"wp-block-button fz-btn-primary\"><a class=\"wp-block-button__link wp-element-button\" href=\"https:\/\/fenzemin.com\/en\/request-a-quote\/\">Request a Quote<\/a><\/div>\n\n\n\n<div class=\"wp-block-button fz-btn-dark\"><a class=\"wp-block-button__link wp-element-button\" href=\"tel:+905369327494\">+90 536 932 74 94<\/a><\/div>\n<\/div>\n<\/div>\n<\/section>\n<\/div>\n\n","protected":false},"excerpt":{"rendered":"<p>Knowledge Centre \u00b7 Guide \u00b7 Istanbul ground conditions Istanbul Ground Conditions: Deep Excavation Area by Area Istanbul ground conditions change within a few kilometres: soft sediment and fill along the Golden Horn, swelling clays to the west, fractured rock to the north and on the Asian side. In this guide we describe, area by area, [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":3077,"parent":3452,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_uag_custom_page_level_css":"","site-sidebar-layout":"default","site-content-layout":"page-builder","ast-site-content-layout":"full-width-container","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"disabled","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_joinchat":[],"footnotes":""},"class_list":["post-3461","page","type-page","status-publish","has-post-thumbnail","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Istanbul Ground Conditions: Deep Excavation Guide<\/title>\n<meta name=\"description\" content=\"Istanbul ground conditions change by area: Golden Horn shore, stream valleys, western clays and rock zones. 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