{"id":2957,"date":"2026-08-27T17:49:43","date_gmt":"2026-08-27T09:49:43","guid":{"rendered":"https:\/\/soilimprovementsz.com\/?p=2957"},"modified":"2026-08-27T17:49:44","modified_gmt":"2026-08-27T09:49:44","slug":"design-basis-and-control-requirements-for-vacuum-preloading-in-soft%e2%80%91ground-improvement","status":"publish","type":"post","link":"https:\/\/soilimprovementsz.com\/en_za\/design-basis-and-control-requirements-for-vacuum-preloading-in-soft%e2%80%91ground-improvement\/","title":{"rendered":"Design Basis and Control Requirements for Vacuum Preloading in Soft\u2011Ground Improvement"},"content":{"rendered":"

There are no universal fixed parameters for vacuum preloading design of soft\u2011ground improvement. Design shall be formulated on a project\u2011specific basis according to site geological conditions, design drawings, load grades, construction schedule and site conditions. Construction parameters and control criteria shall be adjusted targeting actual project conditions, so as to ensure ground improvement quality, settlement indicators and service safety comply with project design and specification requirements. General design requirements are specified as follows:<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

1\u3001Site Levelling Design Requirements<\/strong><\/p>\n\n\n\n

\uff081\uff09Prior to formal ground improvement construction, perform overall site levelling within the soft\u2011ground treatment zone. Remove uneven top\u2011soil and re\u2011grade terrain to provide a neat and flat working surface for subsequent PVD installation, sealing membrane laying and vacuum preloading operations.<\/p>\n\n\n\n

\uff082\uff09No fixed standard applies to site levelling. Adjust flexibly in accordance with special design documents and actual site conditions to adapt to construction requirements of different projects.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

2\u3001Ground Improvement Technology Design Requirements<\/strong><\/p>\n\n\n\n

\uff081\uff09Select the optimal soft\u2011ground improvement technology by comprehensive consideration of project geology, settlement control criteria and construction schedule. Prefabricated Vertical Drains (PVDs) combined with vacuum preloading consolidation is the mainstream general\u2011purpose technology.<\/p>\n\n\n\n

\uff082\uff09No fixed values are specified for technical parameters, improvement scope and construction control criteria. Conduct targeted optimisation and adjustment according to project design documents, soil\u2011layer distribution and soil properties to satisfy improvement demands of various projects.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

3\u3001<\/strong> Preloading Period and Unloading Confirmation Requirements<\/strong><\/strong><\/p>\n\n\n\n

\uff081\uff09The consolidation period of vacuum preloading shall be determined specially based on soft\u2011soil thickness, soil properties, consolidation difficulty and overall construction schedule, without a unified fixed duration.<\/p>\n\n\n\n

\uff082\uff09After the site reaches the designed vacuum degree, full\u2011load preloading shall be carried out. For conventional projects, the full\u2011load preloading duration shall be controlled at 90\u202fdays, which may be flexibly adjusted according to actual consolidation requirements.<\/p>\n\n\n\n

\uff083\uff09Before unloading, compile complete full\u2011process settlement\u2011monitoring data and consolidate acceptance documents. Unloading operations can only be implemented after joint verification and approval by the owner, designer, supervisor and constructor.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

4. Site Pre\u2011treatment and Elevation Control Requirements<\/strong><\/strong><\/p>\n\n\n\n

\uff081\uff09Before construction, thoroughly remove boulders, plant roots, sundries and weak interlayers within newly\u2011filled soil on site, so as to prevent adverse impacts of poor top\u2011soil on PVD installation quality and ground consolidation performance.<\/p>\n\n\n\n

\uff082\uff09After debris clearance, level the site to the designed elevation. Elevation deviation shall comply with project\u2011specific design and specification requirements.<\/p>\n\n\n\n

\uff083\uff09For conventional projects, the elevation tolerance shall be within 10\u202fcm. Precision requirements may be flexibly adjusted per design standards of different projects.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

5. PVD Design and Inspection Requirements<\/strong><\/strong><\/p>\n\n\n\n

\uff081\uff09Specifications, models and layout patterns of prefabricated vertical drains shall comply with special project drawings. SPB\u2011B or SPB\u2011C PVDs are commonly adopted, arranged in square or staggered (plum\u2011blossom) patterns. Spacing and penetration depth shall strictly follow profile and detail drawings, and may be optimised according to site geological conditions.<\/p>\n\n\n\n

\uff082\uff09 PVD quality shall satisfy the requirements of *Quality Inspection Standard for Prefabricated Vertical Drains* (JTS\/T 206\u20111\u20112023). Complete documents including factory certificates and manufacturer self\u2011inspection reports shall be provided upon material delivery.<\/p>\n\n\n\n

\uff083\uff09 Delivered materials shall be sampled and tested in accordance with specifications and project requirements. Materials can be put into site construction only after passing inspection by qualified third\u2011party testing institutions.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

6<\/strong>\u3001<\/strong> Site Drainage System Design Requirements<\/strong><\/strong><\/p>\n\n\n\n

\uff081\uff09Reasonably arrange peripheral open drainage ditches combining site topography, catchment conditions and construction layout plans.<\/p>\n\n\n\n

\uff082\uff09The dimension, alignment and density of open ditches shall be specially designed according to site scale. Water outlets shall be located at low\u2011lying areas of the site to guarantee smooth drainage.<\/p>\n\n\n\n

\uff083\uff09Improve the surface drainage system to avoid soft\u2011ground soaking caused by ponding, damage to vacuum sealing structure and deterioration of preloading\u2011consolidation performance. Drainage schemes may be flexibly optimised for actual site conditions.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

7<\/strong>\u3001<\/strong> Vacuum Degree and Consolidation Degree Control Requirements<\/strong><\/strong><\/p>\n\n\n\n

\uff081\uff09During vacuum preloading construction, vacuum under the membrane shall be distributed stably and uniformly. For conventional projects, vacuum degree shall be maintained above 650\u202fmmHg (80\u202fkPa); specific values shall follow special project\u2011design indicators.<\/p>\n\n\n\n

\uff082\uff09Before unloading, the average consolidation degree of soil layers within the PVD improvement depth shall meet design requirements, which shall exceed 90\u202f% for conventional projects.<\/p>\n\n\n\n

\uff083\uff09Indicators for vacuum degree and consolidation degree are not fixed, and shall be adjusted differentially according to settlement criteria and functional requirements of different projects.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

8. Pump\u2011off and Unloading Control Requirements<\/strong><\/strong><\/p>\n\n\n\n

\uff082\uff09 Pump\u2011off and unloading conditions for vacuum preloading shall comply with special project design. Unloading can be performed only after consolidation\u2011degree or settlement\u2011stability indicators are satisfied and confirmed by all participating parties.<\/p>\n\n\n\n

\uff082\uff09 Conventional settlement\u2011stability criterion: when the average measured settlement rate is \u2264\u202f2\u202fmm\/day for 7 consecutive days, the site is regarded as basically settlement\u2011stable; pump\u2011off and unloading operations can be conducted combined with consolidation\u2011degree results.<\/p>\n\n\n\n

\uff083\uff09Threshold values for settlement rate control may be flexibly adjusted according to foundation\u2011design grades and settlement\u2011limit requirements of different projects.<\/p>\n\n\n\n

\"soft<\/figure>\n\n\n\n

Source: <\/strong>Guangzhou Sunzo Foundation Engineering Co., Ltd.<\/strong><\/p>\n\n\n\n

Follow SUNZO for continuous updates on soft\u2011ground improvement knowledge, construction techniques, interpretation of new technologies and engineering case studies!<\/p>\n\n\n\n

<\/p>","protected":false},"excerpt":{"rendered":"

There are no universal fixed parameters for vacuum preloading design of soft\u2011ground improvement. Design shall be formulated on a project\u2011specific […]<\/p>\n","protected":false},"author":1,"featured_media":2968,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","_seopress_robots_follow":"","_seopress_robots_imageindex":"","_seopress_robots_snippet":"","_seopress_robots_primary_cat":"none","_seopress_robots_breadcrumbs":"","_seopress_robots_freeze_modified_date":"","_seopress_robots_custom_modified_date":"","_seopress_robots_canonical":"","_seopress_social_fb_title":"","_seopress_social_fb_desc":"","_seopress_social_fb_img":"","_seopress_social_fb_img_attachment_id":0,"_seopress_social_fb_img_width":0,"_seopress_social_fb_img_height":0,"_seopress_social_twitter_title":"","_seopress_social_twitter_desc":"","_seopress_social_twitter_img":"","_seopress_social_twitter_img_attachment_id":0,"_seopress_social_twitter_img_width":0,"_seopress_social_twitter_img_height":0,"_seopress_redirections_value":"","_seopress_redirections_enabled":"","_seopress_redirections_enabled_regex":"","_seopress_redirections_logged_status":"both","_seopress_redirections_param":"","_seopress_redirections_type":301,"_seopress_analysis_target_kw":"vacuum preloading,soft ground improvement,prefabricated vertical drain,PVD,soil consolidation,port engineering,and reclamation,geotechnical engineering,SUNZO,prefabricated vertical drain (PVD)","site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","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":"","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":"default","ast-page-background-enabled":"default","ast-page-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":"","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-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":"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":""},"mobile":{"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":""}},"footnotes":""},"categories":[1],"tags":[52,31,30,47],"class_list":["post-2957","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-foundation-engineering","tag-pvd-installation-barge","tag-soft-ground-improvement","tag-vacuum-preloading"],"_links":{"self":[{"href":"https:\/\/soilimprovementsz.com\/en_za\/wp-json\/wp\/v2\/posts\/2957","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/soilimprovementsz.com\/en_za\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/soilimprovementsz.com\/en_za\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/soilimprovementsz.com\/en_za\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/soilimprovementsz.com\/en_za\/wp-json\/wp\/v2\/comments?post=2957"}],"version-history":[{"count":1,"href":"https:\/\/soilimprovementsz.com\/en_za\/wp-json\/wp\/v2\/posts\/2957\/revisions"}],"predecessor-version":[{"id":2969,"href":"https:\/\/soilimprovementsz.com\/en_za\/wp-json\/wp\/v2\/posts\/2957\/revisions\/2969"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/soilimprovementsz.com\/en_za\/wp-json\/wp\/v2\/media\/2968"}],"wp:attachment":[{"href":"https:\/\/soilimprovementsz.com\/en_za\/wp-json\/wp\/v2\/media?parent=2957"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/soilimprovementsz.com\/en_za\/wp-json\/wp\/v2\/categories?post=2957"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/soilimprovementsz.com\/en_za\/wp-json\/wp\/v2\/tags?post=2957"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}