KNOWLEDGE · GROUND AND FOUNDATIONS

Ground and foundations: stabilisation, voids, lifting

These three tasks may use injection, but their objectives and acceptance criteria differ. Start with the cause of lost support, then select the material and structural monitoring method.

Assessment Procedure and options Selection and next step

EXPLORE THE METHOD

Ground and foundations: six access and distribution options

This is a set of options, not a list of six consecutive operations. The first two cross-sections show access beneath a foundation, the next two beneath a slab, and the last compare material outlets from a lance. First define the objective: consolidation, restoring support, designed lifting or a water barrier.

Cross-section of a wall, foundation and slab with angled lances from inside reaching the ground zone beneath the foundation. — The lance determines the injection location; the yellow zone represents the intended treatment area.

01 · Access beneath a foundation

Objective and option A: access beneath a foundation from inside

The material must reach the assessed layer beneath the foundation. The drawing relates the angle measured from the floor, entry offset from the wall, foundation underside level and working depth below it. Lance length is measured along its axis, so it is not equal to the vertical depth.

The 50% label indicates a reference point in the wall geometry shown; it does not determine the strengthening position for every foundation. The yellow shape guarantees neither coverage geometry nor improved bearing capacity. The objective and working layer must be established through structural and ground assessment.

Assess the foundation, slab and services.
Identify the target layer before calculating length.

Access geometry beneath a foundation →Assessment of lost support →

Lances run at an angle from ground level outside the wall into the zone below the foundation. — External access changes the entry point and angle reference.

02 · Access beneath a foundation

Option B: access beneath a foundation from outside

Here, the angle is measured from the ground surface and the entry offset from the external wall. Together with the foundation underside depth, they determine the lance path. Tips marked at different levels show possible injection zone positions, not a mandatory sequence of three injections.

Selecting outside access requires checking available space, services and layers beside the foundation. During injection, record uptake and monitor the structure. Unexpected lifting during stabilisation requires stopping; lifting must be a separately designed objective.

Check the angle reference to the ground.
Set stopping thresholds before the trial.

Trial and structural measurements →

Horizontal lances run from outside the wall into the zone beneath the slab; two length dimensions are shown. — The injection point is beneath the slab, while the access path passes through the wall zone.

03 · Access beneath a slab

Option C: beneath a slab using horizontal lances from outside

This option allows material to be injected into the space beneath a slab from outside. Identify its connections and the cause of lost support. The two length labels distinguish the shorter section beneath the slab from the longer access path to that location.

The 100 cm dimension in the illustration belongs to the lance arrangement shown; it is not ready-to-use spacing for every slab. Plan points and the injection zone based on a trial, and assess progress through structural observation and quantity records. Filling the nearest void does not prove improvement of deeper ground.

Establish whether the target is a void or a deeper soil layer.
Monitor possible migration beyond the slab perimeter.

Distinguishing injection objectives →GeoStabil →

Vertical lances pass through the slab to a yellow zone in the ground; point spacing is marked on the slab. — Drilling through the slab provides direct access to the assessed support zone.

04 · Access beneath a slab

Option D: beneath a slab through boreholes from inside

Before setting out points, identify slab thickness and layers, reinforcement and services. Lance tips must lie in the zone covered by the selected method. The 80–120 cm spacing is a parameter of the option shown; the actual grid must relate to the ground and trial results.

For void filling and stabilisation, monitor for unintended slab lifting. If lifting is the objective, target levels, allowable differential movements and measurements during injection are required. Material expansion may continue after the pump stops.

Set out points accounting for services.
Measure displacement independently of consumption.

GeoPolymer.55: system selection →Trial and stopping criteria →

Lances with an opening tip at the end; arrows show material discharge in the zone beneath the foundation. — The end outlet locates injection at the lance tip.

05 · Material outlet method

Lance option: injection through an opening tip

In this option, the tip opens according to the system design and material emerges at the lance end. The actual tip position therefore determines where injection starts, not merely the length visible above ground.

Select installation and opening methods for ground conditions and the specific system. Arrows indicate material exit directions; the yellow shape remains an illustration of the intended zone. In practice, the migration path is shaped by soil, voids, water and confinement of expansion.

Confirm tip depth and a clear outlet.
Record actual injection into each zone.

HAMMPACK lance systems →Confined expansion and the effect in the ground →

Lance with a perforated section beneath the foundation; several arrows indicate lateral material discharge. — The outlet zone should lie within the layer covered by the method.

06 · Material outlet method

Lance option: injection through a perforated section

The perforated section creates several material exit paths. Its position and length must correspond to the working layer; the lance tip alone reaching the desired depth is insufficient. Hole positions do not guarantee uniform injection distribution in every soil.

If the objective is a water barrier, acceptance must cover zone continuity and watertightness. Select SoilConsolid for the assessed soil and water conditions. GeoPolymer.55 may be considered for such a barrier after individual selection and a continuity and watertightness trial, with expansion and migration control; the yellow shape in the diagram alone does not confirm the result.

Place all outlets in the target zone.
Accept the result according to the injection objective.

SoilConsolid →GeoPolymer.55 →Cleaning systems after resins →

First explain the change in support

A cracking wall, settling floor and slab rocking under load do not automatically indicate the same problem. Possible causes include voids beside the structure, loose backfill, changed water conditions or a weaker layer deeper down. Assessment should cover the structure, ground, water and displacement history.

Collect foundation cross-sections, ground investigation results, service locations and level and crack measurements. Establish whether the process is ongoing. Without this, injecting material into the easiest accessible void may alter a local symptom while leaving the cause of settlement in another layer.

Define the expected effect

Ground consolidation and sealing

The material must act on an assessed ground zone, for example by bonding grains or limiting water flow. Selection depends on penetration potential and moisture conditions. Filling a void beneath a slab alone does not confirm consolidation of a deeper layer.

Void filling and restoring support

The objective is controlled occupation of the available space. Its connections must be identified and progress observed. During stabilisation, unintended structural lifting is a signal to stop.

Controlled lifting

Here, lifting is an intended part of the design. It requires a target level, allowable differential movements, sequence and stopping thresholds. Resin consumption does not replace movement measurements.

Reducing water ingress

A water barrier has different criteria from improved support. If ingress behind a wall is the problem, compare the solution with an injection curtain and assess possible paths around the barrier.

Expansion is a tool, not the repair result

Resin expanding in a confined space behaves differently from foam freely rising in a vessel. The ground and loaded structure restrict growth. The free-foaming factor is therefore insufficient to calculate consumption or lifting force.

The strength of a material specimen is not the bearing capacity of the entire ground–foundation system. Changes in support also depend on material distribution, ground condition and structural interaction. Selection should specify how the effect will be checked in the ground and on the structure.

The lance must deliver material to the right layer

Plan injection points in cross-section and plan view. Select access from inside or outside, accounting for services, foundation edges and the required working level. The arrangement of successive depths should follow the selected method, not just available lance length.

An open end, a tip opened during injection and a perforated section create different material exit paths. Select the lance system for the zone to be treated and installation conditions. The geometry calculator helps determine access; it does not identify the layer requiring improvement.

A reference section combines injection with measurement

Before starting, establish reference points and initial readings. The trial should check injection, communication, quantities and structural response under representative conditions. Record material, temperature, portions, time, pressure and displacements.

Inject in stages defined by the method, allowing time to assess the response. Expansion may continue after the pump stops. Stop for unintended movement, uncontrolled discharge, unusual uptake or a pressure rise without flow. Set stopping and resumption criteria before the trial, not only after observing displacement.

Acceptance must match the objective

For stabilisation or ground improvement, the design defines how achieved support is assessed and which tests are required. For lifting, document levels, differential movements and adjacent element behaviour. For a water barrier, check flow and continuity of the sealed zone.

Retain records of points, depths and quantities with measurements before, during and after the works. Plan observation over a period appropriate to the settlement cause and water changes. Returning to level is not itself proof that the cause of lost support has been removed.

RESINBAU SELECTION

Site conditions determine the material

SoilConsolid →

Consolidation and water barriers in assessed ground. The PU system with catalyst requires water to react and is delivered through one line; low viscosity does not guarantee penetration of every soil.

GeoStabil →

Ground stabilisation and grouting beneath slabs. The two-component material forms a semi-rigid mass; the TDS declares no foaming. Selection includes working time and delivery arrangement.

GeoPolymer.55 →

Two-component foam system for designed filling, stabilisation and lifting. Assess expansion effects under actual conditions with structural measurements.

GeoPolymer.350 →

Higher-density foam system for assessed voids and stabilisation. Selection between it and GeoPolymer.55 follows the design and TDS parameters, not merely the name or free foam volume.

Calculate what you know

CALCULATORAccess geometry beneath a foundation →

Determine lance length and position for a specified zone. The tool does not calculate bearing capacity or lifting magnitude.

CALCULATORMaterial preparation →

Check the correct product and ratios. A mass ratio need not equal a volume ratio.

CALCULATORConsumption quantities →

Convert portions of the correct components; keep a separate record of ground trial results.

Next step

Select the design and outlet positions for the method.

Discuss your project conditions

Prepare a cross-section, a description of water and movement, and results of previous trials. ResinBau helps select the material and application method.

Discuss your project / technical selection ↗