Stonewalls

Drystone Lidar Measurements

Measuring, documenting and monitoring deformations on dry stone walls

When inspecting existing dry stone walls, it can be important to be able to measure the deformation of the visible surface as precisely as possible. If the measurements are repeated at regular intervals, it is possible to check whether the deformation is progressing, for example whether a bulge is getting bigger. Professional 3D scanners are prohibitively expensive for normal dry masons. A DIY scanner has therefore been developed that delivers sufficiently accurate 2D results. This 2D scanner can be used to capture both vertical and horizontal profiles on dry stone walls.

A commercially available 2D lidar with a range of 30m is used. It is suspended vertically on a gimbal joint. As the laser of the lidar is not visible, a small cross line laser is added for precise positioning. The whole system is mounted on a tripod and can be used in the field.

The data from the Lidar measurements can be visualized with a CAD program.

Paving with local river stones / 2022

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SIA code of practise 2053 "Drystone masonry in natural stone"/ 2015 - 2020

Participation in the team for the conception and elaboration of the code of practise SIA 2053 / 2020 D "Dry masonry in natural stone"

The code of practice SIA 2053 has evolved from the guidelines for the construction of dry masonry walls. The main goals were the integration in the system of existing SIA standards for natural stone masonry and the provision of a basis for planning, tendering and quality assurance of drystone walls.

SIA Code of Practice: Dry stone walls: construction techniques, conservation and ecology

With the replacement of the standard SIA 178 (natural stone masonry) by the new standards SIA 266/2 (natural stone masonry) and 269/6-1 (conservation of natural stone masonry), the specifications in the set of standards of the SIA were brought up to date. The dry stone masonry could not be duly taken into account in the process.

Dry stone walls play a decisive role in shaping our cultural landscape. These walls are found in large numbers in vineyards, as field boundaries, in railroad and road construction or as avalanche barriers. Quite a few such wall landscapes are already under protection. It is an old stock - after 1935 practically no dry stone walls were built.

It is a peculiarity of dry stone walls that they can practically only be "repaired" by means of partial and full replacement - i.e. if one wants to keep these buildings, the construction method and associated craft must be maintained. An SIA leaflet with the above-mentioned title would be of decisive help in this respect. On the one hand, the rules of this construction method could be laid down throughout Switzerland, and on the other hand, a means of quality assurance would be created, from tendering to execution.

There is good, new technical literature on dry stone walls. However, since the repair of dry stone walls has to be financed more and more by public sources, a compact, overarching set of rules is welcome for all sides.

The code of practice can close gaps in content. The standards SIA 266/2 (natural stone masonry) and 269/6-1 (conservation of natural stone masonry) could not address the issue of ecology. In the case of dry stone masonry, this is much more possible and also makes more sense. It could be outlined how far vegetation is permissible in terms of construction and where limits exist. Conversely, the construction method could be specifically propagated to improve ecological connectivity. Requests from BUWAL in this regard could not be taken into account at the time 269/6-1 was drawn up.

Topics in the SIA 2053 code of practice

Preservation of regionality
The goal of the code of practice is to preserve the regional diversity/property of dry stone walls. The construction rules for achieving maximum stability and durability are universal. Locally, there may be deviations from these rules, for example, due to the lack of weather resistance of the local stone material or as a result of the lack of long ties or capstones. In this case, it is important for both the client and the executing craftsman that it is precisely defined where deviations from the generally applicable construction rules occur.

Ecology / Protection and promotion
An important reason for the preservation and new construction of dry stone walls is the recognition that dry stone walls provide important habitats for many endangered plant and animal species. This fact sheet identifies points in the inventory planning and construction process that are important for preserving the ecological value of dry stone walls. It lists the legal basis and refers to planning instruments for the validation and protection of dry stone walls.

Statics of dry stone walls
The load-bearing capacity of dry stone retaining walls can be calculated. If the rules of the masonry association are observed and the workmanship is perfect, the load-bearing capacity of dry stone retaining walls can be verified. This leaflet shows which rules must be observed when building retaining walls of dry stone masonry and which rules must be applied in the calculation.

Verifiable construction rules / quality assurance
The leaflet lists the rules for the various construction methods of dry stone masonry. This makes it possible to ensure that it is clear to all parties involved in the planning, submission and execution phases which masonry is being planned and executed.

Tendering
The leaflet provides instruments for carrying out tendering for drystone masonry. This enables a clear definition of the desired construction method and makes the comparison of different offers possible.

Inventar Schwyz 2019

Drystone walls as plans / drawings

Drawing up a plan of a dry stone wall for documentation, inventory, project planning, quality assurance and dimensioning. The example shown was created with the CAD software "Sketchup".

The following example shows the steps required to create such a plan. In the finished plan, the wall surface with individual stones is visible. This makes it possible to compare the views of the wall before and after renovation. The location of the long through stones can also be documented.

Download the example plan as a PDF:

plan_2dganz.pdf

Capture the three-dimensional structure of the wall using a tachymeter, photogrammetry or GPS data. With the help of these data, the wall can be represented spatially and dimensionally correct.

This representation can be used to identify areas, record the condition and the need for renovation.

In order to have an overview of the entire wall surface, it is advantageous to flatten the 3d representation as a 2d surface. For this purpose, the three-dimensional data is displayed as a surface. The measures (areas, distances) remain unchanged. For further processing, the 2d drawing is divided into sections of 2m width.

A measuring tape is laid out in the field in front of the wall. A picture of the wall surface is taken in sections of 2m.

Example of a single image. The position of the starting and ending point of the 2m is marked for clarification. A vertically placed metre can also be photographed as a scale.

As a check and supplement, the heights of the dry stone wall at the beginning and end of the 2m sections can be noted.

The single image is now inserted into the plan as a texture and placed correctly in terms of scale. The markings for the start and end points of the 2m section and the vertically positioned metre help .

With the described procedure, plans can be made before and after a renovation. It is possible to document the location of the long through stones and to show the rebuilt area on the plan.