Ground Improvement Measures Research Articles

Use of in-situ tests like flat plate dilatometer (DMT) andSeismic Dilatometer (SDMT) vis-à-vis finite element-based software to examine the efficacy of ground improvement work at a high rise residential project in Kolkata

ABSTRACT Rapid urbanization in India, particularly in Kolkata, has led to a scarcity of suitable land, necessitating effective ground improvement techniques. A case study was evaluated using 500mm diameter, 10m long plain cement concrete (PCC) piles installed at 2m c/c spacing to enhance subsoil for a high-rise residential structure. Initial Dilatometer (DMT) tests showed the subsoil was unsuitable for shallow foundations. Post-PCC piling, DMT tests revealed a 30-40% improvement in subsoil stiffness. The factor of Safety against liquefaction was calculated using DEEPSOIL software. Further analyses with DMT Settlement software and PLAXIS 2D confirmed that post-piling, the raft foundation settlement remained within permissible limits, proving the effectiveness of the ground improvement measures.

Performance evaluation of high energy dynamic compaction on soil-rock mixture geomaterials based on field test

Dynamic compaction (DC) is an efficient ground treatment technique that has been widely used for different soil types, however, the investigation on performance of high energy level DC for soil-rock mixture backfills is rare so far. This study presents a field investigation of the effectiveness of DC with a maximum energy level of 10,000-kN·m on soil-rock mixtures in southwestern China. Field tests, including surface wave test (SWT), super heavy dynamic penetration test (SH-DPT), and plate load test (PLT) were conducted to evaluate the effectiveness of DC under different conditions. The effectiveness and improvement depth were discussed based on SWT and SH-DPT. The results showed that the ground bearing capacity increased significantly after DC treatment both under non-soaking and soaking conditions. For the testing site with a fill thickness of 10 m, the allowable ground bearing capacity exceeded 300 kPa after DC treatment. The deformation modulus was measured to be 15 MPa. However, the impact of DC on the site with a fill thickness of 30 m is limited, and additional ground improvement measures are required for design.

Evaluation of Discharging Surplus Soils for Relative Stirred Deep Mixing Methods by MPS-CAE Analysis

Most of the ground in Japan is soft, leading to great damage in the event of liquefaction. Various ground-improvement measures are being taken to suppress such damage. However, it is difficult to carry out ground-improvement work while checking the internal conditions of the ground during the construction. Therefore, a visible and measurable evaluation of the performance of the ground-improvement work was conducted in this study. The authors performed a simulation analysis of the relative stirred deep mixing method (RS-DMM), a kind of ground-improvement method, using a computer-aided engineering (CAE) analysis based on particle-based methods (PBMs). In the RS-DMM, the “displacement reduction type (DRT)” suppresses displacement during construction. Both the DRT and the normal type (NT) were simulated, and a visible and measurable evaluation was performed on the internal conditions during each construction, the quality of the improved body, and the displacement reduction performance. As an example of these results, it was possible to visually evaluate the discharge of surplus soil by the spiral rod attached to the stirring wing of the DRT. In addition, the authors succeeded in quantitatively showing that more surplus soil was discharged when the stirring wing of the DRT was used than when the stirring wing of the NT was used.

Predicting the Time-Dependent Settlement for Multi-Layered Foundation Concerning the Coupling of Settlement Zones and Layers

The major part of this paper is on the challenges in predicting settlements in highway embankments and reclamation works in marine, deltaic and estuarine type of deposits. The emphasis is on practical aspects and the difficulties experienced in confidently estimating settlements even after a century of developments and contributions. The influence of the general geology and soil conditions is discussed in relation to the site investigation works and the establishment of soil profile models. The fundamentals of preloading techniques with and without prefabricated drains (PVD) as ground improvement measures are also included. The observational approach in evaluating PVD performance and settlement estimations is then made with emphasis on curtailing residual settlements. Finally, the latter part of the paper is devoted to the analytical and numerical solutions of the behaviour of piled supported approach embankments with transfer layers. Geogrid reinforced pile supported (GRPS) embankment system is studied with the analytical approaches of Terzaghi, BS8006 method and Hewlett and Randolph method. Additionally, numerical analyses are also made with the Plaxis software.

Train-Induced Building Vibration and Radiated Noise by Considering Soil Properties

Constructing buildings above subway tracks exploits urban-area space intensively by adopting the three-dimensional overlapping development mode, which is one of the important measures for solving the contradictions among urban population increase, land resource shortage, and environmental protection. However, the vibration generated by the frequent train operations is transmitted to the upper buildings through the track structure and ground soil, which can cause structural vibrations and radiated noise and bring physical and mental side effects to occupants within the buildings. Subway projects are often located in geologically sensitive areas, while the influences of the encountered geological problems on the generation and propagation of structural vibration and structure-radiated noise within the buildings are not yet clear. Hence, this paper presents a method of studying the train-induced vibration transmission from the ground up into the buildings and the structure-radiated noise within the building. The method consists of a train-track model, track-soil-building model, and structure-radiated noise simulation. The impact of soil properties on the building vibration and structure-radiated noise is analyzed and ground-improvement measures are proposed in order to mitigate vibration and structure-radiated noise within buildings. The results show that the interaction between soil and structure has a great impact on vibration transmission from the ground into the building. Good foundations reduce vibration transmission from ground soil up into the building and lead to a lower level of structure-radiated noise. Ground improvements increase the impedance of ground soil, thereby weakening the vibration transmission and lowering the structure-radiated noise.

St. Kanzian tunnel chain – Current state of works

AbstractThe railway line from Graz to Klagenfurt, section Mittlern–Althofen/Drau, is part of the Austrian high‐speed network and a partial section of the trans‐European railway network (TEN in the EU, Pan‐European corridor in the eastern countries). With the Koralmbahn line from Graz to Klagenfurt, capacity on the north‐south connection Vienna–Tarvis will be considerably increased and the journey times noticeably shortened. The St. Kanzian tunnel chain is the most important part of the section Mittlern‐Althofen/Drau in southern Carinthia, in the immediate vicinity of the tourist region of Klopeiner See/St. Kanzian. The St. Kanzian tunnel chain consists of six tunnels with lengths between 230 and 2,100 m, which are under construction by various methods. Despite the short distances between the tunnels, the inhomogeneous geological conditions ranging from silty‐sandy lacustrine sediments to phyllites are a great challenge. The topography also leads to consistently shallow overburden. The stated conditions lead to the necessity of extensive specialised civil engineering and ground improvement measures.

SOIL REINFORCEMENT USING CALCIUM PHOSPHATE COMPOUNDS

For the purpose of using calcium phosphate compounds (CPCs) for ground improvement measures, such as the reinforcement of soils and rocks, a fundamental examination of new grouting materials composed of CPCs (CPC-Chem) is required. Therefore, in this study, we have first analyzed the ideal conditions for CPC precipitation by in vitro examination of the different mixtures of calcium and phosphate stock solutions. Following that, Toyoura sand was cemented with CPCs and the cured specimens were analyzed by using unconfined compressive strength (UCS) tests. Similarly, Toyoura sand was cemented with a mixture of CPC-Chem and tricalcium phosphate (TCP) powder and then cured; these specimens too were then analyzed by using UCS tests. Test results indicate an improvement in UCS of TCP-added specimens when compared to that of no-additive (CPCChem alone) specimens. Besides, the morphology and elemental composition of the specimens were analyzed by using scanning electron microscopy (SEM) and energy dispersive X-ray fluorescence spectroscopy (EDX). The results obtained from the systematic analyses indicate the practical feasibility of using both the combination of CPC-Chem and TCP powder as well as the CPC-Chem alone as chemical grouts for ground improvement measures.

Unique Grout Material Composed of Calcium Phosphate Compounds

To employ calcium phosphate compounds (CPCs) in ground improvement measures such as the reinforcement of soil and rock, we examined suitable conditions for CPC precipitation and performed unconfined compressive strength (UCS) tests of sand test pieces cemented by CPC. Two types of phosphate stock solution and two types of calcium stock solution were used to prepare the reaction mixtures and CPC precipitation was confirmed in all reaction mixtures. The volume of CPC precipitation in the mixture increased as the pH rose from strongly acidic to around neutral. The UCS of sand test pieces cemented by 1.5 M diammonium phosphate and 0.75 M calcium acetate tended to increase with time, reaching a maximum of 87.6 kPa. The results indicate the practical feasibility of using unique and new CPC grouts as chemical grouts because of their self-setting property and as biogrouts because of the pH dependence of precipitation.

Assessment of frozen-ground conditions for engineering geology along the Qinghai–Tibet highway and railway, China

The Qinghai–Tibet Highway and Railway (the Corridor) across the Qinghai–Tibet Plateau traverses 670 km of permafrost and seasonally frozen-ground in the interior of the Plateau, which is sensitive to climatic and anthropogenic environmental changes. The frozen-ground conditions for engineering geology along the Corridor is complicated by the variability in the near-surface lithology, and the mosaic presence of warm permafrost and talik in a periglacial environment. Differential settlement is the major frost-effect problem encountered over permafrost areas. The traditional classification of frozen ground based on the areal distribution of permafrost is too generalized for engineering purposes and a more refined classification is necessary for engineering design and construction. A proposed classification of 51 zones, sub-zones, and sections of frozen ground has been widely adopted for the design and construction of foundations in the portion of the Corridor studied. The mean annual ground temperature (MAGT), near-surface soil types and moisture content, and active faults and topography are most commonly the primary controlling factors in this classification. However, other factors, such as local microreliefs, drainage conditions, and snow and vegetation covers also exert important influences on the features of frozen ground. About 60% of the total length of the Corridor studied possesses reasonably good frozen-ground conditions, which do not need special mitigative measures for frost hazards. However, other sections, such as warm and ice-rich or -saturated permafrost, particularly in the sections in wetlands, ground improvement measures such as elevated land bridges and passive or proactive cooling techniques need to be applied to ensure the long-term stability of thermally unstable, thick permafrost subsoils, and/or refill with non-frost-susceptible soils. Due to the long-history of the construction and management of the Corridor by various government departments, adverse impacts of construction and operation on the permafrost environment have been resulted. It is recommended that an integrated, executable plan for the routing of major construction projects within this transportation corridor be established and long-term monitoring networks installed for evaluating and mitigating the impact from anthropogenic and climatic changes in frozen-ground conditions.

Seismic retrofit of George Massey Tunnel

AbstractThe 629 m long immersed George Massey Tunnel passes under the south arm of the Fraser River near Vancouver, British Columbia. The tunnel was completed in 1959. Based on current seismic design standards, the precast concrete structure is grossly under‐reinforced in the longitudinal direction. Buckland & Taylor Ltd was retained by the Ministry of Transportation of British Columbia to conduct a seismic assessment and final design for the seismic safety retrofit of the tunnel. A number of vulnerabilities were identified including soil liquefaction in the loose jetted sand and native deposits underneath the tunnel, resulting in tunnel flotation, large differential lateral displacements, and post‐liquefaction consolidation settlements, subsequently imposing large tensile and compressive forces in the weak tunnel joints. The situation of cracking and water leakage potentially creates a life hazard in the event of a major earthquake. During the final design, detailed non‐linear dynamic geotechnical analyses were conducted to study the effects of soil liquefaction and to evaluate ground improvement measures. Detailed structural analyses were also conducted considering different proposed retrofit schemes to enable the tunnel section to handle the soil displacement demands. Centrifuge model testing was used to calibrate and verify the liquefaction characteristics predicted by the numerical models and the proposed densification and gravel drainage techniques. Field testing of gravel drains was performed to collect data on the performance of different types of gravel drains. Copyright © 2005 John Wiley & Sons, Ltd.

Possible role of ground improvement measures in mitigating the Chernobyl environmental disaster

This technical note reports on the many deaths and illnesses suffered by geotechnical engineers who worked in the immediate aftermath of the Chernobyl nuclear power station explosion in 1986. It recommends that postaccident geo-environmental protection works should only be undertaken after a site has been made safe by specialist damage control teams. It also recommends that geoenvironmental protection measures should be implemented on all existing and future nuclear projects before waiting for an accident to happen.