Mass Stabilization as a Ground Improvement Method for Soft Peaty

Construction of road embankments or other infrastructures on soft peat is a challenge. The main problems are high compressibility and rather low undrained shear strength of peat. Mass stabilization provides a solution to improve the properties of a peaty subgrade. Mass stabilization is a ground improvement method, where hardened soil mass is created by adding binder into soil and by controlled in situ mixing. Mass stabilization poses an alternative solution for conventional mass replacement or other techniques, which leave peat in place. The chapter deals with mass stabilization of soft peat soil. Specific attention is paid to design, research and construction considerations, and experience obtained during last three decades. Peat properties before and after stabilization, design methods including pre-testing, stabilization technique and machinery, quality control methods and practices, binder technology, long-term performance of mass stabilized peat, environmental effects, feasibility, applications, and limitations are all presented and discussed in this chapter. The long-term observations (during the last 25 years) have shown that the strength of stabilized peat has continued to increase in average 1.6 times from the strength of 30 days. Therefore, mass stabilization has proven to be a flexible ground improvement method for peat layers with maximum thickness of 8 m

USA Hockey body checking rule change : comparison of contact situations between 12U and 14U USA Hockey Nationals Tournament

Body checking has been the most talked about subject in the field of ice hockey for the past years. National ice hockey associations have lately reviewed their body checking rules, one of them being USA Hockey, second largest national association in the hockey world. USA Hockey saw a noticeable dropout rate in the age categories where body checking was introduced and allowed (12 and under). For the season 2011-2012, USA Hockey decided to remove body checking from 12U ice hockey, still allowing body contact, raising the age of “full contact”(body checking) hockey to 14U. The goal of the rule change was, gradually introduce body checking to the players and retaining young athletes in the sport, focusing on educating the players and coaches, but at the same time keeping certain level of physicality in the game. USA Hockey wanted to do a research to find out if the players are used to the new rules and if the game is still physical, whitin the new rules. Data was recorded at the end of the season in the National tournaments in 2012, comparing the severity of contact and the rate of change of puck possession, in both 12U and 14U, hoping to see the effects of the rule change. After the data was analyzed, the results showed that at both of the age groups, there was a similar amount of contact situations recorded, with the main finding being that the players in 12U were used to the newly implemented rules, performing less severe contact with the opponent. USA Hockey is really pleased with the effects of the rule change, as in the following years they have seen increase in retaining the players in the sport, as well as insurance companies being happier with having to handle fewer injuries in the age groups

Long-term functionality of mass stabilization

Massastabiloinnin pitkäaikaistoimivuutta ei ole aiemmin tutkittu laajamittaisesti. Massastabiloinnin pitkäaikaistoimivuudella tarkoitetaan massastabiloinnin painumien, stabiliteetin sekä kantavuuskestävyyden pitkäaikaista hallintaa. Massastabiloidun materiaalin lujuus vaikuttaa merkittävästi näihin ominaisuuksiin. Tämän työn tavoitteena oli tutkia massastabiloinnin in situ -lujuuden keskiarvon ja hajonnan muutosta ajan suhteen sekä löytää perusteita havaituille muutoksille. Selvityksen perusteella arvioitiin massastabiloinin pitkäaikaistoimivuutta pääosin lujuuden kehittymisen kannalta. Arvio tehtiin erilaisille side- ja runkoaineille 6,5-25 vuoden kuluttua massastabiloinnista. Tutkimusaineisto kerättiin suorittamalla uusia tutkimuksia työhön valituissa yhdeksässä kohteessa sekä selvittämällä kohteiden aiemmat laadunvalvontatulokset. Tämän työn yhteydessä tutkittiin yhteensä 18 runko- ja sideaineyhdistelmältään erilaista massastabiloitua osa-aluetta. Tutkittuja runkoaineita olivat turve, ruoppausmassa sekä savi. Tutkimusaineisto jaettiin 0,5 m syvyysväliä edustaviin otoksiin, joita käsiteltiin tilastollisin mentelmin. Otoksille laskettiin syvyysväliä kuvaavat tilastolliset perusarvot, kuten keskiarvo ja hajonta. Tilastollisia perusarvoja verrattiin vastaavan syvyysvälin arvoihin eri ajanhetkinä, jolloin saatiin arvio lujuuden muutoksesta ajan suhteen. Vertailu suoritettiin ensin kohteen sisällä eri ajan hetkinä ja tämän jälkeen eri kohteiden välillä, jolloin havaittiin side- ja runkoainetyyppien ominaispiirteitä lujuuden kehittymisen suhteen. Tuloksista laadittiin laaja tietokanta, jota on tarkoitus hyödyntää myös jatkotutkimuksissa. Tulosten perusteella todettiin lujuuden kasvaneen ajan suhteen runko- ja sideaineesta riippumatta. Hydraulisilla sideaineilla massastabiloitujen kohteiden lujuuden kehittyminen oli pozzolaanisilla tai kipsipitoisilla sideaineilla massastabiloituja nopeampaa, mutta n. 10 vuoden jälkeen voitiin todeta lujuuksien kasvaneen kutakuinkin yhtäläisesti riippumatta sideainetyypistä. Lujittumisajan ollessa 6,5-25 vuotta, lujuus oli kasvanut hydraulisilla sideaineilla massastabiloiduissa kohteissa keskimäärin 1,6 kertaiseksi ja pozzolaanisilla tai kipsipitoisilla sideaineilla 2,0 kertaiseksi verrattuna kuukauden ikäisen massastabiloinnin lujuuteen. Suoritettujen tutkimusten perusteella massastabiloinnin pitkäaikaistoimivuus paranee lujuuden pääsääntöisesti kasvaessa työssä tarkastellulla 25 vuoden havaintojaksolla.The long-term functionality of mass stabilization has not been studied on a large scale. The long-term functionality means controlling settlements, stability and bearing capacity in a long-term. The strength of the mass stabilized material has a significantly impact on these properties. The main goal of this thesis was to examine the change of mean and dispersion of mass stabilization in-situ strength in relation to time and find reasons for the findings. The long-term functionality of mass stabilization was studied mainly from the perspective of long-term strength development. The study was done to different binder mixtures and soil mass types 6.5-23 years after the mass stabilization. The research data was collected by performing new investigations and gathering previous quality control results from the chosen nine mass stabilization sites. In pursuance of this thesis, in total of 18 sections, each differing by binder or soil mass type, were studied. Studied soil types were peat, dredged sediment and clay. The research data was divided into samples which represented 0.5 m depth range of the mass stabilized block. The samples were then analysed using statistical methods. As a result i.a. mean values and dispersions of the samples were calculated. The calculated values of the depth range were compared to the values of the same range at different times to evaluate the change of the values in relation to time. The evaluation was first done within the studied section and after that using all the data gathered from all of the sections to find the long-term strength development properties of a specific binder or soil type in general. In addition, a large database was built up to ensure that the results can be exploited in the future studies. As a result it was found that the strength of the mass stabilization had increased regardless of binder or soil mass type. The short-term strength development was observed to be faster on hydraulic binders when compared to pozzolanic or gypsum binders, where as after 10 years from mass stabilization the strength had increased almost equally compared to the strength observed 30 days after the stabilization. In the period of 6.5-23 years the strength had increased with hydraulic binders on average 1.6 times and pozzolanic or gypsum binders 2.0 times from the 30-day-strength. As a result of this study, it can be concluded that the long-term functionality of mass stabilization increases as time goes on, as the strength increases in the period of 25 years examined in this stud